Abstract

The oxygen molecule is known to absorb and emit photons by single-molecule transitions as well as cooperatively by pair-molecule transitions or transitions involving O₄ complexes^1,2. From the excited singlet states ¹Δ_g(0) and ¹Δ_g (1), near infrared emissions at 1.06 μm and 1.27 μm take place as showin in Fig. 1, although they are generally weak due to the forbidden nature of the transitions. Also it is to be noted that the excited-state oxygen pair molecules Produce fluorescence spectra in the visible region as indicated in Fig. 1. Since the metastable ¹Δ_g (0) state is the first excited one, the fluorescence lines from the ¹Δ_g (0)· ¹Δ_g (0) state at 630 nm and 700 nm exhibit rather stronger intensities than those for other transition lines. However, the transition from the ground ${}^3{\Sigma }_g^{-}\left(0\right)$ state to the excited ¹Δ_g (1) state is almost on resonance with the Nd:YAG laser output at 1.06 μm. Hence strong absorption of this radiation provides large concentrations of singlet oxygen molecules in this state from which various excited states are induced by energy transfer processes².

© 1984 Optical Society of America