Rotational Structure and Perturbations in the B4Π- X4Σ − (1, 0) Band of VO

Abstract

The (1, 0) band of the B 4Π- X 4Σ − transition of VO has been analyzed rotationally, from Doppler-limited discharge emission and laser excitation spectra. The B 4Π, v = 1 level is heavily perturbed by a vibrational level of the a 2Σ + state and, with the extra complexity caused by the 51V nuclear hyperfine structure, could be analyzed fully only by extensive wavelength-resolved laser-induced fluorescence experiments. Making use of data from the corresponding perturbations in B 4Π, v = 0 and assuming that the vibrational dependence of the spin-orbit matrix element can be represented by a vibrational overlap integral, it has been possible to deduce the vibrational numbering of the perturbing a 2Σ + state without having to use isotopic data. It is found that the a 2Σ +, v = 0 level lies near 10412 cm −1, and that B 4Π, v = 1 is perturbed by a 2Σ +, v = 3. The a 2Σ + state comes from the same electron configuration, (4 sσ) (3 dδ) 2, as the X 4Σ − ground state. The phases of the spin-orbit matrix elements between 4Π and 2Σ + states must be chosen consistently in order to obtain a correct understanding of the rotational perturbations. A consistent set of phases is obtained with 〈 2Σ +, F 2 | H SO | 4Π 1 2 , f〉 = 〈 2Σ +, F 1 | H SO | 4Π 1 2 , e〉 = [formula] 〈 2Σ +, F 2 | H SO | 4Π − 1 2 , f〉 = −〈 2Σ +, F 1 | H SO | 4Π − 1 2 , e〉 = A/2, where A = 〈 2 Σ + || H spin- orbit || 4 Π〉.