Experimental verification of the EinsteinA-coefficient used for evaluation of O₂(^1Delta_g) concentration in the chemical oxygen-iodine laser

Abstract

This paper is a contribution to the current discussion on the Einstein coefficient for spontaneous emission (A-coefficient) of singlet delta oxygen, O2(g), that is often used for an evaluation of O2(g) concentration in a chemical oxygen-iodine laser (COIL). The published values of the A-coefficient vary in a wide range, corresponding to a radiative lifetime of O2(g), , from ~53 to ~151 min. This could make an evaluation of COIL operation questionable. In this paper, the Einstein A-coefficient is estimated, based on the comparison of O2(g) concentrations determined by two independent methods: electron paramagnetic resonance and emission spectroscopy. Within the accuracy of the experimental techniques used, the value of the A-coefficient resulting from our investigation is (2.24±0.40) × 10-4 s-1, corresponding to of ~74 min. This result is more consistent with the value of 2.58 × 10-4 s-1 of Badger et al [1] than with the value of 1.47 × 10-4 s-1 reported recently by Mlynczak and Nesbitt [2], who raised doubt about the Badger et al value.

Effect of dynamical‐photochemical coupling on oxygen airglow emission and implications for daytime ozone retrieved from 1.27 μm emission

“…Because the radiative relaxation time of O 2 (a 1 Δ g ) is 1.24 hours and collisional relaxation becomes less important at higher altitudes, the photochemical interaction thus leads to significantly different variations in O 2 ( 1 Δ) and O 3 at a timescale of a few hours. We have adopted a recent value of 2.24 × 10 −4 s −1 for the Einstein coefficient A z 1 [ Lafferty et al , 1998; Spalek et al , 1999] in the model's standard runs. Our model was also tested with a smaller A z 1 of 1.47 × 10 −4 s −1 used by Mlynczak and Nesbitt [1995] in their sensitivity study, and we found that the peak O 2 (a 1 Δ g ) around 95 km would be increased by about 40% when the smaller value of A z 1 is used in the model, leading to a more significant difference between O 2 ( 1 Δ) and O 3 variations.…”

“…The photochemical timescales of various species are determined by collisional quenching and radiative relaxation. The relaxation time of the spontaneous emission of O 2 ( 1 Δ) at 1.27 μ m is 1.24 hours [ Lafferty et al , 1998; Spalek et al , 1999]. Therefore, at high altitude where the collisional quenching becomes less important, the photochemical timescale of O 2 ( 1 Δ) could be comparable or longer than the basic timescale and the transport timescale.…”

Near‐IR oxygen nightglow observed by VIRTIS in the Venus upper atmosphere

“…The vertical profile of the a‐X nightglow is determined by the balance between production of O 2 (a) via reaction and its loss due to radiative decay of the O 2 (a) state and collisional quenching. There has been controversy over the lifetime of O 2 (a) against radiative decay, but recent laboratory measurements [ Cheah et al , 2000; Lafferty et al , 1998; Miller et al , 2001; Newman et al , 1999; Spalek et al , 1999] appear to have converged to a consistent value. The mean lifetime we have computed from these studies, 74 ± 3 min is consistent with recent assessments [ Gamache and Goldman , 2001; Slanger and Copeland , 2003].…”

O2(a1Δg, υ = 0) chemical loss coefficients determined from SABER sunset measurements

“…The measurement by Badger et al [1965] of 2.58 × 10 −4 s −1 has been the most widely used value of the Einstein A ‐Coefficient at 1.27 μ m. More recent measurements from laboratory and atmospheric emission studies have ranged from 1.47 × 10 −4 s −1 [ Mlynczak and Nesbitt , 1995] to 2.24 × 10 −4 s −1 [ Lafferty et al , 1998; Špalek et al , 1999]. Pendleton et al [1996] analyzed ground based FTIR measurements of the evening twilight decay of O 2 ( 1 Δ g ) and found a radiative lifetime of about one hour (∼2.8 × 10 −4 s −1 ).…”