Schumann-Runge bands of O2 in Ar, Kr and Xe matrices revisited: potential curves of the B 3Σu− state

Abstract

Absorption/excitation spectra of 16 O 2 isolated in Ar and Kr matrices and 18 O 2 isolated in Ar matrices at 15 K for the B 3 Σ u − ( ν ′)←X 3 Σ g − ( ν ″=0) transitions (Schumann-Runge bands) of O 2 are presented. The spectra in rare-gas matrices differ considerably from the gas-phase spectrum. The cage effect caused by the host lattice has been analyzed using van der Waals interactions between the oxygen atom and rare-gas atoms. Potential curves of the B 3 Σ u − state have been derived for D 3d and D 4h orientations of O 2 in a substitutional site in rare-gas lattices. It has been found that when O 2 occupies D 4h orientation, these potential curves compare closest with the potential curves obtained independently by using the experimental vibronic energies and the method of Oldenberg [O. Oldenberg, Z. Physik 56 (1929) 563]. An analysis of the potential curves indicates that at larger OO separation (> 3.2 Å) in the B 3 Σ u − state, the rare-gas atoms start interacting electronically with the O 2 molecule.