Microwave spectrum of sulfur difluoride in the first excited vibrational states vibrational potential function and equilibrium structure

Abstract

Microwave spectra of SF 2 in the first excited states of the three normal modes were observed and analyzed. A comparison of the observed inertia defects in the ν 1 and ν 3 states with those calculated by omitting the contributions of the Coriolis interaction between the two modes led to a ν ̃ 1 - ν ̃ 3 vibrational frequency differences of 25.72 ± 0.33 cm −1, with ν 1 being definitely higher. The inertia defect in the ground state and our measured values for the inertia defect in the ν 2 state and for the ν ̃ 1 - ν ̃ 3 difference were combined with the centrifugal distortion constants of Kirchhoff et al. [J. Mol. Spectrosc. 48, 157–164 (1973)] to improve the harmonic force field. The interaction constant between the two SF stretching coordinates was determined precisely. The third-order and the cubic anharmonic potential constants were calculated from the observed vibration-rotation constants. The equilibrium structure was determined to be r e( SF) = 1.58745 ± 0.00012 A ̊ and θ e (FSF) = 98.048 ± 0.013°.