High-resolution fourier transform spectra and rotational analysis of monoisotopic H 3Si 79Br in the ν2, ν5 region near 900 cm −1

Abstract

The infrared spectrum of H 3Si 79Br in the region 850–1050 cm −1 has been recorded with a resolution of 0.005 cm −1. The vibrational fundamentals ν 2 ( a 1) and ν 5 ( e) associated with the symmetric and degenerate SiH 3 bending mode have been rotationally analyzed, and a total of 3888 transition frequencies have been fitted, with σ = 5.9 × 10 −4 cm −1. ν 2, 929.752 17(6) cm −1, and ν 5, 946.425 69(4) cm −1, strongly interact by Coriolis x, y resonance, ζ 2,5 y ∼ 0.637. Except for three weak and mostly local resonances, the data were fitted by a conventional model involving diagonalization of 3 × 3 matrices accounting for l(±2, ±2) and Coriolis x, y resonance simultaneously. An accidental rotational resonance of ν 5 with 2 ν 3, mainly affecting the kl = −13 level with level crossing between J′ = 16 and 17, has been evaluated. The analysis of the l(±2, ⊣1) resonance near to the crossing between J′ = 57 and 58 of the kl = +2 and −3 levels, as well as the accidental l(∓1, ±2) resonance between kl = 1 and K = 3 of ν 5 and ν 2, respectively, permit the determination of A 0, 2.842(5) cm −1. Improved ground state parameters D J 0 and D JK 0 have been obtained from ground state combination differences.