Infrared Spectroscopy of Ions of Astrophysical Interest

Abstract

Molecular ions are key species in the chemistry of the interstellar medium (ISM). Given the low temperatures and number densities typically occurring in the ISM, one of the few available mechanisms to form more complex molecules is through barrierless exothermic reactions, as it is the case for many ion-molecule reactions. Ions are highly reactive species but they can be formed efficiently in the ISM by cosmic-ray or ultraviolet ionization and can survive for relatively long times due to the few collisions they suffer. On earth, molecular ions are "exotic" species much more difficult to produce in appreciable quantities. Electrical discharges in low pressure gases form cold plasmas which can be used to produce molecular ions in abundances high enough to enable their spectroscopic study.