Millimeter-wave spectra and revised spectroscopic parameters of methylsilane

Abstract

Rotational spectra of methylsilane in the ground and several torsionally excited states were measured in the region from 87 to 350 GHz with Doppler-limited resolution. For some of the transitions in the ground vibrational state, the internal rotation splitting has been recorded with sub-Doppler resolution via the saturation technique. Transitions in the torsional states with v t ≤ 2 have been assigned and analyzed with a least-squares procedure, employing a direct diagonalization method for calculating the torsion-rotation energy levels. A phenomenological Hamiltonian has been developed to describe on the free-internal rotor basis the internal and overall rotation of symmetric-top molecules. The potential barrier of methylsilane to internal rotation was determined to be V 3 ≈ 590.5 cm −1.