FTIR Study of the ν1/ν4 Bands of D3Si35Cl near 1600 cm−1

Abstract

The ν1 (A1, 1583.22 cm−1) and ν4 (E, 1615.33 cm−1) Si–D stretching bands of monoisotopic D3Si35Cl have been studied by FTIR spectroscopy with a resolution of 3.3×10−3 cm−1. We have assigned 2341 rovibrational lines for ν1 (Jmax=70, Kmax=19) and 6207 for ν4 (Jmax=75, Kmax=27). Both (ΔK=±1, Δℓ=±1) and (ΔK=±2, Δℓ=∓1) interactions connect the v1=1 and v4=1 levels, the latter exerting moreover a weak ℓ(2, 2) interaction. These interactions were taken into account in a nonlinear least-squares fit, refining 29 free parameters with a standard deviation of 0.257×10−3 cm−1 over 6722 nonzero-weighted data. Blended lines and about 250 of the 330 lines belonging to the K=11 subband of ν1 and the KΔK=−6 subband of ν4 were zero-weighted because they are locally perturbed respectively by the neighboring upper states of the 2ν3+ν6 (E, 1561.95 cm−1) and 3ν3 (A1, 1604.81 cm−1) bands. Equivalent fits were obtained for altogether three different models obeying constraints according to the theory of unitary equivalent reductions of the rovibrational Hamiltonian. By means of a band contour simulation both the transition moment ratio |M1:M4|=0.67 and a positive sign of the Coriolis intensity perturbation were determined.