High-resolution infrared spectroscopy of molecular ions

Abstract

Experimental techniques of high-resolution infrared absorption spectroscopy are described with an emphasis on the modulated hollow-cathode discharge techniques. Among the recent results, the rq fundamental band of HOCS+ |iq — 3435.16 cm-1) and the X2IT and a4E” system of NH+ (t0 = 2903.17 cm-1 in X2II state, = 2544.30 cm-1 in a4E~ state, and A£(a4E_ —X2n) — 323.90 cm-1) are presented to illustrate the quality and type of information that the high-resolution ion spectroscopy can provide. Another topic discussed is the abundance ratio [HCO+]/[H O C +] as measured in the laboratory and its astrophysics implications. The measurement has been made possible by our recent detection of the rq fundamental band of HOC+ (iq, — 3268.03 cm""1). A rate-equation analysis was performed by assuming a reaction scheme to derive the rate constants of several key reactions.