High resolution study of MSiH4 (M=28, 29, 30) in the Dyad Region: Analysis of line positions, intensities and half-widths

Abstract

The infrared spectra of SiH4 in natural abundance (92.23% of 28SiH4, 4.68% of 29SiH4, and 3.09% of 30SiH4) were measured in the region of 600–1200cm−1 with a Bruker IFS 120HR Fourier transform spectrometer, analyzed and compared with the results available in the literature. More than 3500 transitions with Jmax.=27 were assigned to the dyad bands ν4 and ν2 of 28SiH4 (the band ν2 is allowed in Raman, but forbidden in absorption spectra for symmetry reasons, and its transitions appear in absorption spectra only because of strong Coriolis interaction with the ν4 band). Rotational, centrifugal distortion, tetrahedral splitting, and interaction parameters for the ground, (0100) and (0001) vibrational states were determined from the fit of experimental line positions. The obtained set of parameters reproduces the initial experimental data with accuracy close to experimental uncertainties. The results of the analogous analyses of the 29SiH4 and 30SiH4 isotopologues are also presented (the numbers of the assigned transitions are here more than 1360 and 1120). An further analysis of about 790 experimental ro-vibrational lines in the dyad region of 28SiH4 was performed using the Voigt profile to simulate the measured line shape and to determine experimental line intensities. A set of 4 effective dipole moment parameters for the dyad of 28SiH4 was obtained on that basis from the weighted fit, which reproduce the initial experimental intensities of about 790 lines with the drms=5.6%. Analogous analyses were made for the two other isotopic species, 29SiH4, and 30SiH4. A detailed line list of transitions in the region of 750–1150cm−1 is generated. The half-widths of 40 ro-vibrational lines (Jup.max.=16) are studied from the multi-spectrum analysis, and self-pressure broadening coefficients are determined.