Microwave spectrum, structure, quadrupole coupling constants, and dipole moment of bromotrifluorosilane

Abstract

The microwave spectra of four isotopic species of bromotrifluorosilane, 28SiF 3 79Br, 28SiF 3 81Br, 30SiF 3 79Br, and 30SiF 3 81Br, have been measured. Analysis of the two main species has led to considerable refinement of earlier published constants. Rotational constants for 28SiF 3 79Br are B 0 0 = 1550.060(1) MHz, D J = 0.166(4) kHz, and D JK = 1.245(9) kHz. The nuclear quadrupole coupling constants arising from 79Br and 81Br were revised to 344.0(1) and 287.4(1) MHz, respectively. The average zero-point structure has been determined as SiB = 2.1559 ±0.0037 A ̊ , , SiF= 1.5591±0.0052 A ̊ FSiBr = 110.38±0.19 °, , FSiF= 108.55±0.19 °. The dipole moment was determined, taking full account of Stark-quadrupole interaction, to be μ = 0.835(7) D. Two vibrational satellite series have also been analyzed. The most prominent series arises from a degenerate vibration at about 230 cm −1 with q 6 = 1.17 and α 6 = 1.19 MHz. The second series is derived from the degenerate asymmetric deformation of the SiF 3 top at about 380 cm −1 with q 5 = 0.31 and α 5 = −1.31 MHz.