A study of the fine rotational structure of the silane molecule absorption spectrum was carried out for the first time. The high-resolution spectrum of 28SiD4 was recorded in the 1260-1480 cm-1 spectral range the vibrational ν2+ν4 (F1,F2) and 2ν4 (F2) bands were theoretically analyzed. Rotational, centrifugal distortion, tetrahedral splitting and resonance interaction parameters of the upper vibrational states were obtained from the weighted least square fit method. The set parameters obtained reproduces the initial vibrational-rotational structure of the ν2 + ν4 (F1, F2) and 2ν4 (F2) bands with an accuracy of drms = 3.9 · 10-4 cm-1.

The high-resolution spectrum of the 72GeH4 molecule was recorded on a Bruker IFS 125HR Fourier spectrometer with an optical resolution of 0.003 cm-1. The line positions were analyzed for ten interacting vibrational-rotational bands 3ν4 (1F2, F1, 2F2), v2+ 2ν4 (1E, F1, F2, 2E) and 2ν2+v4 (1F2, F1, 2F2) in the range 2350-2750 cm-1. As a result of the analysis, 1726 experimental lines were identified with the maximum value of the quantum number Jmax = 17; then used in the fitting procedure with parameters of the effective Hamiltonian. The resulting set of 35 spectroscopic parameters describes the vibrational-rotational structure of the spectrum with drms = 7.5 · 10-4 cm-1.