| Abstract |
Dust grains in stellar environments re-emit star light as infrared (IR) radiation at the frequencies of lattice vibrations of the solid material. Hence the IR emission of various astronomical environments is dominated by characteristic vibrational bands of dust grains which provide information upon their particular chemical compositions, on grain growth and crystallization, and lattice structure. The analysis of IR spectra obtained by observations is quite complex and not straightforward because the physical and chemical properties play a decisive role in the shape and strength of the distinctive spectral features. Although both experimentally measured and simulated spectra are utilized for interpretation of observed spectra, if anything, theoretical models for calculating scattering, absorption, and extinction efficiencies by particles have been applied in general since one can easily change the input parameters as grain size, the grain geometry, and composition of grain. Nevertheless, there are no theoretical approaches available which can deal with the whole particle conditions e.g. irregularity, heterogeneity, size, and agglomeration state for arbitrary particles. On the other hand, the experimental spectroscopic IR absorption/transmission and reflection measurements of dust grains have been performed by means of different techniques, such as pellet, thin section, and adopting aerosol techniques. The IR spectroscopy can be accomplished in different experimental conditions with various purposes. A greatest merit of laboratory work is that it is nowadays possible to perform experiments under realistic conditions with advanced technology. Conversely, a disadvantage is that it is very difficult to determine the physical properties of dust grains during experiments (e.g. morphological aspects). I will introduce what experimental IR spectroscopy can do including information about difference in experimental spectra obtained by another techniques, advantages and disadvantages of each approach, problems, and possibilities in this presentation. |
