Vibration-rotation molecular constants for the ground and ( ν3 = 1) states of 32SF 6 from saturated absorption spectroscopy

Abstract

An analysis has been made of the vibration-rotation structure of the ν 3 band of 32SF 6 from measurements, by saturated absorption spectroscopy, of the frequencies for 136 transitions in close coincidence with CO 2 and N 2O laser lines in the 28-THz region. After deconvolution of the fine structure lines from their hyperfine structures, the centers of vibration-rotation transitions are given with a 5-kHz uncertainty. They are analyzed using the tensor Hamiltonian of Moret-Bailly, developed to the fifth order of approximation. An iterative procedure, using full diagonalization of the Hamiltonian matrices, leads to a very accurate determination of 18 effective molecular constants of the ( v 3 = 1) excited state, together with 6 constants of the ground state (both for scalar and tensor terms). For instance, the inertial constant of the ground state is β 0 = B 0 = 0.0910842001(10) cm −1, the vibrational energy is α = ν 3 = 948.10252337(40) cm −1, and the Coriolis coupling coefficient is ζ 3 = 0.69344341(20). The recorded transitions, ranging from P(84) to R(94), are reproduced with a standard deviation σ d = 28 kHz ⋍ 0.93 × 10 −6 cm −1 . A few transitions remain out of the fit, and the possibility of resonances with close vibrational levels is briefly discussed. We also give the predicted positions for SF 6 transitions in close coincidence with laser lines of various isotopic species of CO 2.