Recent Advances in Calculating Molecular Collision Rates

Interstellar clouds are mainly composed of hydrogen molecules whose molecular spectra are difficult to record. Major other components are polar molecules, whose rotational and ro-vibrational spectra are readily observed. Inelastic collisions of molecules with H2 and electrons are important processes to understand the formation and intensities of molecular spectral lines. We have calculated the interaction energy and various inelastic cross-sections and rates, for two important constituents of the interstellar media, H2O and HC3N.