Microwave spectrum and dipole moment of thionyl tetrafluoride

Abstract

Electron diffraction and microwave studies of hionyl tetrafluoride (SOF₄) have been conducted in order to determine its molecular structure. The results from these investigations were however found to be inconsistent.

In view of these controversial findings, a microwave investigation was undertaken to accurately assign the rotational transitions, compare the determined moments with those from prior studies and examine the Stark effect in SOF₄ in order to determine its dipole moment.

Calculations using an Asymmetric Rotor program were made to determine the Stark coefficients for transitions having J = 1-40 and frequencies between 12-27 MHz. Absorption peaks were identified as had been predicted by theoretical calculations. The spectrum was very rich and exhibited many strong Q-branch transitions (ΔJ=0). Most were high J transitions whose Stark components could not be resolved. The R-branch transitions (ΔJ=1), were observable for only low J transitions and at very low Stark voltages.

Stark peaks were not well resolved for the low J transitions; most of them had been masked by the strong Q-branch transitions. Data from the 1(0,1) ----> 2(1,1) transition at 14049 MHz gave a dipole moment of 0.97 Debye.

A least squares fit of the observed frequencies correlated well with those from the structure D4, proposed by Hedberg and Hedberg. The rotational constants and moments of inertia were calculated to obtain the values: A = 4181.0 ± 0.04 MHz B = 3289.8 ± 0.04 MHz C = 3206.3 ± 0.04 MHz I_a= 120.9 ± 0.02 amu Ų I_b= 153.6 ± 0.02 amu Ų I_c= 157.6 ± 0.02 amu Ų