The spectroscopic analysis of the v2 = 1, v5 = 1, and v3 = v6 = 1 infrared vibration system of H3SiI

Abstract The ν 2 (A 1 )/ν 5 (E)/ν 3  + ν 6 (E) band system of H 3 28 SiI was investigated using Fourier transform infrared spectra recorded from 820 to 1100 cm − 1 at a resolution of 2.0 × 10 − 3  cm − 1 . In total, 11,903 transitions were assigned. Additional 1466 transitions reaching the v 3  =  v 6  = 1 state were obtained from the ν 3  + ν 6  − ν 6 and ν 3  + ν 6  − ν 3 hot bands near 360 and 590 cm − 1 , respectively. Moreover, 30 highly accurate CO 2 laser sideband transitions of the r Q 0 branch of ν 5 ( J.M. Frye , W. Schupita , and G. Magerl , J. Mol. Spectrosc. 128 , 427 ( 1988 )) were implemented in the data set with J max ″  = 140 and  K max ″  = 21. To adequately reproduce the complex pattern of interacting levels the Hamiltonian employed included 14 off-diagonal terms. These comprise x , y Coriolis ro-vibration resonances, between ν 2 /ν 5 , ν 2 /ν 3  + ν 6 and ν 5 /ν 3  + ν 6 , and the anharmonic Fermi resonance between ν 5 /ν 3  + ν 6 . All these resonances strongly perturb the v 2  = 1, v 5  = 1, and v 3  =  v 6  = 1 excited states whose rounded deperturbed vibrational term values are 904.5, 941.1, and 953.7 cm − 1 , respectively. In addition, the Δ l  = Δ k  = ± 2 l -resonance was found to be active within the v 3  =  v 6  = 1 state and between v 5  = 1 and v 3  =  v 6  = 1; the Δ l  = ± 2 , Δ k  = ∓ 1 l -resonance within the v 5  = 1 state and between v 5  = 1 and v 3  =  v 6  = 1 was established, as well as the Δ l  = ± 1 , Δ k  = ∓ 2 α resonance between v 2  = 1 and v 5  = 1. A standard deviation of the fit, 0.48 × 10 − 3  cm − 1 , resulted which is ca. three times the estimated precision of experimental wavenumbers. Improved J -dependent ground state parameters of H 3 SiI were obtained by fitting 5420 combination differences, σ(fit) = 0.22 × 10 − 3  cm − 1 .