High-resolution Fourier transform spectra and rotational analysis of monoisotopic H374Ge35Cl and H374Ge37Cl in the ν2/ν5/2ν3 region near 850 cm−1

Abstract The gas phase infrared spectra of the monoisotopic germyl chloride species H 3 74 Ge 35 Cl (7435) and H 3 74 Ge 37 Cl (7437) in the ν 2 / ν 5 /2 ν 3 region near 850 cm −1 have been studied with a resolution (fwhm) of ca. 0.002 cm −1 employing a Fourier transform spectrometer. A total of 4628 and 3461 transitions of (7435) and (7437), respectively, have been assigned with K max = 15 and J max = 80 for ν 2 ( a 1 ) and ν 5 ( e ). For 2 ν 3 of (7435), K max and J max were 6 and 61, respectively. Precise J -dependent ground state constants up to sextic coefficients have been determined from a fit (σ ⋍ 1.3 × 10 −4 cm −1 ) of 1635 and 751 combination differences for (7435) and (7437), respectively. One pair of excited state levels split by Δ l = ±1, Δ k = ⊣2 interactions has been observed, and A 0 (in connection with D K 0 determined previously) of (7437) has been obtained from the related normal and perturbation-allowed transitions. Strong Coriolis interaction, |ζ 2,5 i | ⋍ 0.65 , i = x , y , with positive intensity perturbation occurs between ν 2 ( a 1 ) and ν 5 ( e ). For (7437), the perturbation by 2 ν 3 ( A 1 ) is local and restricted to the ( kl ) = −8 sublevels of ν 5 . In contrast, ν 2 and 2 ν 3 are sufficiently close in (7435) that extended Fermi interactions, | W 233 F | = 1.27 cm −1 , negative intensity perturbation, become dominant. The observed transitions have been fitted, σ ⋍ 1.3 × 10 −4 cm −1 , to excited state parameters, and a model taking into account Fermi, Δ l = Δ k = ±1, Δ l = Δ k = ±2 and Δ l = ±1, Δ k = ⊣2 interactions has been employed. The following rounded vibrational frequencies ( 7435 7437 ) have been determined: ν 2 0 , 847.650 847.456 , ν 5 0 , 873.844 873.833 , and 2 ν 3 0 , 843.070 827.607 cm −1 .