The observation of the D2Σ+ state of scandium monoxide molecule: Deperturbation analysis of the interacting C2Πi, v = 4 and D2Σ+, v = 0 states

Abstract

The laser-induced fluorescence spectra of the jet-cooled ScO molecules have been investigated in the 27,400−28,000 cm−1 region at 0.04 cm−1 resolution. The D2Σ+state of ScO, predicted by the earlier ab initio studies, was observed in v = 0 vibration from the ground X2Σ+ state. The C2Πi state, earlier reported by us in vibrations v = 0 − 3, was also observed in v = 4 along with the A2Πr state in v = 14 vibration. The energetically overlapping v = 0 of the D2Σ+and v = 4 of the C2Πi states are perturbed by homogeneous spin-orbit, spin-electronic and J-dependent l-uncouple interactions. The rotational transition wavenumbers of the D2Σ+−X2Σ+(0,0) and C2Πi − X2Σ+(4,0) bands were fitted together using single Hamiltonian matrix that included 2Π and 2Σ+ matrix elements and their off-diagonal elements. The deperturbed D2Σ+, v = 0 state was found to be only 11.5 cm−1 below that of the C2Π3/2, v = 4 sub-state and f- and e-levels respectively cross after J = 12.5 and 28.5. The dispersed fluorescence and wavelength separated excitation spectra were crucial in understanding the spectra and the deperturbation analysis of these interacting vibronic states. The D2Σ+, v = 0 state showed J- and parity-dependent mixing up to ~45% by the C2Πi, v = 4 state and is reflected in the disperse fluorescence spectra. The radiative lifetimes of the A2Πr, C2Πi and D2Σ+ states respectively in 14, 4 and 0 vibrations also indicate that the C − D as well as A − C states interact. The observed sign and relative magnitude of the spin-rotation constant γ of the ground X2Σ+, and excited D2Σ+states are elucidated qualitatively in light of second-order contribution to γ from the A2Πr and C2Πi states.