The First Si–H Stretching Overtone of H3SiD: Emergence of Local Mode Effects

Abstract

The FTIR spectrum of H3SiD in the 4100–4500-cm−1region was recorded at Doppler-limited resolution, and four bands were studied. At lower wavenumbers, two strong bands, which in the local mode picture can be assigned to (200,E) (ν0= 4308.5667 cm−1) and (200,A1) (ν0= 4307.8441 cm−1), were analyzed, and at higher wavenumbers, two weaker bands, namely (110,E) at 4378.1950 cm−1and (110,A1) at 4375.9763 cm−1, were analyzed. A total number of ∼1900 lines in the strong dyad and 1000 lines in the weak one were assigned and fitted with standard deviations of the residuals ≈0.0008 cm−1. The strong system (200) is close to local mode behavior, with nox,yCoriolis term needed and only a smallzCoriolis term, and simple arithmetic relations between vibration–rotation parameters are fulfilled as expected. The local mode behavior of the weak system (110) is less pronounced, butzandx,yCoriolis effects are smaller than in the Si–H stretching fundamentals. Comparison of computed and observed spectra provided a good estimate for the ratios of transition moments of the different bands: they are, in absolute value, proportional to 3.5:1.75:1:1 for (200,E), (200,A1), (110,E), and (110,A1), respectively.