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\begin{center}
{\large VOLKSWAGEN-STIFTUNG KOOPERATIONSPROJEKT}

\vspace{2.5cm}
{\Large\bf Light scattering by small particles:}

\smallskip
{\Large\bf new methods and techniques}
\end{center}

\vfill

\noi
{\bf Astrophysical Institute and University Observatory, 
     Schiller\-g{\"a}{\ss}chen 2--3, D-07745 Jena, Germany}

\smallskip
Prof.~Dr.~Th.~Henning (project head),
Dr.~O.~Fischer,
Dr.~B.~Michel,

Dr.~H.~Mutschke,
Dr.~R.~Stognienko

\bs
{\bf Astronomical Institute, St.~Petersburg University, 
     St.~Petersburg, \\
     198904, Russia}

\smallskip
Dr.~habil.~N.V.~Voshchinnikov (project coordinator),
Dr.~V.B.~Il'in,

M.Sc.~N.A.~Krivova,
M.Sc.~V.V.~Somsikov

\bs
{\bf Physical Institute, St.~Petersburg University, 
     St.~Petersburg, \\
     198904, Russia}

\smallskip
Prof.~Dr.~L.S.~Ivlev,
M.Sc.~A.V.~Vasilyev

\bs
{\bf St.~Petersburg Academy of Aerocosmic Instrumentation, \\
     St.~Petersburg, 198904, Russia}

\smallskip
Prof.~Dr.~V.G.~Farafonov,
M.Sc.~O.Yu.~Shultz

\newpage
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\tableofcontents

\subsection*{Attached Documents}
\begin{enumerate}
\item	Stellungnahme der Leitung des deutschen Instituts zum Projekt
\item	T{\"a}tigkeitsberichte 1995, Astrophysikalisches Institut 
	und Universit{\"a}ts-Sternwarte Jena und 
	Max-Planck-Gesellschaft, Arbeitsgruppe ``Staub in 
	Sternentstehungsgebieten'', Jena: Sonderdruck aus 
	``Mitteilungen der Astronomischen Gesellschaft'', Band 79
\item	Curriculum vitae and publication list of the German scientists
\item	Curriculum vitae and publication list of the Russian scientists
\item	Scientific program of a joint workshop
\end{enumerate}

\newpage
\thispagestyle{empty}
\addcontentsline{toc}{section}{Zusammenfassung}
\mbox{}

\newpage
\section{Project description}

\subsection{Project goals and expected results}\label{goals}

The specific goals of the project are the development of new 
theoretical approaches and numerical codes in the field of 
light scattering by non-spherical and/or inhomogeneous particles 
(Sect.~\ref{theory}), 
the collection and analysis of the optical constants measured 
for different materials (Sect.~\ref{database}), 
and the application of both the techniques developed and the 
laboratory data considered to scientific and engineering problems 
(Sect.~\ref{astro_appl}--\ref{engee_appl}).

\ms
The project consists of three parts:

\smallskip
\noi{\it  A. Light scattering theory.}

A sophisticated approach to calculate the spheroidal wavefunctions 
will be developed.
It should revive a basic method of the light scattering theory---the 
separation of variables method.
The computer code to be written will be able to treat scattering by 
very large layered spheroidal particles.

An advanced method for axisymmetric particles will be created, 
involving the ideas of the separation of variables and T-matrix 
methods.
It will be based on a superposition of special scalar potentials: 
those for spheres and cylinders and those for disks.
The method will allow an efficient treatment of particles whose 
shape essentially deviates from the spherical one.

A new statistical method to describe the optical properties of 
ensembles of randomly oriented non-spherical particles will be developed.
It will be in particular efficient for irregularly shaped grains 
and particles which consist of highly absorbing materials.
On the basis of the distorted dyadic Green function being used in 
the method, a numerical approach to calculate scattering by 
inhomogeneous spheres will be produced as well.

A comparative analysis of different approaches to calculations of 
the scattering properties of spheres, spheroids, finite cylinders,
composite particles, agglomerated and coagulated particles will be 
made.
It will include an outline of the area of the approaches' 
applicability and of the main features of light scattering 
by the particles of each type.

\smallskip
\noi{\it B. Laboratory data analysis.}

It is intended to collect the refractive indices of various 
silicates, oxidic and carbonaceous materials, metals, ices, 
liquids, etc.\ available in the literature.
The data will be uniformly tabulated in electronic form and 
supplied with the information how they were obtained in the
laboratories, how reliable they are, how they were processed, 
etc.

\smallskip
\noi{\it C. Scientific and engineering applications.}

The numerical techniques and the optical constant database 
to be created will be used for interpretation of recent 
astrophysical observations of interstellar and cometary 
dust, consideration of light scattering in atmospheric 
clouds of different origin and for elaboration of a 
laboratory method.

\newpage %\bs
The {\it main results} of the work on the project will be: 
\begin{itemize}
\item	an efficient numerical code based on the separation of 
	variables method;
\item	a new method and computer code for the calculation of optical 
	properties of strongly non-spherical (but axisymmetric) 
	layered particles;
\item	a statistical approach and code for the simulation of light 
	scattering by an ensemble of randomly oriented irregularly 
	shaped particles;
\item	a comparative review of the current approaches to treat the 
	light scattering by non-spherical particles;
\item	a database with optical constants of various materials that 
	will be available via Internet (anonymous FTP, World Wide Web) 
	and CD-ROM;
\item	new knowledge on the properties of interstellar dust grains 
	obtained from the analysis of recent polarimetric and 
	photometric observations;
\item	conclusions on the characteristics of cometary dust grains 
	made from the interpretation of polarimetric and colour data;
\item	basic non-spherical models of atmospheric aerosols;
\item	a principal scheme of an optical device for measurements of 
	extremely low gas concentrations.
\end{itemize}

\subsection{Background and methods}

\subsubsection{Light scattering theory}\label{theory}

The theory of light scattering by small particles has a long history 
and numerous applications.
Many theoretical approaches and numerical techniques 
have been elaborated and utilized (H.C.\ van de Hulst, Light 
scattering by small particles, Wiley, New York, 1957;
C.F.\ Bohren \& D.R.\ Huffman, Absorption and scattering of light by 
small particles, Wiley, New York, 1983).
For non-spherical particles of finite sizes, three basic methods are 
in general used: 
the Separation of Variables Method (SVM), 
the T-Matrix Method (TMM) and 
the Discrete Dipole Approximation (DDA).
These methods are described, e.g., in the papers of
S.~Asano \& G.~Yamamoto (\ApplOpt {\bf 14}, 29, 1975),
P.W.~Barber \& C.~Yeh (\ApplOpt {\bf 14}, 2864, 1975), and
B.T.~Draine \& P.J.\ Flatau (\JOSA {\bf A11}, 1491, 1994).
Each of these methods has their restrictions.
The SVM can treat only spheroidal particles.
The TMM gives good results for axisymmetric particles but their shape 
should not strongly deviate from the spherical one.
The DDA is applicable to particles of any shape and structure but 
their size should not considerably exceed the wavelength of the 
incident radiation.

The standard dust models used in the applications of the light 
scattering theory, have been based on the particles of the simplest 
shapes:
homogeneous and core-mantle spheres and infinitely long cylinders.
The methods and numerical codes developed for non-spherical 
inhomogeneous particles of finite sizes allow extensive 
simulations only for rather small and/or optically soft 
particles deviating not substantially from spheres.
In many cases, however, the effects of the particle's shape and 
structure cannot be neglected.
The methods and the numerical technique to be developed in the 
project will be designed for the treatment of light scattering 
by inhomogeneous non-spherical particles with sizes and aspect 
ratios much larger than those possible by the currently available 
approaches.

In applications one often needs to average the scattering properties 
over many particles.
Usually, one first calculates the scattering properties of individual 
particles and then sums the results to obtain the ensemble averages.
An alternative approach which starts with ensemble-averaged 
quantities from the very beginning may be much more efficient 
in some cases.
Such a statistical approach will be developed which can be applied 
to the description of the optical properties of ensembles of randomly 
oriented non-spherical particles.

\ms
\underline{New approach to the Separation of Variables Method.}
\smallskip

The SVM is the most efficient method for spheroidal particles 
as it involves particle geometry as completely as possible.
However, there were only a few attempts to utilize the approach 
(see Voshchinnikov 1996\footnote{See the references to the project 
participants' papers at pp.~\pageref{Ref_start}--\pageref{Ref_end}} 
for a recent review).
Besides the complicated formulae, the applicability of the method to 
both homogeneous and coated spheroids is limited by the difficulties 
in calculations of the spheroidal functions for large values of the 
diffraction parameter (the ratio of the particle size to the radiation 
wavelength).
The main problems are the determination of the eigenvalues of the 
spheroidal functions and the proper choice of the expansion basis.

An advanced method to evaluate the eigenvalues of the prolate 
functions has been suggested by Voshchinnikov \& Farafonov~(1996).
Preliminary calculations have shown that it will work for large 
diffraction parameter values as well.
It is planed to realize numerically the method and to extend it 
to the oblate spheroidal functions.

Depending on the size and shape of particles, the spheroidal functions 
are usually expanded in terms of Legendre functions or Bessel 
functions.
In both cases, a fast loss of accuracy occurs during the computations 
for large particles.
The simplest way to solve the problem is to use extended precision 
in the calculations.
However, it causes an enormous growth of computational time.
In the project new ways in the calculation of the spheroidal functions 
will be gone: via solution of the corresponding differential equations 
and from the more general Heun functions.
The latter was recently suggested by W.~Lay 
%(Theor. and Math. Physics {\bf 101}, 360, 1994) 
(Ph.D.\ thesis, Stuttgart Univ., 1995).

\newpage\noindent%\ms
\underline{New method for axisymmetric particles.}
\smallskip

There are many modifications of the TMM which is very efficient 
for axisymmetric particles.
However, the principle limitation of the method remains 
its instability for the particles with a relatively strong 
non-sphericity.
There are some known ways how to increase the method capacity 
but they are either computational time consuming or work 
only in particular cases (see, e.g., M.I.\ Mishchenko et al.,
\JQSRT {\bf 55}, 535, 1996).

It is planed to develop a new solution to the light scattering problem 
for homogeneous and core-mantle axisymmetric particles which would 
be as efficient as the TMM and could overcome the defect.
The diffraction problem will be formulated in the form of the surface 
integral equations and the spherical wavefunctions will be used as the 
basic ones.
However, unlike in the conventional TMM, the incident, scattered and 
internal fields will be divided in two parts: the axisymmetric part 
(no dependence on the azimuthal angle) and the non-axisymmetric part; 
the diffraction problem will be solved independently for each part.
Specific scalar potentials shall also be selected: a superposition of 
the Debye and Hertz potentials for the non-axisymmetric part and the 
Abraham potentials for the axisymmetric one.
Such an approach has been successfully used in the realization of 
the SVM for spheroids (Voshchinnikov \& Farafonov 1993; Farafonov 
1994a).

The advantage of the new approach is the combination of the strong 
sides of two basic methods: 
the simple solution scheme typical of the TMM and the ability to treat 
extremely elongated or flattened particles as in the SVM.
The new method will allow to consider layered particles with a 
nontrivial structure (e.g., particles with an oblate spheroid 
as the core and a prolate spheroid as the mantle that is impossible 
in the SVM).

Note that both methods, the new SVM and the method for axisymmetric 
particles, will be {\em exact methods} to solve the scattering problem 
for specific particle geometries.

\ms
\underline{New statistical approach.}
\smallskip

There were only a few attempts to apply statistical methods in 
the light scattering theory (see, e.g., Michel 1995 for a review).
The most advanced approach---the Strong Property Fluctuations 
Theory (SPFT)---has been used for infinite or semi-finite media 
(e.g., the backscattering of wet snow and rocks) and for the 
calculation of the optical extinction by particles 
with simple aggregate structure.

In the project the SPFT will be used for simulations of the optical 
extinction and scattering produced by aggregates of overlapping spheres (as a model 
for coalescence) and inhomogeneous spheres (e.g., soot contaminations 
in water droplets, milk droplets, etc.).
Scattering and absorption will also be calculated in the framework of 
the SPFT by solving the so-called Bethe-Salpeter equation, which has 
not yet been done for particles.

On the basis of the distorted dyadic Green function, a numerical 
method will be developed to calculate scattering by inhomogeneous
spheres that reproduces scattering by a homogeneous sphere exactly.
Thus, only the deviations from homogeneity will be subject to the 
numerical treatment, which will reduce numerical errors considerably 
as compared to the standard methods like the DDA.

The additional advantage of the statistical method in comparison with 
standard approaches is that it is not restricted to optically soft 
particles.

\ms
\underline{Comparison of different methods.}
\smallskip

In the classical diagram by H.C.~van de Hulst (Light scattering by 
small particles, Wiley, New York, 1957), the theoretical approaches 
were considered and classified in the plane: refractive index vs diffraction parameter.
This analysis will be extended in the project by including the shape 
and orientation of the particles.
Various methods will be compared in detail through their accuracy, 
required memory and computational time.
As a result, the diffraction parameter--shape--refractive index 
limits will be outlined for the different approaches.
Some results will be presented in a tabular form to make them 
available as benchmarks.
Such a comparison of the current methods will allow to select the 
approach which would be optimal for the solution of a specific problem 
as well as to illuminate the lacunae in the theory.

\subsubsection{Database of optical constants}\label{database}

A lot of measurements of the optical properties of various materials 
have been done in laboratories in recent years.
The results are available in the literature for different quantities 
and in different formats (tables, pictures, etc.).
They have different accuracy, corresponding to special states of the 
materials, wavelength resolutions of the used devices, etc.
Nevertheless, to simulate optical effects, one often takes the data 
with a slight notion of their applicability.

In the project a database of optical constants will be created 
and made available via anonymous FTP, the World Wide Web, and CD-ROM.
The data will be presented in a unique format and supplemented by a 
description of the procedure of the sample selection and preparation, 
the method of measurements, the properties of the sample, etc.
Some additional tools (transformation of refractive indices to 
dielectric constants or to a special format, etc.) will be 
included as well.
It is planed to start filling the database by the optical constants of 
the materials important for astrophysical and atmospheric applications: 
silicates, oxides, ices, etc.
It should be noted that an essential source of optical constants 
is the laboratory of the Astrophysical Institute and University 
Observatory Jena.

\subsubsection{Astrophysical applications}\label{astro_appl}

The scattering theory has extensively been applied in astrophysics.
Information about astronomical objects is mainly obtained from the 
analysis of their radiation.
Dust grains in the Solar system, in the circumstellar and 
interstellar medium efficiently absorb, re-emit and scatter 
electromagnetic radiation.
This is observed, for example, in the interstellar extinction and 
polarization phenomena whose study, on the other side, allows to 
investigate the galactic dust playing an important role in 
interstellar matter chemistry and dynamics.

In the project the focus will be on the interpretation of the 
observations where the effects of the grain shape are dominant, 
i.e.\ the polarization data.
The inhomogeneity of the particles will be taken into account 
according to the contemporary physical models of interstellar 
grains including a refractory core and volatile or organic 
mantles (see, e.g., J.M.\ Greenberg, IAU Symp.\ No.~135, 
L.J.\ Allamandola and A.G.G.M.\ Tielens (eds.), Reidel, 
Dordrecht, p.~345, 1989).

\ms
\underline{Interstellar dust.}
\smallskip

The recent observations of the interstellar linear polarization 
in the infrared ($\lambda\lambda$ 2--5 $\mu$m) and ultraviolet 
($\lambda\lambda$ 0.13--0.30 $\mu$m) regions of the spectrum 
have greatly enlarged our knowledge about the wavelength 
dependence of the polarization (see, e.g., P.G.\ Martin et al., 
\ApJ {\bf 392}, 691, 1992 and G.C.\ Clayton et al., \ApJ {\bf 403}, 
722, 1995).
However, there is still a gap in the interpretation of the 
data---core-mantle non-spherical particles of finite sizes 
have not yet been applied.

It is planed to develop a model of polydisperse mixtures of partially 
aligned core-mantle spheroids.
The irregular shape of interstellar grains will be approximated 
by spheroids having a varying semiaxis ratio.
The model will also include the modern ideas about the grain alignment 
mechanisms (see D.C.B.\ Whittet \& W.\ Roberge (eds.), Polarimetry of 
the Interstellar Medium, 1996).
The multi-cloud structure of the interstellar medium for given lines 
of sight will be taken into account when possible.
The model will be aimed at the simultaneous interpretation of the 
interstellar extinction and linear polarization observations in the 
wide spectral range from the mid infrared to the far ultraviolet.

\ms
\underline{Cometary dust.}
\smallskip

The polarimetric studies of the solar light scattered by cometary 
dust grains have been performed at various phase angles $\alpha$ 
($\alpha = 0$, if the Sun, the Earth and a comet are located in a 
line, i.e.\ the solar radiation backscattered by cometary dust is observed).
They have provided information on the properties of the dust grains 
released from the cometary nucleus.
The discovered circular polarization of the P/Halley comet 
(K.\ Metz \& R.\ Haefner \AAp {\bf 187}, 539, 1987) and the 
non-zero linear polarization of some comets at $\alpha =0$ 
(G.P.\ Chernova et al., Icarus {\bf 103}, 144, 1993) 
undoubtedly indicate that the cometary grains are non-spherical 
and should be partly aligned.
Nevertheless, these circumstances have never been taken into account 
in the current models of cometary dust.

Using the model of core-mantle spheroidal grains and a simple model 
of the comets' vicinities---single scattering in an inhomogeneous 
coma---, it is up to the project to explain the observed wavelength 
dependence of the polarization and to clarify the nature of the phase 
variations of the polarization and colours.

\subsubsection{Atmospheric optics applications}\label{atmos_appl}

Atmospheric aerosols---the solid and liquid particles of natural 
or anthropogenic origin in the terrestrial troposphere and 
stratosphere---are a significant source of global climate 
forcing.
They interact with solar and thermal radiation as well as they 
affect in different ways other components of the climate system 
(see, e.g., R.J.\ Charlson \& J.\ Heintzenberg (eds.), Aerosol 
forcing of climate, 1995 for more details).

Many methods to investigate the aerosols have been used (see, e.g., 
K.Ya.\ Kondratyev (ed.), Aerosol and climate, 1991 for a review).
Now the optical methods based on the measurements and analysis of 
the scattering and extinction of the solar radiation are believed 
to be the most attractive.
To determine the properties of aerosols by such methods, efficient 
light scattering codes and appropriate models for aerosol particles 
are required.

Atmospheric aerosols may be divided into several groups depending 
on their origin, chemical composition, structure, etc.\ (see, e.g., 
G.A.\ d'Almeida et al., Atmospheric aerosols, 1991).
A large part of them---soil dust, sand event and soot particles and 
many others---are known to be essentially non-spherical.
There are also processes (e.g., condensation) which should result in 
layered particles.
However, the effects of the non-sphericity on the aerosol optical 
properties were discussed only in a few recent papers (e.g., M.I.\ 
Mishchenko et al., Geophys.\ Res.\ Lett., {\bf 22}, 1077, 1995).
Neither core-mantle spheroidal models nor statistical methods have 
been utilized in the field up to now.

\ms
\underline{Development of new aerosol models.}
\smallskip

The numerical techniques to be created within the project will be 
applied to simulate the scattering properties of non-spherical 
aerosols.
Calculations of the extinction and scattering cross-sections, albedo, 
and scattering matrices will be made for particles of various sizes, 
shapes, structures, and absorbing properties of their core and mantle.
Then a comparative analysis of the optical properties of both single 
particles and ensembles of aligned aerosols will be performed.

On the base of the calculations it is planed to develop the 
detection principles of non-spherical atmospheric aerosols 
and their microstructure and to estimate the aerosol shape 
effects on possible retrieval of the aerosol optical parameters 
from observational data and on the radiation balance in the 
terrestrial atmosphere.
%Optical experiments will also be suggested which
%could be used for the determination of the properties of aerosols.

\subsubsection{Engineering applications}\label{engee_appl}

The existing cheap and universal methods for the detection of gas 
components are applicable provided the fraction of an ingredient 
by mass is larger than $10^{-7}$--$10^{-8}$.
This limit could be lowered down to $10^{-9}$--$10^{-12}$ if the 
ingredient may be converted from the gaseous state to the solid 
one.
A good example could be the control of very low concentrations 
of ammonia (NH$_3$) that can be transformed to the chloride 
ammonia aerosols by the reaction: 
NH$_3 + $HCl$ \longrightarrow $NH$_4$Cl.
The latter substance forms elongated crystals which can be oriented 
by an electric field in special laboratory cameras (see Ivlev et 
al.~1993 for more details).
The replacement of the usual electro-optical approach by the much 
more sensitive optical one could lead to a significant progress 
in the area.

Based on calculations of the optical properties of spheroidal and 
cylindrical particles, it is planed to develop an express, cheap 
and universal method for the optical control of low concentration 
components.
Preliminary estimates show that the organic materials (e.g., various 
aromatic hydrocarbons) with the mass fraction as low as 10$^{-12}$ 
could be detected in the form of thin layers coating the spheroidal 
aerosols.

\subsection{Preliminary studies}

\subsubsection{Light scattering theory}

A new approach to the solution of the light scattering problem for 
homogeneous and coated confocal spheroids in the frame of the 
SVM has been suggested by Farafonov (1983, 1994a).
The main features of the scheme of the solution are: 
i)  the incident, scattered and internal fields are divided into two 
    parts: axisymmetric and non-axisymmetric ones;
ii) the scalar potentials for the solution of each part of the problem 
    are chosen in a special way.
In the subsequent papers, Voshchinnikov \& Farafonov (1993, and 
references therein), Farafonov (1994b), Voshchinnikov \& Farafonov 
(1994), Farafonov \& Voshchinnikov (1996), Farafonov et al.~(1996), 
and Voshchinnikov (1996) have developed the approach, created computer 
codes, and discussed the results of test calculations.
It was shown that due to the reasonable choice of the scalar 
potentials such an approach is more preferable from the 
computational point of view than the often used solution of 
Asano \& Yamamoto (\ApplOpt {\bf 14}, 29, 1975).

The SPFT has been tested thoroughly in the case of aggregates of 
touching spherical particles.
Its predictions have been found to be in a good agreement with the 
standard methods of the optical scattering theory (Michel 1995; 
Michel et al.~1996).
A generalization of the SPFT for non-homogeneous chiral media has 
been developed by Michel \& Lakhtakia (1995, 1996).

A comparison of the most popular methods (SVM, TMM, DDA) for 
non-spherical particles has been made by Voshchinnikov et al.~(1994b) 
and Hovenier et al.~(1996).
The statistic approach has been confronted with other effective 
medium techniques by Henning et al.~(1995b).

The optical properties of irregularly shaped porous dust grains have 
been studied with the aid of the DDA by Henning \& Stognienko (1993), 
Blum et al.~(1994), Stognienko et al.~(1995), Henning et al.~(1995b).
%The TMM has been used in the calculations of light scattering by
%spheroids for large diffraction parameter values
%by Il'in \& Henning (1996).

\subsubsection{Database of optical constants}

The careful analysis of the samples and detailed measurements of the 
optical constants of various materials (amorphous silicates, Mg/Fe 
oxides, Mg/Fe and Si sulfides, carbides, etc.) has been carried out 
in the spectral region from 0.2 $\mu$m to 100 $\mu$m at the Max Planck 
Society Research Unit ``Dust in Star-forming Regions'' which is now 
integrated in the Astrophysical Institute of the University Jena 
(the German side).
The results of the investigations have been published in the papers 
of Begemann et al.~(1994, 1995, 1996a, 1996b), J{\"a}ger et al.~(1994, 
1996), Dorschner et al.~(1995), Henning et al.~(1995a), Mutschke et 
al.~(1995).
Some data are already available via FTP and WWW (see 
http://www.astro.uni-jena.de).
The optical constants for many other materials have also been 
transferred from the tables and figures of the original papers 
to electronic form and used in calculations both in the Max 
Planck Society Research Unit and the Astronomical and Physical 
Institutes of the St.~Petersburg University (the Russian side).

\subsubsection{Astrophysical applications}

Some astrophysical applications of the model of homogeneous spheroids 
have been made in the papers of Voshchinnikov~(1990a, 1990b, 1990c).
They were based on the previous modelling of the interstellar 
extinction and polarization curves performed by Voshchinnikov 
et al.~(1986a, 1986b), Voshchinnikov \& Il'in~(1987) and 
Voshchinnikov~(1989) for the mixtures of partially aligned 
infinite core-mantle cylinders.

A sophisticated model of spheroidal interstellar grains has been developed by Il'in \& Henning (1996). 
The irregularly shaped interstellar dust grains were represented 
by an ensemble of prolate and oblate homogeneous spheroids with 
a distribution over their shapes, sizes and orientations.
The effects of the shape and the chemical composition of cosmic 
silicate grains on the optical properties of such ensembles have 
been considered and a comparison with the observational data 
available has been done.

\subsubsection{Atmospheric optics applications}

There are many different investigations of atmospheric aerosols 
done by the participants from the Russian side (see the books of 
Ivlev 1982 and Ivlev \& Andreev 1986 and references therein; 
Kondratyev et al.\ 1992, 1993, 1995; Ivlev et al.\ 1993; Andreev 
\& Ivlev 1995a,b, b; Andreev et al.\ 1995; Gavrilova \& Ivlev 1995, 
1996).
Below only those papers are mentioned which are most close to the 
project subject.

The analysis of the properties of dust particles in noctilucent 
clouds has been performed by Vasilyev et al.~(1989).
The measurements were made on the space satellites and have given 
the possibility to distinguish three main types of atmospheric 
aerosols:
sulfate core-mantle non-spherical particles with sizes up to 
0.5--0.6 $\mu$m, almost spherical compact particles with typical 
size $\approx 0.1 \mu$m, and the particles with small cores and 
volatile mantles.

Gavrilova \& Ivlev~(1991) investigated the influence of the 
properties of aerosol models on the ingoing and outgoing 
radiation fluxes at different levels at the atmosphere.
It was shown that the use of diverse aerosol models does not 
influence the angular dependence of radiation but changes 
significantly the values of absolute fluxes.

Modeling of the optical properties of core-mantle spherical aerosols 
was made by Ivlev \& Korostina~(1994).
They determined the limiting thickness of the mantle preventing the 
detection of the core from the optical measurements.
Andreev et al.~(1995) modelled and discussed the optical 
properties of fractal soot particles.

\subsubsection{Engineering applications}

The method to study the electro-optical properties of chloride ammonia 
(NH$_4$Cl) aerosols and a special device has been suggested by Ivlev 
et al.~(1993).
They produced non-spherical aerosols of NH$_4$Cl with a mean size of 
0.6 $\mu$m and studied the electro-optical response for various 
organic materials adsorbed on the non-spherical particles.

\subsection{Management information}

\subsubsection{Work plan and timetable}

The work on the project is planed to be done within 2 years.

\noi
During the first year it is intended:
\begin{itemize}
\item	to elaborate and test the new SVM code for large sized 
	particles (see Sect.~\ref{theory} above);
\item	to create the new theoretical approach for axisymmetric 
	particles (Sect.~\ref{theory});
\item	to extend the statistical method for incoherent 
	scattering by ensembles of 
	irregularly shaped particles (Sect.~\ref{theory});
\item	to make the database of the optical constants 
	(Sect.~\ref{database});
\item	to interpret the polarimetric observation of stars and 
	to constrain the properties of interstellar dust grains 
	(Sect.~\ref{astro_appl});
\item	to start developing the spheroidal model of atmospheric 
	aerosols (Sect.~\ref{atmos_appl}).
\end{itemize}

\noi
For the second year it is planed:
\begin{itemize}
\item	to elaborate the codes realizing the new approach for 
	axisymmetric particles and the statistical method 
	(Sect.~\ref{theory});
\item	to make a comparative review of the methods for non-spherical 
	particles (Sect.~\ref{theory});
\item	to interpret the polarimetric observation of comets and to 
	draw conclusions on the cometary dust characteristics 
	(Sect.~\ref{astro_appl});
\item	to complete the detailed spheroidal core-mantle model of 
	atmospheric aerosols (Sect.~\ref{atmos_appl});
\item	to develop the scheme of the device for laboratory 
	measurements of extremely low gas admixture concentrations 
	(Sect.~\ref{engee_appl}).
\end{itemize}

\subsubsection{Equipment required}

The main equipment required is hardware for the Russian side.
It is described in detail in the budget (see Sect.~\ref{comm_russ}).

\section{Research fields of the German and Russian sides}

\subsection{Astrophysical Institute and University Observatory Jena}

Interstellar matter plays a key role in the cycle of formation and 
evolution of cosmic matter. 
In Jena, aspects of this cycle are realized in three different 
research topics: Investigation of star-forming regions, research 
dealing with envelopes around late-type stars, and the work related 
to the chemical-mineralogical structure of the interstellar dust 
particles.

The star formation process occurs in optically invisible dark clouds, 
where a complicated interplay of rotation, magnetic fields, turbulence, 
self-gravity, chemical processes, and transport of energy leads to the 
birth of a new star. 
Hence, radio and infrared observations share importance in the study 
of the first years in the lifetime of a star, and in the possible 
creation of new planets in circumstellar disks.

Stellar light is continuously reddened by interstellar dust particles 
and can be used to trace the interstellar dust distribution. 

There is still limited knowledge about the precise shape and size, 
chemical composition and optical properties of the interstellar dust 
particles. 
In order to provide model calculations with realistic data, ``dust 
analogues'' have to be created and measured in the laboratory.

The realistic description of complex scenaria like the formation of a 
new star and planetary systems or the interaction of electromagnetic 
waves with complicated shaped dust particles can be given only 
numerically.
High-performance computers are used to handle the complicated solution 
of differential equations and the simulation of dynamics by applying 
modern algorithms.

In detail, the research topics in Jena are:
\begin{itemize}
\item	theoretical investigation of the evolutionary processes of 
	dust grains such as the growth of molecular mantles and the 
	coagulation of particles;
\item	study of the interaction of electromagnetic radiation with 
	small particles both on a microscopic (light scattering theory) 
	and macroscopic level (multidimensional radiative transfer);
\item	investigation of the influence of the dust population on the 
	dynamics of star-forming regions and of the circumstellar 
	environment of young stellar objects;
\item	experimental investigation of the dust-dust interaction and 
	the growth of solid particles;
\item	laboratory production of cosmic dust analogues and 
	determination of their optical properties by ultraviolet, 
	optical, and infrared spectroscopy.
\end{itemize}

In the last years statistical theories, the discrete dipole 
approximation and the discrete multipole method were developed 
and/or applied to compute the optical behaviour of irregularly 
shaped and inhomogeneous solid particles (Henning \& Stognienko 1993; 
Ossenkopf \& Henning 1994; Stognienko et al.~1995; Michel 1995; 
Henning \& Stognienko 1996; Michel et al.~1996).

A large body of the research was done within the Max Planck Society 
Research Unit ``Dust in Star-forming Regions'' at the University Jena 
during the last 5 years.
This group is presently incorporated in the Astrophysical Institute 
and University Observatory Jena.

For a more complete overview about the recent activities (with 
references), we refer to the annual report prepared for the 
``Mitteilungen der Astronomischen Gesellschaft'' (attached 
document).

\ms
The recently finished or running grants of the participants from the 
German side are as follows:
\begin{tabbing}
Principal Investigator: \= \kill
Principal Investigator: \> Th.\ Henning/P.\ Bussemer \\
Support: 		\> Past \\
Proposal title: 	\> Untersuchung zu optischen Eigenschaften \\
			\> inhomogener Medien mit Anwendung \\
			\> auf kosmische Staubteilchen \\
Source of support:	\> Deutsche Forschungsgemeinschaft \\
Total award amount:	\> 8.700 DM for travel and material expenses,\\
			\> 18.200 DM for equipment, \\
			\> 1 BAT-O IIa position \\
Period covered:		\> 1992--1995 \\
Location of research:	\> Astrophysical Institute and University 
			   Observatory \\
			\> Jena, Institute for Solid State Theory and \\
			\> Theoretical Optics Jena \\
\\
Principal Investigator: \> Th.\ Henning \\
Support: 		\> Past \\
Proposal title: 	\> Experiment zur Aggregation kosmischen 
			   Staubes \\
			\> [CODAG] \\
Source of support:	\> DARA GmbH \\
Total award amount:	\> 113.500 DM for travel and material 
			   expenses,\\
			\> 916.400 DM for equipment and sub-contracts,\\
			\> 2 BAT-O IIa/2 positions \\
Period covered:		\> 1993--1996 \\
Location of research:	\> Astrophysical Institute and University 
			   Observatory \\
			\> Jena \\
\\ \\
Principal Investigator: \> M.\ Mutschke/J.\ Dorschner \\
Support: 		\> Current \\
Proposal title: 	\> Matrixisolationspektroskopie 
			   nichtagglomerierter \\
			\> Teilchen \\
Source of support:	\> Deutsche Forschungsgemeinschaft \\
Total award amount:	\> 12.500 DM for travel and material expenses,\\
			\> 1 BAT-O IIa/2 position \\
Period covered:		\> 1994--1997 \\
Location of research:	\> Astrophysical Institute and University 
			   Observatory \\
			\> Jena \\
\\
Principal Investigator: \> Th.\ Henning/W.\ Pfau \\
Support: 		\> Current \\
Proposal title: 	\> ISO-Beobachtungen der zirkumstellaren 
			   Materie \\
			\> um sehr junge und massenreiche Sterne \\
Source of support:	\> BMFT Verbundforschung Astronomie/Astrophysik \\
Total award amount:	\> 50.500 DM for travel and material expenses,\\
			\> 1 BAT-O IIa position (3 years), \\
			\> 1 BAT-O IIa/2 position (3 years)\\
Period covered:		\> 1994--1999 \\
Location of research:	\> Astrophysical Institute and University 
			   Observatory \\
			\> Jena \\
\\
Principal Investigator: \> Th.\ Henning \\
Support: 		\> Current \\
Proposal title: 	\> Mikrophysikalische Staubentwicklungsprozesse \\
			\> beim protostellaren Kollaps \\
Source of support:	\> Deutsche Forschungsgemeinschaft \\
Total award amount:	\> 11.500 DM for travel and material expenses,\\
			\> 1 BAT-O IIa/2 position \\
Period covered:		\> 1995--1997 \\
Location of research:	\> Astrophysical Institute and University 
			   Observatory \\
			\> Jena \\
\\
Principal Investigator: \> Th.\ Henning/U.\ Kreibig \\
Support: 		\> Current \\
Proposal title: 	\> Untersuchung der optischen Eigenschaften 
			   von \\
			\> Teilchen aus vorwiegend amorphem 
			   Kohlenstoff \\
Source of support:	\> Deutsche Forschungsgemeinschaft \\
Total award amount:	\> 26.500 DM for travel and material expenses,\\
			\> 1 BAT-O IIa position \\
Period covered:		\> 1996--1998 \\
Location of research:	\> Astrophysical Institute and University 
			   Observatory \\
			\> Jena, RWTH Aachen \\
\\ \\
Principal Investigator: \> Th.\ Henning/H.W.\ Yorke \\
Support: 		\> Current \\
Proposal title: 	\> Staubwachstum in protostellaren \\
			\> Akkretionsscheiben \\
Source of support:	\> Deutsche Forschungsgemeinschaft \\
Total award amount:	\> 5.500 DM for travel and material expenses,\\
			\> 1 BAT-O IIa/2 position \\
Period covered:		\> 1996--1997 \\
Location of research:	\> Astrophysical Institute and University 
			   Observatory \\
			\> Jena, Institute for Astronomy and \\
			\> Astrophysics W{\"u}rzburg
\end{tabbing}

\ms
The curriculum vitae and the publication list of the German scientists
taking part in the project are presented as attached document.

\subsection{Astronomical Institute of the St.~Petersburg University}

The most important results obtained in the institute in the last 
half-century are connected with the radiation transfer theory and 
the polarimetric observations.
The directions were founded by V.A.~Ambartsumyan, 
V.V.~Sobolev, and V.A.~Dombrovsky who gave 
the origin to the scientific school that has continued 
its work till now.

The group of researchers studying the physics of interstellar 
matter have the following main directions of work:
simulations of radiation transfer and interaction of radiation 
with dust particles and applications of this theoretical basis 
to astrophysical observations including those of polarization.

The main research topics of the group in the last years have been 
as follows:
\begin{itemize}
\item	Monte Carlo simulations of polarized radiation transfer 
	in astrophysical objects (Voshchinnikov \& Karjukin 1994; 
	Voshchinnikov et al.~1995; Krivova et al.~1996a);

\item	development of the light scattering theory for homogeneous 
	and coated spheroidal particles (Voshchinnikov \& Farafonov 
	1993, 1994, 1996;
% Farafonov 1994a,b;
	Farafonov et al.~1996; Voshchinnikov 1996; Farafonov \& 
	Voshchinnikov 1996; Hovenier et al.~1996);

\item	modelling of extinction and polarization produced by 
	interstellar dust grains (Voshchinnikov \& Il'in 1993; 
	Il'in et al.~1994; Il'in \& Henning 1996; Somsikov~1996);

\item	study of circumstellar dust shells, including the effects 
	of grain dynamics, scattered light and polarization, gas 
	ionization balance and the interpretation of observations  
	(Il'in \&  Voshchinnikov 1993; Il'in 1994; Kholtygin et 
	al.~1995; Voshchinnikov et al.~1995, 1996; Krivova 1996; 
	Th\'e et al.~1996).
\end{itemize}

A part of the work was executed in collaboration with scientists 
from the Laboratory of Statistical Modelling of the St.~Petersburg 
University (V.V.~Karjukin), the Crimea Astrophysical Observatory 
(V.P. Grinin), the Astrophysical Institute and the Max Planck 
Society Research Unit at the University Jena (Th.~Henning, 
R.~Stognienko, O.~Fischer, A.B.~Menshchikov), the Astronomical 
Institute of the University Amsterdam (P.S.~Th\'e, F.~Molster, 
M.E.~van den Ancker), the Free University Amsterdam 
(J.W.~Hovenier) and others.

The longtime contacts with the group of experts in atmospheric 
physics from the Physical Institute of the St.~Petersburg 
University (L.S.~Ivlev, O.M.~Korostina and others) have 
resulted, for example, in the development of the spheroidal 
model of atmospheric aerosol particles (Voshchinnikov \& 
Farafonov 1994).

In particular fruitful was the joint work on the light scattering 
theory with the group from the St.~Petersburg Academy of Aerocosmic 
Instrumentation (V.G.~Farafonov and his collaborators).
It has lasted over 10 years and resulted in about 30 papers published 
in different scientific journals and presented at many conferences 
(see the references given in Voshchinnikov \& Farafonov 1993 and in 
Sect.~\ref{past_contacts}).

Because of these direct contacts with the other research groups 
(from the St.~Petersburg Academy of Aerocosmic Instrumentation 
and from the Physical Institute of the St.~Petersburg University), 
the Astronomical Institute of the St.~Petersburg University 
was selected to be the base institute of the project and 
N.V.~Voshchinnikov to be the project coordinator from the 
Russian side.

\ms
The recently finished or running grants of the participants from the 
Russian side are as follows:
\begin{tabbing}
Principal Investigator: \= \kill
Principal Investigator:	\> N.V.~Voshchinnikov \\
Support: 		\> Past \\
Proposal title: 	\> Gas and dust around Herbig Ae/Be stars \\
Source of support:	\> European Southern Observatory (ESO C{\&}EE \\
			\> Programme) \\
Total award amount:	\> 4.500 DM for 6 researchers and equipment \\
Period covered:		\> 1993--1995 \\
Location of research:	\> Astronomical Institute of St.~Petersburg 
			   University \\
\\
Principal Investigator:	\> N.V.~Voshchinnikov \\
Support:		\> Past \\
Proposal title:		\> Core-mantle spheroidal model of 
			   interstellar and \\
			\> interplanetary dust grains \\
Source of support:	\> International Science Foundation \\
Total award amount:	\> 9.000 \$ for 4 researchers and equipment \\
Period covered:		\> 1994--1995 \\
Location of research:	\> Astronomical Institute of St.~Petersburg 
			   University \\
\\ \\
Principal Investigator:	\> N.V.~Voshchinnikov \\
Support:		\> Current \\
Proposal title:		\> Dynamics of circumstellar and interplanetary \\
			\> dust grains \\
Source of support:	\> Russian Committee of High Education\\
Total award amount:	\> 5.000.000 rubles (about 1.000 \$) in 1996 \\
			\> for 3 researchers and equipment \\
Period covered:		\> 1996--1997 \\
Location of research:	\> Astronomical Institute of St.~Petersburg 
			   University \\
\\
Principal Investigator:	\> V.G.~Farafonov \\
Support:		\> Current \\
Proposal title:		\> Theoretical problems of the interaction of \\
			\> the electromagnetic radiation with disperse \\
			\> systems having complex microstructure \\
Source of support:	\> Russian Committee of High Education \\
Total award amount:	\> 5.000.000 rubles (about 1.000 \$) in 1996 \\
			\> for 3 researchers and equipment \\
Period covered:		\> 1996--1997 \\
Location of Research:	\> St. Petersburg State Academy of Aerocosmic \\
			\> Instrumentation
\end{tabbing}

\ms
The curriculum vitae and the publication list of the Russian scientists
taking part in the project are presented as attached document.

\section{Past contacts between the German and Russian sides}\label{past_contacts}

In 1992 a co-operation between the Max Planck Society Research Unit 
``Dust in Star-forming Regions'' at the University Jena and the 
Astronomical Institute of the St.~Petersburg University (AI SPbU) 
has been started in the field of light scattering by small particles.
Several short and long term stays allowed the elaboration of results 
on different topics in that field.

V.B.~Il'in (research associate of AI SPbU) worked in Jena during 6 
months as a fellow of the Max Planck Society.
Research subject were the dynamics of non-spherical circumstellar 
grains (Il'in 1994; Il'in \& Krivov 1994).

Supported by the Max Planck Society, N.V.~Voshchinnikov (leading 
research associate of AI SPbU) stayed for 6 months in Jena working 
on a Monte Carlo code and on the modelling of the circumstellar 
dust shells (Voshchinnikov 1994; Voshchinnikov \& Karjukin 1994; 
Voshchinnikov et al.~1994a; Kholtygin et al.~1994; Voshchinnikov 
et al.~1995).
Problems of light scattering by non-spherical particles were also 
considered (Voshchinnikov et al.~1994b).

O.~Fischer visited St.~Petersburg for two weeks in 1994 and discussed 
the mathematical problems of the Monte Carlo technique with V.V.\ 
Karjukin and the problems of light scattering by spheroidal particles 
with N.V.~Voshchinnikov.

In 1994 V.V.~Somsikov attended the annual meeting of the Research Unit 
and during an one week stay in Jena computational aspects of light 
scattering by inhomogeneous non-spherical particles were discussed.

During the stay of V.B.~Il'in (1995/1996, supported by the Alexander 
von Humboldt Foundation) an unified model for the explanation of the interstellar polarization and extinction were developed (Il'in \& 
Henning 1996).
V.B.~Il'in and N.A.~Krivova from St.~Petersburg together with 
O.~Fischer, A.~Menshchikov, and B.~Stecklum from Jena used 
modified radiative transfer codes to interprete new observations 
of dusty shells surrounding young stars (Krivova \& Il'in 1996; 
Il'in et al.~1996b; Krivova et al.~1996a, 1996b).
First observations with the new camera TAUMOK of the Tautenburg 
Observatory and spectral classification of stars in a Bok globule 
were performed by Il'in et al.~(1996a) with help of Th.~Lehmann 
and R.~Launhardt from the University Observatory Jena.
See also the papers by Kholtygin et al.\ (1995), Il'in et al.\ 
(1996c), and Il'in \& Voshchinnikov (1996) for other topics of 
the work by V.B.~Il'in and collaborators from Jena.

\section{State of the project}

This proposal is not part of any other tightly related project and is 
submitted to the Volkswagen-Stiftung only.

\section{Budget}

\begin{tabular}{|l|r|r|r|}
\multicolumn{4}{l}{\large\bf German side}\\
\hline\hline
\multicolumn{1}{|l|}{ \ \ \ item} & 
\multicolumn{1}{c|}{first year} &
\multicolumn{1}{c|}{second year} & 
\multicolumn{1}{c|}{total}\\
\hline
%
{\bf Regular expenses}        &           &           &            \\
%
\#1. Project head's trips     &           &           &            \\
~~~~~~~to St.~Petersburg      &           &           &            \\
\W1.1 Travel expenses         &  2.642 DM &  2.642 DM &   5.284 DM \\
\W1.2 Accommodation           &  3.240 DM &  3.240 DM &   6.480 DM \\
%
\#2. Other participants' trips&           &           &            \\
~~~~~~~to St.~Petersburg      &           &           &            \\
\W2.1 Travel expenses         &  2.514 DM &  2.514 DM &   5.028 DM \\
\W2.2 Accommodation           &  3.920 DM &  3.920 DM &   7.840 DM \\
%
\#3. Material                 &  3.000 DM &  3.000 DM &   6.000 DM \\
\hline
{\bf Total}                   & 15.316 DM & 15.316 DM &  30.632 DM \\
\hline
\hline
\multicolumn{4}{l}{}\\
\multicolumn{4}{l}{\large\bf Russian side}\\
\hline\hline
\multicolumn{1}{|l|}{ \ \ \ item} & 
\multicolumn{1}{c|}{first year} &
\multicolumn{1}{c|}{second year} & 
\multicolumn{1}{c|}{total}\\
\hline
%
{\bf Regular expenses}        &           &           &            \\
%
\#4. Trips to Jena            &           &           &            \\
\W4.1 Travel expenses         &  3.940 DM &  3.940 DM &   7.880 DM \\
\W4.2 Accommodation           & 31.400 DM & 31.400 DM &  62.800 DM \\
%
\#5. Material                 &    800 DM &    800 DM &   1.600 DM \\
%
{\bf Additional expenses}     &           &           &            \\
%
\#6. Equipment                &  8.000 DM &  3.200 DM &  11.200 DM \\
%
\#7. Software Contracts       &  9.000 DM &  3.000 DM &  12.000 DM \\
%
\#8. Literature (books)       &  1.500 DM &    500 DM &   2.000 DM \\
%
\#9. Joint workshop           &      0 DM & 22.000 DM &  22.000 DM \\
\hline
{\bf Total}                   & 53.640 DM & 63.840 DM & 117.480 DM \\
\hline
\hline
\multicolumn{4}{l}{}\\
\hline\hline
{\bf Total for both sides}    & 68.956 DM & 79.156 DM & 148.112 DM \\
\hline
\hline
\end{tabular}

\subsection{Comments on the German side's budget}

{\bf Regular expenses}

\ms
{\bf \#1. Project head's trips to St.~Petersburg}

\noi
The project includes several connected tasks in light scattering 
theory, laboratory data analysis, astrophysics, atmosphere optics 
(see Sect.~\ref{goals}).
To solve the tasks the experience of different scientific groups 
is required and will be used. 
About 15 scientists (mainly in Russia) will participate in the work.
It is obvious that for a successful management of the project its head 
(from the German side) must have the possibility periodically to visit 
St.~Petersburg and to contact the Russian participants.
Otherwise it will be impossible to coordinate the work of the Russian 
and German sides.

\noi
Two 6 days trips per year of the project head to St.~Petersburg are 
planed: 
\newpage
{\small\smallskip
\noi
 -- Railway: Jena--Berlin--Jena (1. class, 2 $\times$ 202 DM)
                                                      \dotfill   404 DM

\noi
 -- Lufthansa flight: Berlin--St.~Petersburg--Berlin 
                                 (2 $\times$ 1119 DM) \dotfill 2.238 DM
							%      2.642 DM

\noi
 -- Subsistence allowance (2 $\times$ 90 DM $\times$ 6 days)
                                                      \dotfill 1.080 DM

\noi
 -- Single hotel room (2 $\times$ 180 DM $\times$ 6 days)
                                                      \dotfill 2.160 DM
							%      3.240 DM

}

\ms
{\bf \#2. Other participants' trips to St.~Petersburg}

\noi
For the visits of German collaborators to St.~Petersburg 2 trips, 
each about 2 weeks, are planed per year:

{\small\smallskip
\noi
 -- Railway: Jena--Berlin--Jena (2 $\times$ 138 DM)   \dotfill   276 DM

\noi
 -- Lufthansa flight: Berlin--St.~Petersburg--Berlin 
                                 (2 $\times$ 1119 DM) \dotfill 2.238 DM
							%      2.514 DM

\noi
 -- Subsistence allowance (2 $\times$ 90 DM $\times$ 14 days)
                                                      \dotfill 2.520 DM

\noi
 -- Single room/flat in the St.~Petersburg University hotel

   (2 $\times$ 50 DM $\times$ 14 days)                \dotfill 1.400 DM
							%      3.920 DM

}

\ms
{\bf \#3. Material}

\noi
These expenses will be directed to support the planed visits and work 
of Russian participants in Jena (see comments to item \#4 below).

\subsection{Comments on the Russian side's budget}\label{comm_russ}

{\bf Regular expenses}

\ms
{\bf \#4. Trips to Jena}

\noi
There are 5 trips (2 $\times$ 2 weeks and 3 $\times$ 3 months) per year of Russian scientists planed:

{\small\smallskip
\noi
 -- Railway: Berlin--Jena--Berlin (5 $\times$ 138 DM)
                                                    \dotfill     690 DM

\noi
 -- Aeroflot flight: St.~Petersburg--Berlin--St.~Petersburg 
                                (5 $\times$ 650 DM) \dotfill   3.250 DM
							%      3.940 DM

\noi
 -- Accommodation (2 $\times$ 2 weeks)              \dotfill   3.500 DM

\noi
 -- Accommodation (3 $\times$ 3 months)             \dotfill  27.900 DM
							%     31.400 DM

}

\ms
{\bf \#5. Material}

\noi
Because of low funds of the Russian scientific institutes, 
cartridges for a laser printer and a copy machine are planed 
to be purchased.

\bs
{\bf Additional expenses}

\ms
{\bf \#6. Equipment}

\noi
The main part of the project is the creation of new numerical 
techniques in light scattering theory (see Sect.~\ref{theory}) 
and their wide-field applications (see 
Sect.~\ref{astro_appl}--\ref{atmos_appl}).
The main place of the planed creation and development of the software 
will be St.~Petersburg.
The best available computer for the Russian participants is an IBM 
PC AT~486/50~MHz with the 16~MB memory.
To create the software at the current level and to be able to make 
extensive test calculations, a faster computer with a larger memory 
(more than about 64~MB) is needed.
Therefore, during the first year of the project it is intended to buy 
an appropriate PC.

\noi
The database of optical constants created in the project should be 
widely distributed not only via anonymous FTP and the World Wide Web 
but also on CD-ROM.
For that purpose a CD-ROM recorder and about 100 CD-ROM records will 
be needed in the second year of the project.
It is intended to buy a configuration similar to the following 
(equipment and prices taken from ``c't magazin f{\"u}r computer 
technik'', 11/96):

{\small\smallskip
\noi
 -- Intel Pentium Pro 166 MHz computer with 64 MB memory, 

 2 GB SCSI harddisk, monitor, printer \dotfill 8.000~DM

\noi
 -- CD-ROM recorder (Yamaha CDR 100), writer-software (WinOnCD 3.0), 

 100 CD-ROM records (Phillips)        \dotfill 3.200~DM

}

\ms
{\bf \#7. Software Contracts}

\noi
The additional expenses are connected with the necessity to create 
quickly a good software.
Some key subroutines of the codes and of the database to be developed 
(see Sect.~\ref{theory}--\ref{database}) determine the efficiency of 
the software.
Therefore, they should be developed by professional programers (from 
Russia).
The contribution of these experts is also of large importance at the 
early stages of any software creation.

\ms
{\bf \#8. Literature}

\noi
A special problem is the absence of new books on the subject of the 
project in the scientific libraries of St.~Petersburg.
Practically, neither the libraries nor the institutes have had money 
to buy books on the dust related topics for about the last 5 years.
So, several modern books on the subject have to be purchased.

\ms
{\bf \#9. Joint workshop}

\noi
An international meeting devoted to the actual problems of science 
will have a very large impact on the scientific community in Russia.
For understandable reasons, only a few both national and international 
scientific meetings occurred in Russia in the last years.
Now, the economical situation in the country is stabilizing and for 
the first time after the ``perestroika's'' begin it becomes possible 
to fulfil and guarantee the conditions (quality of service, hotels, 
equipment, etc.) necessary for such an event to be organized well.
Moreover, at present the expenses in Russia are a bit lower than 
those of a similar service in many other european countries.

\noi
For these reasons, it is suggested to hold in St.~Petersburg an 
international workshop whose topics would be in the mainstream 
of the scientific interests of the German and Russian sides 
(see the attached document for a possible program of the 
workshop).

\noi
It is planed to hold a 4 days meeting at the Pulkovo Observatory, 
St.~Petersburg, with accommodation partly in the Pulkovo Observatory 
hotel and partly in a four-stars hotel on the way to the Observatory 
from the city center.
The large conference hall, scientific library and some hardware 
(copy machines, overheads, PC's with an Internet connection, etc.) 
will be available by courtesy of the Pulkovo Observatory.

\noi
It should be noted that provided the financial support from the 
Russian Foundation for Basic Research and the permission of the 
International Astronomical Union (IAU) will be given, the workshop 
will be extended to an IAU Colloquium that will have a bit more wide 
topics and involve more experts in the field.

%{\small\smallskip
%{\bf Components of the sums in item \#9:}
%
%\noi
% -- Running expenses (conference hall cleaning, materials, etc.)
%                                                    \dotfill    500 DM
%
%\noi
% -- Accommodation of 10 persons in the Pulkovo Observatory hotel for 4 nights
%
%        (40 DM per night)                           \dotfill  1.600 DM
%
%\noi
% -- Accommodation of 5 persons in a hotel for 4 nights
%
%        (180 DM per night)                          \dotfill  3.600 DM
%
%\noi
% -- Cultural program
%                                                    \dotfill    750 DM
%
%\noi
% -- Support of some participants (travels and subsistence allowance),
%
%        additional expenses
%                                                    \dotfill 13.550 DM
%}

\newpage
\section*{References to the participants' papers\footnote{References
to other papers are given in the text}}
\addcontentsline{toc}{section}{References}
\label{Ref_start}

\small
\bitem { Andreev S.D., Ivlev L.S. (1995a)
%}{ Simulation of optical characteristics of atmospheric ground layer aerosol
% within 0.3--15 mkm spectral range. I. Principles of constructing of the model.}{
 \OpAtO {\bf 8}, 788--795.}

\bitem { Andreev S.D., Ivlev L.S. (1995b)
%}{ Simulation of optical characteristics of atmospheric ground layer aerosol
% within 0.3--15 mkm spectral range. II. Model of aerosol content
% and structure.}{
 \OpAtO {\bf 8}, 1227--1235.}

\bitem { Andreev S.D., Ivlev L.S., Mikhailov E.F., Kiselev A.A. (1995)
%}{ Optical characteristics of smoke particles.}{
 \OpAtO {\bf 8}, 687--692.}

\bitem { Begemann B., Dorschner J., Henning Th., Mutschke H., Thamm E. (1994)
%}{ A laboratory approach to the interstellar sulfide dust problem. }{
 \ApJL {\bf 423}, L71--L74.}

\bitem { Begemann B., Henning Th., Mutschke H., Dorschner J. (1995)
%}{ Mg/Fe oxides - astrophysical origin and optical constants. }{
 \PlSpSc {\bf 43}, 1257--1261.}

\bitem { Begemann B., Dorschner J., Henning Th., Mutschke H.,
 G{\"u}rtler J., K{\"o}mpe C., Nass R. (1996a)
%}{ Optical properties of amorphous aluminum oxide grains. }{
 \ApJ submitted.}

\bitem { Begemann B., Henning Th., Mutschke H., Dorschner J. (1996b)
%}{ Optical properties of glassy SiS$_2$ and the 21 micron feature. }{
 \ApJL {\bf 464}, L195--L198.}

\bitem { Blum J., Henning Th., Ossenkopf V., Sablotny R., Stognienko R,
 Thamm E.  (1994)
%}{ Fractal growth and optical behaviour of cosmic dust. }{
 In: Novak M.M. (ed.)
 Fractals in the Natural and Applied Sciences.
 Elsevier, North-Holland, pp.47--59.}

%\bitem { Dorschner, J., Henning, Th. (1995)
%}{ Dust Metamorphosis in the Galaxy. }{
% \AApRev {\bf 6}, 271-333.}

\bitem { Dorschner J., Begemann B., Henning Th., J{\"a}ger C., Mutschke H. (1995)
%}{ Steps toward interstellar silicate mineralogy.
% II. Study of Mg-Fe-silicate glasses of variable composition. }{
 \AAp {\bf 300}, 503--520.}

\bitem { Farafonov V.G. (1983)
%}{ Diffraction of the plane electromagnetic
% wave on the dielectric spheroid. }{
 Differential Equations (Sov.) {\bf 19}, 1765--1773.}

\bitem { Farafonov V.G. (1994a)
%}{ Scattering of electromagnetic radiation by two-layer spheroids. }{
 \OpSp {\bf 76}, 87--91.}
%% (English translation in Opt. Spectr. V.76. P.79--83.)}

\bitem { Farafonov V.G. (1994b)
%}{ Light scattering by spheroidal particles in quasistatic approximation.}{
 \OpSp {\bf 77}, 455--458.}

\bitem { Farafonov V.G., Voshchinnikov N.V. (1996)
%}{ Absorption of radiation by core-mantle spheroidal particles. }{
 \OpSp accepted.}

\bitem { Farafonov V.G., Voshchinnikov N.V.,  Somsikov V.V. (1996)
%}{ Light scattering by a core-mantle spheroidal particle. }{
 \ApplOpt accepted.}

\bitem { Gavrilova L.A., Ivlev L.S. (1991)
%}{ The effect of choice between aerosol models on the calculations of
%  atmospheric radiation characteristics. }{
 \OpAtO {\bf 4}, 927--930.}
%% (English translation in \AtOp {\bf 4}, 650--652.)

\bitem { Gavrilova L.S., Ivlev L.S. (1995)
%}{ Aerosols models for calculations of radiative characteristics of the
% atmosphere.}{
 \IzvFAO {\bf 31}, 667--678.}

\bitem { Gavrilova L.S., Ivlev L.S. (1996)
%}{ Parameterization of the global aerosol models for
%a computation of radiative characteristics of the atmosphere.}{
 \IzvFAO {\bf 32}, 172--182.}

\bitem { Henning Th., Stognienko R. (1993)
%}{ Porous grains and polarization of light: the silicate features. }{
 \AAp {\bf 280}, 609--616.}

\bitem { Henning Th., Stognienko R. (1996)
%}{ Dust opacities for protoplanetary accretion disks---influence
% of dust aggregates. }{
 \AAp {\bf 311}, 291--304.}

\bitem { Henning Th., Begemann B., Mutschke H., Dorschner J. (1995a)
%}{ Optical properties of oxide dust grains. }{
 \AApS {\bf 112}, 143--149.}

\bitem { Henning Th., Michel B., Stognienko R. (1995b)
%}{ Dust opacities in dense regions. }{
 \PlSpSc {\bf 43}, 1333--1343.}

\bitem { Hovenier J.W., Lumme K., Mishchenko M.I.,
 Voshchinnikov N.V., Mackowski D.W., Rahola J. (1996)
%}{ Computations of scattering matrices of four types
% of non-spherical particles using diverse methods. }{
 \JQSRT accepted.}

\bitem { Il'in V.B. (1994)
%}{ Small non-spherical dust grains in envelopes of M giants. }{
 \AAp {\bf 281}, 486--490.}

\bitem { Il'in  V.B., Henning Th. (1996)
%}{ Modeling of interstellar extinction and polarization with
% spheroidal particles. }{
 \AAp in preparation.}

\bitem { Il'in V.B., Krivov A.V. (1994)
%}{ Dynamics of small grains near Herbig Ae stars. }{
 In: Th\'e P.S. et al.~(eds.)
 The Nature and Evolutionary Status of Herbig Ae/Be Stars.
 \ASPcs {\bf 62}, 177--180.}

\bitem { Il'in V.B., Voshchinnikov N.V. (1993)
%}{ The dust grains motion in envelopes of Herbig Ae stars. }{
%  \AZh {\bf 70}, 721--730.}
%%  (English translation in Sov. Astron. J.).
 \ARep {\bf 37}, 362--367.}

\bitem { Il'in V.B., Voshchinnikov N.V. (1996)
%}{ Radiation pressure on non-spherical dust grains in envelopes of
% late-type giants. }{
 \AAp in preparation.}

\bitem { Il'in V.B., Khudyakova T.N., Reshetnikov V.P. (1994)
%}{ Polarization of starlight by dust in Bok globule B5. }{
% \AZh {\bf 71}, 245--249.}
%%   (English translation in
 \ARep {\bf 38}, 214--218.}

\bitem { Il'in V.B., Khoudiakova T.N., Ziener R., Ball M. (1996a)
%}{ Spectral classification of stars in the region of the Bok globule B5
%  using spectra obtained with TAUMOK. }{
 \AAp in preparation.}

\bitem { Il'in  V.B., Krivova N.A., Menshchikov A.B. (1996b)
%}{ Modelling of the IR intensity maps for HAeBe stars with Algol-like minima. }{
 In: The Role of Dust in the Formation of Stars.
 \LectNPh in press.}

\bitem { Il'in V.B., Stognienko R., Voshchinnikov N.V. (1996c)
%}{ Spheroidal particles as a tool for comparison of different solutions of
%  light scattering problem. }{
 \JQSRT in preparation.}

\bitem { Ivlev L.S. (1982)
%}{ The chemical composition and structure of atmospheric aerosols. }{
   Leningrad Univ. Press, Leningrad, 366p.}

\bitem { Ivlev L.S., Andreev S.D. (1986)
%}{ The optical properties of atmospheric aerosols. }{
   Leningrad Univ. Press, Leningrad, 359p.}

\bitem { Ivlev L.S., Korostina O.M. (1994)
%}{ Computation of optical characteristics for stratospheric aerosol particles
% with two-layered structure. }{
 \IzvFAO {\bf 30},  802--806.}

\bitem { Ivlev L.S., Sushko B.K., Bahtizin R.S. (1993)
%}{ Electrooptical properties of the chloride ammonia aerosols. }{
 \OpAtO {\bf 6},  496--502.}
%% (English translation in \AtOp {\bf ?}, ??.)

\bitem { J{\"a}ger C., Mutschke H., Begemann B., Dorschner J., Henning Th.,
 (1994)
%}{ Steps toward interstellar silicate mineralogy.
% I. Laboratory results of a silicate glass of mean cosmic composition. }{
 \AAp {\bf 292}, 641--655.}

\bitem { Kholtygin A.F., Il'in  V.B., Voshchinnikov N.V. (1994)
%}{ Ionization structure of the shells around Herbig Ae/Be stars. }{
 In: Th\'e P.S. et al.~(eds.)
 The Nature and Evolutionary Status of Herbig Ae/Be Stars.
 \ASPcs {\bf 62}, 197--198.}

\bitem { Kholtygin A.F., Il'in V.B., Voshchinnikov N.V. (1995)
%}{ Ionization structure of the shells surrounding Herbig Ae/Be stars. }{
 \AAp submitted.}

\bitem { Kondratyev K.Ya., Ivlev L.S., Korostina O.M. (1992)
%}{ Optical characteristics of the complicate content cloudless perticles.}{
 \DAN {\bf 326}, 617--621.}

\bitem { Kondratyev K.Ya., Ivlev L.S. et al.~(1993)
%}{ Relation between variations of the nearground ozone and aerosol.}{
 \DAN {\bf 341}, 287--289.}

\bitem { Kondratyev K.,Ya., Ivlev L.S., Galindo I. (1995)
%}{ Application of the factors enrichments for investigation of the volcanic
% explosion products.}{
 \DAN {\bf 345}, 111--113.}

\bitem { Krivova N.A. (1996)
%}{ Herbig Ae stars with Algol-like minima: modelling of the spectral energy
% distribution and colour behaviour during the minima. }{
 \SovAL submitted.}

\bitem { Krivova N.A., Il'in V.B. (1996)
%}{ Multi-wavelength study of HAeBe  stars with Algol-like minima. }{
 In: The Role of Dust in the Formation of Stars.
 \LectNPh in press.}

\bitem { Krivova N.A., Il'in V.B., Fischer O. (1996a)
%}{ Dust around Herbig Ae stars: additional constraints from
%  their photometric and polarimetric variability. }{
  In: From Stardust to Planetesimals.
  \NASAp in press.}

\bitem { Krivova N.A., Il'in V.B., Fischer O., Stecklum B. (1996b)
%}{ Herbig Ae stars with Algol-like minima:
%  modelling of polarimetric observations of CQ Tau. }{
  \SovAL in preparation.}

\bitem { Michel B. (1995)
%}{ Statistical method to calculate extinction by small irregularly
% shaped particles. }{
 \JOSA {\bf A12}, 2471--2481.}

\bitem { Michel B., Lakhtakia A. (1995)
%}{ Strong property fluctuations theory for homogenizing chiral particulate
% composites. }{
 \PhRev {\bf E51}, 5701--5707.}

\bitem { Michel B., Lakhtakia A. (1996)
%}{ On the application of the strong property fluctuation theory for
% homogenizing chiral particulate composites. }{
 \JPhD {\bf 29}, 1431--1440.}

\bitem { Michel B., Henning Th., Stognienko R., Rouleau F. (1996)
%}{ Extinction properties of dust grains: a new computational technique. }{
 \ApJ {\bf 468}, 434--441.}

\bitem { Mutschke H., Dorschner J., Henning Th., J{\"a}ger C., Ott U. (1995)
%}{ Facts and artifacts in interstellar diamond spectra. }{
 \ApJL {\bf 454}, L157--L160.}

\bitem { Ossenkopf V., Henning Th. (1994)
%}{ Dust opacities for protostellar cores. }{
 \AAp {\bf 291}, 943--959.}

%\bitem { Pueschel R.F., Ivlev L.S. (1991)
%}{ Anthropogenic aerosol. }{
% In: Kondratyev K.Ya.~(ed.). Aerosol and Climate.
% Gidrometeoizdat, Leningrad, pp.191--251}

\bitem { Somsikov V.V. (1996)
%}{ Optical properties of core-mantle spheroidal grains  }{
 \SovAL in press.}

\bitem { Stognienko R., Henning Th., Ossenkopf V. (1995)
%}{ Optical properties of coagulated particles. }{
 \AAp {\bf 296}, 797--809.}

\bitem { Th\'{e} P.S., P\'{e}rez M.R., Voshchinnikov N.V., van den Ancker M.E.
 (1996)
%}{ The variable Herbig Ae star HR 5999: XII. Its circumstellar extinction law. }{
 \AAp accepted.}

\bitem { Vasilyev O.B., Willmann Ch.J., Ivlev L.S. et al.~(1989)
%}{  On the nature of noctilucent clouds. }{
 In: Collection of works of the international workshop of Noctilucent Clouds.
 Valgus, Tallinn, pp.123--133.}

\bitem { Voshchinnikov N.V. (1989)
%}{ Determination of dust properties and magnetic fields from polarimetric and
% photometric observations of stars. }{
 \AN {\bf 310}, 265--271.}

\bitem { Voshchinnikov N.V. (1990a)
%}{ Radiation pressure on spheroidal particles. }{
 \ARep {\bf 34}, 429--432.}

\bitem { Voshchinnikov N.V. (1990b)
%}{ Optical properties of spheroidal dust particles.
% Forward transmitted radiation. }{
 \ARep {\bf 34}, 535--541.}

\bitem { Voshchinnikov N.V. (1990c)
%}{ Interstellar  feature $\lambda$ 2200A and non-spherical graphite grains. }{
 \SovAL {bf 16}, 215--219.}

\bitem { Voshchinnikov N.V. (1994)
%}{ Models of dust shells around Herbig Ae stars. }{
  In: Th\'e P.S. et al.~(eds.)
  The Nature and Evolutionary Status of Herbig Ae/Be Stars.
%  Astron. Soc. Pasif. Conf. Ser., {\bf 62}, 167--170.}
  \ASPcs {\bf 62}, 167--170.}

\bitem { Voshchinnikov N.V. (1996)
%}{ Electromagnetic scattering  by homogeneous and coated spheroids:
% calculations using the separation of variables method. }{
 \JQSRT in press.}

\bitem { Voshchinnikov N.V., Farafonov V.G. (1993)
%}{ Optical  properties  of spheroidal particles. }{
 \ApSpSc {\bf 204}, 19--85.}

\bitem { Voshchinnikov N.V., Farafonov V.G. (1994)
%}{ Peculiarities of radiation
% scattering by nonspherical particles of atmospheric aerosols. }{
 \IzvFAO {\bf 30}, 46--52.}

\bitem { Voshchinnikov N.V., Farafonov V.G. (1996)
%}{ On the calculations of the prolate spheroidal wavefunctions of large and
% complex argument. }{
 Computer Phys.~Commun., in preparation.}

\bitem { Voshchinnikov N.V., Il'in V.B. (1987)
%}{ On the determination of the interstellar extinction from the colour excess. }{
 \SovAL {\bf 13}, 157--160.}

\bitem { Voshchinnikov N.V., Il'in V.B. (1993)
%}{ Interstellar extinction curve in the far and extreme ultraviolet. }{
% \AZh {\bf 70}, 38--46.}
%% English translation in
 \ARep {\bf 37}, 21--25.}

\bitem { Voshchinnikov N.V.,  Karjukin  V.V. (1994)
%}{ Multiple scattering of polarized radiation in circumstellar dust shells. }{
  \AAp {\bf 288}, 883--896.}

\bitem { Voshchinnikov N.V., Il'in A.E., Il'in V.B. (1986a)
%}{ Light extinction and polarization by dust grains in the interstellar medium:
%  the interstellar extinction curves. }{
 \AF {\bf 24}, 307--320.}
%% (English translation in \Ap).

\bitem { Voshchinnikov N.V., Il'in A.E., Il'in V.B. (1986b)
%}{  Light extinction and polarization by dust grains in the interstellar medium:
% the interstellar linear polarization. }{
 \AF {\bf 24}, 523--534.}
%% (English translation in \Ap).

\bitem { Voshchinnikov N.V., Il'in  V.B., Kholtygin A.F. (1994a)
%}{ Dust and gas in the shells around Herbig Ae/Be stars. }{
 In: Balona L.A. et al.~(eds.)
 Pulsation, Rotation and Mass Loss in Early-Type Stars.
 IAU Symp. N 162, Kluwer, pp.392--393.}

\bitem { Voshchinnikov N.V., Il'in  V.B., Stognienko R. (1994b)
%}{ Comparative analysis of different solutions of
% light scattering problem for non-spherical particles. }{
 In: Passive Infrared Remote Sensing of Clouds and
 the Atmosphere II. Proc.~SPIE, {\bf 2309}, 89--93.}

\bitem { Voshchinnikov N.V., Grinin V.P., Karjukin  V.V. (1995)
%}{ Monte Carlo simulation of light scattering in the envelopes of young stars. }{
 \AAp {\bf 294}, 547--554.}

\bitem { Voshchinnikov N.V., Molster F.J, Th\'{e} P.S. (1996)
%}{ Circumstellar extinction in the shells of pre-main-sequence stars. }{
 \AAp {\bf 312}, 243--255.}

\label{Ref_end}

\end{document}
