title: High-Resolution Infrared Spectra and Simultaneous Rovibrational Analysis of the nu2, nu3, nu5, and nu6 Bands of H3SiF.
abstract: A high-resolution FT infrared spectrum of H3SiF (resolution 0.0024 cm-1) in the region 620-1130 cm-1 was measured and used to analyze the fundamental bands nu2 (A1), 990.851 cm-1; nu3 (A1), 875.011 cm-1; nu5 (E), 962.213 cm-1; and nu6 (E), 729.528 cm-1. A total number of 7241 transition wavenumbers (including 53 perturbation-allowed transitions) with J' </= 49 have been fitted by taking into account various Coriolis interactions, alpha-resonance terms, and l-type interactions between and within the vibrational levels v2 = 1, v3 = 1, v5 = 1, and v6 = 1. The strongest interaction in this system of levels is the x-y Coriolis coupling between the v2 = 1 and v5 = 1 vibrational states. However, it turns out that the x-y and z-type Coriolis interactions also have to be introduced explicitly between the v5 = 1 and v6 = 1 states as well as the x-y Coriolis interactions between v3 = 1 and v5 = 1, and v3 = 1 and v6 = 1 states, in order to fit the data quantitatively. The standard deviation of the fit was varsigma = 8.6 x 10(-5) cm-1 for 7241 transition wavenumbers and 68 fitted parameters. The sign relations between the fitted parameters and the possibility of fitting the parameters in different schemes are discussed. The results have been used to find close coincidences between the frequencies of the CO2 laser lines and the transition wavenumbers of the nu2 and nu5 bands of H3SiF for the main natural isotopomer. We report integrated absorption band strengths which are important for infrared laser chemistry. Copyright 1999 Academic Press.