Rotational and deperturbation analysis of the interacting A2Π1/2, v = 11 ∼ B2Σ+, v = 6 states of yttrium monoxide (YO) molecule

Abstract

The YO molecules in gas-phase were formed by the reaction of the laser produced yttrium plasma with molecular oxygen and subsequently cooled by free-jet expansion. The YO molecules were studied by laser-induced excitation and dispersed fluorescence (DF) spectroscopy at 0.1 cm-1 spectral resolution. The B2Σ+ state was observed in vibrations v=5 and 6 from the X2Σ+ ground state. The anomalously low spin-rotation constant of the B2Σ+, v=6 level compared to the v=0-5 vibrational levels of the B state indicated perturbation. Investigation of the wavelength filtered excitation spectra led to the observation of the A2Π1/2, v=11 spin-orbit component lying 28.5 cm-1 below the B2Σ+, v=6 state. The deperturbation analysis of the interacting pair of B2Σ+, v=6 ∼ A2Π1/2,v=11 states was carried out by incorporating the spin-orbit, spin-electronic and L-uncouple interaction parameters as off-diagonal matrix elements in the 2Σ+-2Π Hamiltonian. The molecular constants of v=11 of the A and v=6 of the B states followed the vibrational trend after deperturbation. The e-parity level of the B2Σ+, v=6 and A2Π1/2, v=11 crossed after J=25.5 and deperturbation analysis estimated J-dependent configuration mixing up to ∼50% for the e-parity and 16% for the f-parity levels. The value of the configuration mixing coefficient of the interacting A and the B states, obtained from the intensity analysis of the observed vibronic bands in the DF spectra, is in agreement with the depertubation analysis. In addition, the Ω=½ spin-orbit components of the A2Π state was observed in v=12 and 13 vibrations and were found to be unperturbed.