Deperturbation analysis of the ν3 fundamental and hot bands of gaseous BeH2

Free gaseous BeH2 was first synthesized in 2002 at the University of Waterloo and thehigh resolution infrared emission spectra of BeH2 molecule was recorded at 1500 °C with aFourier transform spectrometer [1]. The antisymmetric stretching fundamental band (ν3), aswell as several hot bands involving ν1 and ν2 was rotationally analyzed, for which the effect ofrotational ℓ-type doubling and ℓ-type resonance were included [1-3]. Small localperturbations were observed in some of the vibration-rotation bands of BeH2. Since both ofthe matrix isolation and high level ab initio calculations on BeH2 showed that ν3 ≈ 3v2, localperturbations in the (v ,v ,v ) 1 2 3 levels due to the third order Coriolis interaction with thenearby (v ,v 3,v 1) 1 2 3   levels, would be desirable. These perturbations were analyzedrecently for the 001 level of BeD2 [4], but no deperturbation analysis was performed for theBeH2 molecule. In this work we report rotational assignment and deperturbation analyses oftwo new hot bands, i.e., 031→030 and 041→040, for the BeH2 molecule, which resulted indetermination an accurate value for the ν2 fundamental frequency of the bending mode.