High-resolution infrared spectra and simultaneous rovibrational analysis of the nu(2), nu(3), nu(5), and nu(6) bands of H3SiF

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 fundamen tal bands nu(2) (A(1)), 990.851 cm(-1); nu(3) (A(1)), 875.011 cm(-1); nu(5) (E), 962.213 cm(-1) and nu(6) (E), 729.528 cm(-1) A total number of 7241 t ransition wavenumbers (including 53 perturbation-allowed transitions) with J' less than or equal to 49 have been fitted by taking into account various Coriolis interactions, alpha-resonance terms, and e-type interactions betw een and within the vibrational levels nu(2) = 1, nu(3) = 1, nu(5) = 1, and nu(6) = 1. The strongest interaction in this system of levels is the x-y Co riolis coupling between the nu(2) = 1 and nu(5) = 1 vibrational states. How ever, it turns out that the x-y and z-type Coriolis interactions also have to be introduced explicitly between the nu(5) = 1 and nu(6) = 1 states as w ell as the x-y Coriolis interactions between nu(3) = 1 and nu(5) = 1, and n u(3) = 1 and nu(6) = 1 states, in order to fit the data quantitatively. The standard deviation of the fit was sigma = 8.6 x 10(-5) cm(-1) for 7241 tra nsition wavenumbers and 68 fitted parameters. The sign relations between th e fitted parameters and the possibility of fitting the parameters in differ ent schemes are discussed. The results have been used to find close coincid ences between the frequencies of the CO2 laser lines and the transition wav enumbers of the nu(2) and nu(5) bands of H3SiF for the main natural isotopo mer. We report integrated absorption band strengths which are important for infrared laser chemistry. (C) 1999 academic Press.