Excitation, inversion, and relaxation mechanisms of the HCN FIR discharge laser

Abstract

Millimeter/submillimeter rotational absorption spectroscopy has been used as a diagnostic probe of a cw HCN discharge laser. This sensitive technique allowed in situ absolute population measurements of a number of vibrational states of HCN (including the upper lasing state) and other pertinent molecules. This unique set of data, which was obtained under a variety of discharge and laser conditions, is directly related to excitation, inversion, and relaxation processes. Along with elucidating several fundamental aspects of inversion and relaxation these results also strongly indicate that the primary laser excitation mechanism is near-resonant energy transfer from vibrationally excited nitrogen, N2 (v=1), to the fundamental symmetric stretching mode of hydrogen cyanide, HCN(100), and subsequent thermal population exchange between HCN (100) and the upper laser state, HCN (110).