The observation of the C2Πi state of ScO: Rotational and deperturbation analysis of the interacting C2Πi and B2Σ+ states

Abstract

The jet-cooled laser-induced fluorescence spectra of ScO molecules have been investigated in the 24,500–27,400 cm−1 region at 0.04 cm−1 resolution. The ab initio predicted C2Π state in group IIIb transition metal oxide molecules, but heretofore undetected, was observed in ScO molecule in vibrations v = 0–3. In addition, the higher vibrational levels of the earlier reported A2Π and B2Σ+ states, respectively in v = 12–13 and v = 5–8 were also observed. The vibrational levels of these states energetically lie in proximity, resulting in perturbations between the B and C states. The deperturbation analysis of these bands are reported. Among the observed bands, the deperturbed band origin (BO) of the C2Π1/2-X2Σ+ (0,0) sub-band was found to be only 6 cm−1 above the BO of B2Σ+-X2Σ+ (6,0) band. The rotational transition wavenumbers involving the v = 0–3 levels of the C2Πi state and the v = 5–8 levels of the B2Σ+state from the ground state were fitted together using single a Hamiltonian matrix that included 2Πi and 2Σ+ matrix elements and their off-diagonal elements coupling vibrational levels of these states. The depurturbed band constants and interaction parameters were determined and were used to generate Dunham coefficients. The Yl0 and Yl1 coefficients were used to generate Rydberg-Klein-Rees (RKR) potential curves. Vibrational radial, and overlap integrals were computed from the RKR potential, and the off-diagonal matrix elements coupling the electronic wavefunctions of the B and C states were determined. The B2Σ+, v = 6 level shows J- and parity-dependent mixing up to ~50% by the C2Π1/2, v = 0 level and this is also reflected in the radiative lifetimes of these states.