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

Absorption/excitation spectra of 16O2 isolated in Ar and Kr matrices and 18O2 isolated in Ar matrices at 15 K for the B3Σu−(ν′)←X3Σg−(ν″=0) transitions (Schumann-Runge bands) of O2 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 3Σu− state have been derived for D3d and D4h orientations of O2 in a substitutional site in rare-gas lattices. It has been found that when O2 occupies D4h 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 3Σu− state, the rare-gas atoms start interacting electronically with the O2 molecule.