High resolution study of MGeH4 (M=76, 74) in the dyad region

•High resolution analysis of the dyad of 74GeH4 and 76GeH4.•Resonance interactions in spherical top molecules.•Determination of spectroscopic parameters.

The infrared spectrum of GeH4 (88.1% of 76GeH4, 11.5% of 74GeH4, and minor amounts of three other stable isotopic species in the sample) was measured in the 700-1080 cm−1 region with a Bruker IFS 125HR Fourier transform interferometer (Nizhny Novgorod, Russia) and analyzed. 1922 transitions with Jmax.=26 were assigned to the ν4 and ν2 bands of 76GeH4 (ν2 is a symmetry forbidden absorption band, and its transitions appear in the spectrum 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 an accuracy close to experimental uncertainties. The result of analogous analysis of the 74GeH4 isotopologue (the number of assigned transitions is 788) is also presented.