On the perturbations in the (000-000) band of the BaOH [formula omitted] transition

Abstract

A laser-spectroscopic investigation of the (000-000) band of the B ̃ 2 Σ +- X ̃ 2 Σ + transition of the BaOH molecule has been performed. The analysis shows that the upper level is badly perturbed, presumably by a Σ vibronic level of the A ̃ 2 Π 3 2 state. A deperturbation calculation is presented, giving molecular constants for both the interacting levels. However, due to the probable existence of additional perturbations, as yet unobserved, it is found that different sets of rotational constants are needed for the e and f levels of the B ̃ 2 Σ + (000) state. Furthermore, studies of A ̃ 2 Π- X ̃ 2 Σ + emission, following B ̃ state excitation, reveal that the dominating B ̃ - A ̃ relaxation mechanism is perturbative and collisional rather than radiative, as had been proposed earlier.