An analysis of vibrations and rotations in the first hydrogen sulfide hexade: the 4$\nu_{2}$H$_2^{32}$S band

The infrared spectrum of the H$_2$S molecule is recorded using a Bruker IFS 125HR Fourier transform spectrometer and studied in the range of 4500–5000 cm$^{-1}$, in which the first hexad of bands of interacting states of the hydrogen sulfide molecule is located (in this particular case, weak band 4$\nu_{2}$ is studied). Four hundred transitions with maximum quantum numbers of $J^{\operatorname{max}}$ = 17 and $K_{a}^{\operatorname{max}}$ = 8 are assigned in the experimental spectrum. These transitions correspond to one hundred thirty two upper vibration–rotation energy levels. The obtained data are analyzed using Watson's model of the effective Hamiltonian. By solving the inverse spectroscopic problem, a set of twenty eight spectroscopic parameters was obtained, which reproduces the initial experimental data with a standard deviation of $d_{\operatorname{rms}}$ = 3.5 $\times$ 10$^{-4}$ cm$^{-1}$.