Analysis of the Infrared Fourier Transform Spectrum of the Spectra of Silane in the Range 2930-3300 cm(-1)

Comprehensive high resolution study of the MSiH4(M=28,29,30) tetradecad stretching bands: Appearance and applications of the isotopic substitution effect in molecules of spherical symmetry

A set of new relations between different spectroscopic parameters of the high symmetry XY4 spherical top molecules is derived on the basis of the general isotopic substitution theory, and a comprehensive high accurate analysis of the five stretching bands (the bands ν1+ν3(F2), 2ν3(F2), 2ν3(E), 2ν3(A1), and 2ν1(A1); the three latter ones are forbidden in absorption) of the tetradecad of the SiH4 molecule is made. The high resolution spectra of MSiH4(M=28,29,30) in their natural abundance were recorded with a Bruker IFS125 HR Fourier transform infrared spectrometer at the Technische Universität Braunschweig, Germany with an optical resolution of 0.003 cm-1 and theoretically analyzed (in this case, for the first time both for all five bands of the 29SiH4 and 30SiH4 species, and for 2ν3(E), 2ν1(A1) bands of the 28SiH4 one). The number of 2713 transitions of the 28SiH4 species (which is more than fourteen times higher compared to analogous studies carried out earlier) belonging to all five ro-vibrational bands of the tetradecad (which are 272, 1897, 15, 369, and 160 transitions of the ν1+ν3(F2), 2ν1(A1), 2ν3(A1), 2ν3(F2), and 2ν3(E) bands) were assigned with the values of quantum number Jmin/Jmax = 5/22, 1/24, 14/20, 4/24, and 6/23, respectively. The analysis of the obtained experimental data was made on the basis of the Hamiltonian model which takes into account all effects and resonance interactions which are possible in such molecular system. The weighted fit of the 2713 transitions led to a set of 40 rotational, centrifugal distortion, tetrahedral splitting, and resonance interaction parameters which reproduce the initial experimental data with an accuracy of drms=4.11×10-4 cm-1. An analogous analysis was made for the two other isotopologues, 29SiH4 and 30SiH4, of silane. In this case, the initial values of the most important spectroscopic parameters of both species were theoretically estimated on the basis of results of the isotopic substitution theory. As the result of the analysis, two sets of the 12 spectroscopic parameters were obtained from the weighted fits for the 29SiH4 and 30SiH4 molecules which reproduce the 461 and 375 initial ro-vibrational transitions with the drms of 3.91×10-4 and 4.9710-4 cm-1.

High resolution FTIR spectroscopy of germane: First study of 76GeH4 in the region of Tetrad of the strongly interacting ν1+ν2,ν1+ν4,ν2+ν3 and ν3+ν4 ro-vibrational bands

The infrared spectra of germane, purified and enriched up to 88.1% of ⁷⁶GeH₄, was measured at the temperature of (22.6±0.1) °C and different pressures with a Bruker Fourier transform infrared spectrometer IFS125HR and analyzed for the first time in the region of 2700-3200 cm^-1 where the stretching-bending Tetrad (ν₁+ν₂,ν₁+ν₄, ν₂+ν₃ and ν₃+ν₄ bands) of the ro-vibrational Octad of germane is located. The 3595 transitions belonging to the eight sub-bands of the Tetrad were assigned and theoretically analysed in the frame of the effective Hamiltonian model. The obtained set of 106 fitted parameters reproduces the initial 3595 experimental line positions with the d_rms=6.81×10^-4 cm^-1. The presence of numerous resonance interactions in the Tetrad is discussed.