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

Abstract

Oxygen molecules doped in a low temperature N crystal were irradiated at 240-260 nm. Two emission band systems were observed, one from the v' 0 level of A' 3A state to X3E. state and the other, from the v' 0 level of cE. state to atAg state, independent on the excitation wavelength. 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 3 of A' state are populated from the v' 0 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.

Photodynamics in oxygen doped solid deuterium

“…The measured fluorescence lifetimes at 4 K are 5.4Ϯ0.3 s and 216Ϯ15 s in D 2 and N 2 , respectively. The latter value is in agreement with the earlier measurement of Goodman et al 6͑a͒ who reported a lifetime of 234Ϯ10 s in N 2 , at 4.2 K, and is consistent with the more recent measurements by Kajihara et al 10 Since we do not observe any c→a emission under these conditions, and since the only known nonradiative relaxation channel of AЈ(vϭ0) is via energy transfer to c, we assume that these lifetimes are determined primarily by radiative relaxation. As already documented in rare gas matrices, these orbitally forbidden transitions are dramatically enhanced.…”

“…The electronic spectroscopy of oxygen isolated in rare gas solids, and in solid nitrogen is well established. [7][8][9][10] It exhibits interesting, isotopically dependent relaxation dynamics. Resonant or dissociative excitation of the O 2 in the UV, above 5 eV, produces vibrationally relaxed emission over the AЈ ( 3…”

“…11 The AЈ state is nested amid the A( 3 ⌺ u ϩ ) and the c( 1 ⌺ u Ϫ ) potentials. When the temperature of the matrix is raised, in Ar, in N 2 , 6,10 and in Kr, 17 the AЈ state of O 2 transfers its population to the c state: the AЈ→X emission subsides, and is replaced by the c( 1 ⌺ u Ϫ )→a( 1 ⌬ g ) emission. The vibrational resonance required in this process is isotopically sensitive, such that in 16 -18 O 2 the c→a emission dominates even at low temperature.…”