Dispersed laser fluorescence spectroscopy of the perturbation facilitated B1Π-b3Σ+(1, 1) band of CaO

Abstract The observation and analysis of the B 1 Π- b 3 Σ + (1, 1) band by dispersed laser-excited fluorescence spectroscopy are presented. A perturbation mechanism is suggested which explains the observation of singlet-triplet fluorescence, the observation of only one spin component of the b 3 Σ + state, and detection of the f -symmetry levels of the a 3 Π 0 ( v =3) state. A spin-orbit matrix element between a 3 Π 0 ( v =3) and b 3 Σ + ( v =1) is derived here, based on the atomic-ion-in-molecule ligand field model for the electronic structure of CaO. This is the first reported direct experimental observation of the lowest 3 Σ + state of CaO. The molecular constants obtained from a least-squares fit of the term energies of the b 3 Σ 0 + ( v =1) state are (in cm −1 ): T 1 =10073.3(10)( relative to X 1 Σ + v=0, J=0) B1=0.4040(23) with 1 σ uncertainties in parentheses.