Commission 14: Realistic Numerical Synthesis of Molecular Spectra

Abstract

Spectrocopy is the classical diagnostic tool of astrophysics. Intensities and line shapes of well identified emission and/or absorption atomic and molecular features are used to provide information on species concentrations, and degree of excitation, from which gas kinetic, rotational, vibrational, electronic and excitation “temperatures” can be inferred when LTE conditions exist. Departures from LTE can also be determined spectroscopically. Diagnostic interpretation of spectra in optically thin circumstances is fairly straightforward. However, in optically thick conditions when the photon mean free path is very much less than the geometrical path, the emission spectrum is controlled by the absorption coefficient (Armstrong and Nicholls, 1972), (see equation 4a).