Collisional quenching of O ₂ ( ¹ Δ _g )

The paper reports determinations of rate constants for the physical deactivation of O$_2$($^1\Delta_g$) by gases present in the atmosphere. A modified discharge-flow technique was employed, and relative concentrations of O$_2$($^1\Delta_g$) were measured by a photoionization method. The rate constants for the process \begin{equation*}\tag{1}O_2(^1\Delta_g) + M \rightarrow O_2 + M\end{equation*} were $\leqslant$ 1.1 x 10$^{-19}, \leqslant$ 2.1 x 10$^{-19}$, $\sim$ 2.4 x 10$^{-18}$, $\sim$ 3.9 x 10$^{-18}$, $\sim$ 1.5 x 10$^{-17}$ (cm$^3$ molecule$^{-1}$s$^{-1}$) for M = N$_2$, Ar, O$_2$, CO$_2$, H$_2$O respectively. The rate constant for quenching by dry air was measured directly to be 4.3 $\pm$ 0.7 x 10$^{-19}$ cm$^3$ molecule$^{-1}$s$^{-1}$; this value is consistent with the most recent estimate based on [O$_2$($^1\Delta_g$)] in the upper atmosphere (3.5 $\pm$ 1.0 x 10$^{-19}$ cm$^3$ molecule$^{-1}$s$^{-1}$; W. F. J. Evans, private communication). Wall deactivation efficiencies varied from 1.2 x 10$^{-5}$ to 2.3 x 10$^{-5}$.