1 research outputs found
Infrared Studies of the Symmetry Changes of the <sup>28</sup>SiH<sub>4</sub> Molecule in Low-Temperature Matrixes. Fundamental, Combination, and Overtone Transitions
Infrared
spectra of <sup>28</sup>SiH<sub>4</sub> in argon and nitrogen matrixes
at low temperature 6.5β20 K in the region of overtone and combination
transitions were recorded for the first time. Additionally, the high-resolution
spectra were obtained in the fundamental region. The frequencies and
the relative intensities of all bands were determined. The set of
experimental data suggests that the symmetry of molecules studied
in the matrixes is different from the symmetry of the free molecules
because of an interaction with the environment. The symmetry of <sup>28</sup>SiH<sub>4</sub> changes from <i>T</i><sub><i>d</i></sub> to <i>C</i><sub>3<i>v</i></sub> on transition from the gas phase to a nitrogen matrix and to <i>D</i><sub>2<i>d</i></sub> on transition to an argon
matrix. A modeling of SiH<sub>4</sub> molecule force fields explains
the experimental data as a change of a force constant of the selected
SiH bond in the case of SiH<sub>4</sub> in the nitrogen matrix or
force constants of two opposite angles in the case of SiH<sub>4</sub> in the argon matrix. In spite of small values of these changes,
they result in noticeable spectroscopic effects: the band splitting
and appearance of new bands in matrix spectra compared with spectra
of free SiH<sub>4</sub>. The interpretation of transitions in the
fundamental and combination regions was performed