Emission and Relaxation of Electronically Excited O₂ Doped in a Low Temperature N₂ Crystal

Abstract

Oxygen molecules doped in a low temperature N₂ crystal were irradiated at 240-260 nm. Two emission band systems were observed, one from the v′ = 0 level of A′ ³Δu state to X³Σg^-. state and the other, from the v′ = 0 level of c¹Σu^-. state to at a¹Δg state, independent on the excitation wave length. The latter emission grew together with the decay of the former emission at around the same rate after the pulsed laser excitation, which implies that the vibrational levels of c state lying below the v′ = 0 level of Ω = 3 of A′ state are populated from the v′ = level of A′ state, though some additional mechanism for populating the c state may exist. The rate was found to become larger with the increase of the crystal temperature. It was also found that the excitation spectrum obtained by monitoring the A′–X emission was the same as that obtained by the c–a emission. The progress of vibrational relaxation, coupling with the intersystem crossing between the Herzberg states, will be discussed.