LaseRitz: Far-Infrared Laser Line Assignment and Prediction by the Ritz Combination Principle, with Application to Methanol and Hydrazine.

A "LaseRitz" program is described for the systematic assignment and prediction of far-infrared laser (FIRL) transitions for a given molecule, such as methanol or hydrazine, which can be generated by optical pumping with known laser lines. The input data set for the program consists of identified molecular energy levels in ground and excited vibrational states, as compiled by our Ritz assignment program from the analysis of infrared (IR) bands and the FIR ground state spectrum. The program scans the data set for appropriate IR matches with an input list of laser pump lines for CO(2), N(2)O, etc., and generates an output table of all possible FIRL lines consistent with the molecular selection rules and lying within a prescribed wavenumber range. Initial tests on CH(3)OH have led to three likely new FIRL assignments; for N(2)H(4), assignments have been found for 14 new FIRL transition systems and verified for five others. Lists have been produced (deposited as supplementary data with the JMS archive reached at www.idealibrary.com or available on request from the authors) of CH(3)OH and N(2)H(4) FIRL lines potentially accessible by optical pumping with regular, sequence-band, hot-band, and isotopic CO(2) lines, plus N(2)O lines for N(2)H(4). The systematic approach with the LaseRitz program is more global and rigorous than earlier line-by-line studies, permitting calculation of all FIRL wavenumbers to spectroscopic accuracy. Copyright 2000 Academic Press.