The 10 μm Infrared Band of Silicate Dust: A Laboratory Study Comparing the Aerosol and KBr Pellet Techniques

Abstract

The profile of the silicate 10 $\mu$m IR band contains important information about the evolutional stage of dust in circumstellar environments and the possible ongoing process of planetesimal formation. In order to extract this information, the observed band profiles are compared with calculated or laboratory-measured absorption cross sections of amorphous and crystalline grains with different sizes and compositions. We present in this study the first laboratory measurements of the 10 $\mu$m band profiles of nonembedded, i.e. free-flying, particles of amorphous and crystalline Mg$_2$SiO$_4$ (with two different particle shapes), amorphous and crystalline MgSiO$_3$, and crystalline olivine. We compare the spectra with those measured on embedded grains and discuss the potential of the new experimental method for comparison with observed spectra, as well as for future studies of agglomeration and surface manipulation of the grains.