Perturbations of the A′1Π and C1Σ+ states of CaO

Abstract

Laser induced fluorescence spectra for jet-cooled CaO have been used to examine the higher vibrational levels of the A′1Π(Xσπ−1) state (v = 10–17) and the v = 6–8 vibrational levels of the C1Σ+(Bσσ−1) state. A perturbation of v = 17 of the A′ state was evident, caused by a spin-orbit mediated interaction with the b3Σ+(Ω = 1)(Xσσ−1) v = 14 level. Ro-vibrational constants for the A′ state were obtained by fitting to the data for nominally unperturbed levels. The average radiative lifetime for the A′1Π(Xσπ−1) state v = 10–17 levels was 2.6 μs, with no measurable dependence on v. This was consistent with the theoretical prediction of a relatively small transition dipole moment for the A′1Π–X1Σ+ band system.A homogeneous perturbation of the C1Σ+(Bσσ−1) v = 7 level was examined by means of dispersed laser induced fluorescence (DLIF) and radiative lifetime measurements. The DLIF spectra clearly demonstrate that the perturbing Ω = 0+ state is a component of a triplet state. Intense transitions from this state to the a3Π(0+)(Xσπ−1) state were observed. Configurational arguments are presented that support assignment of the perturbing state as the v = 12 vibrational level of the previously unobserved g3Π(0+)(Bσπ−1) state.