ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
A detailed re-investigation of the (0,0) and 211 bands of the A˜ 2Πu–X˜ 2Πg transition of 11BO2, near 545 nm, has been carried out from spectra taken at sub-Doppler resolution. Avoided crossings are found to occur between the 2Σ and 2Δ vibronic components of the v2=1 level of the A˜ 2Πu state. These perturbations are the first known examples of K-resonance crossings, which result from an interplay of the electronic Λ-type doubling and the vibrational l-type doubling in a state where the electrostatic parameter ε is small. It turns out that perturbations of this type must always occur in a 2Π electronic state if the ratio A/εω2 is large enough, but have not been seen until now for lack of suitable data. Their existence allows an unusually complete description of the orbital angular momentum effects in both the A˜ 2Πu and X˜ 2Πg states. It has been necessary to fit the avoided crossings by a full matrix treatment of the K resonance. In addition the A˜ 2Πu state, although it appears to be unperturbed at lower resolution, shows an astonishing number of very small random rotational perturbations. These arise from vibronic coupling between the A˜ 2Πu and X˜ 2Πg states of BO2 through the ν3 vibration, which has species σ+u; their presence is consistent with the explanation given by Kawaguchi et al. [Mol. Phys. 44, 509 (1981)] for the sizable negative anharmonicity of the ground state ν3 vibration. About 20% of the available ground state energy levels at 18 300 cm−1 appear to be active in causing level shifts and splittings in the A˜ 2Πu state. The matrix elements are quite small, ranging up to about 600 MHz, but the great number of perturbations indicates the onset of chaotic behavior.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.457931
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