Extended FTIR high resolution analysis of hydrogen sulfide in the region of the second hexad: Line positions and ro–vibrational energies of H₂ ^MS (M=32,33,34)

The high resolution infrared spectra of hydrogen sulfide H₂ ³²S were recorded with a Bruker IFS 125HR Fourier transform infrared spectrometer (Zürich prototype ZP2001) and analyzed in the region of 5650–6660 cm⁻¹ where six interacting bands (2ν₁+ν₂, ν₁+ν₂+ν₃, ν₁+3ν₂, 3ν₂+ν₃, 5ν₂ and ν₂+2ν₃) of the second hexade are located. 2452 transitions with maximum values of the quantum numbers J^max = 18/19/13/14/14/11 and K_a ^max = 10/11/8/11/7/5 were assigned in the experimental spectra to the 2ν₁+ν₂, ν₁+ν₂+ν₃, ν₁+3ν₂, 3ν₂+ν₃, 5ν₂ and ν₂+2ν₃ bands. On this basis, 194/216/108/104/90/9 upper ro–vibrational energies (more than 1.4 times higher number of both transitions and upper energy values compared to the preceding studies) were obtained for the upper vibrational states (210), (111), (130), (031), (050) and (012). These data were used in the weighted fit of the Watson Hamiltonian parameters. The 172 parameters obtained from the fit reproduce the 721 initial energy values of six vibrational states (2452 transitions) with the root mean square deviation d_rms=7.1×10⁻⁴ cm⁻¹. The 534 transitions belonging to the 2ν₁+ν₂ and ν₁+ν₂+ν₃ bands of H₂ ³⁴S (197 upper energy values; about 1.5 times higher number for the ν₁+ν₂+ν₃ band and more than two times higher number for the 2ν₁+ν₂ band) were recorded and analysed. For the first time, 177 transitions (70 upper energy values) were assigned to the ν₁+ν₂+ν₃ band of H₂ ³³S.