High–resolution study of the pentad bending triad region of silane: The 2ν₂,ν₂+ν₄ and 2ν₄ bands of ²⁸SiH₄,²⁹SiH₄ and ³⁰SiH₄

The high resolution infrared spectra of SiH₄were recorded with Bruker IFS120 and IFS125 HR Fourier transform infrared spectrometers at an optical resolution of 0.0021 and 0.0025 cm⁻¹and analyzed in the region of 1600–2100 cm⁻¹where the first bending overtone 2ν₂,2ν₄and combinational ν₂+ν₄bands are located. The number of 640/1114/2667 transitions with J^max= 23 were assigned to the bands 2ν₂(A₁- and E-type sub–bands), 2ν₄(A₁-, E- and F₂-type sub–bands) and ν₂+ν₄(F₁- and F₂-type sub–bands) of the ²⁸SiH₄molecule. The subsequent weighted fit of experimentally assigned transitions was made with the Hamiltonian model which takes the resonance interactions between seven vibrational states ((0200,A₁),(0200,E),(0101,F₁),(0101,F₂),(0002,A₁),(0002,E)and (0002,F₂)) into account. As the result, a set of 73 fitted parameters was obtained which reproduces the initial 4421 experimental transitions with the d_rms=3.31×10⁻⁴ cm⁻¹. On the basis of the obtained results, 4940 hot transitions were assigned in the high resolution spectra of the Dyad region studied before. The corresponding analysis was made for the ²⁹SiH₄and ³⁰SiH₄isotopologues. A line list of 12,698 experimental transitions for both the “cold” and “hot” transitions of all three isotopologues is presented.