First comprehensive high resolution study of the 28SiH4 octad bending bands

The infrared spectrum of mono-silane was measured at varied experimental conditions with a Bruker Fourier transform infrared spectrometer IFS125HR and analyzed for the first time in the 2600–2950 cm⁻¹ region of the octad where 16 strongly interacting triply excited bending bands are located. The 3505 transitions belonging to fourteen sub-bands of the octad (with the exception of unappeared $3{\nu }_4\left(A_1\right)$ and $3{\nu }_2\left(A_2\right)$) were assigned ($J^{\text{max}}=20$) and theoretically analyzed in the frame of the effective Hamiltonian model. The obtained set of 139 fitted parameters reproduces the initial 3505 experimental line positions with the $d_{\text{rms}}=7.3\times 10^{-4}$ cm⁻⁴. A list of assigned experimental transitions is presented as the Supplementary data 2 to this paper.