Low-temperature spectroscopic measurements of the ‘dimol’ transitions of singlet molecular oxygen [O2(a1Δg)]

Abstract

By observing the emissions at 634 and 703 nm from a discharged flow in oxygen, the spectra and emissivity of the cooperative, ‘dimol’, transitions of O₂(a¹Δ_g) have been studied between 100 and 323 K. The broad spectral maximum, characteristic of these transitions, narrows as the temperature is lowered. The emissivity remains constant, disagreeing with previous absorption measurements where it was found that the absorptivity increased at lower temperatures. The results are discussed in terms of a theory which treats the emission as arising from the collisional interaction of the two excited molecules; the theory fits both the present results and previous high-temperature measurements.