Photodetachment ofO3−in a Drift Tube

The drift-tube photodetachment technique was used to measure the absolute photodetachment cross section, and the solar photodetachment rate of ${\mathrm{O}}_3^{-}$. The energy dependence of the cross section $\sigma$ was measured with the use of 18 color filters. By fitting the data with a least-squares program, we found that $\sigma =\left[\alpha \mathrm{}\right(E-3.0\mathrm{})+\beta ]H(E-E_0)$, where $\alpha =(5.6\mathrm{}\pm 1.7)\times {10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$/eV, $\beta =(8.7\mathrm{}\pm 1.6)\times {10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$, $E_0=1.99\mathrm{}\pm 0.10$ eV. $E_0$ is the threshold energy and $H$ is the Heaviside step function. The solar photodetachment rate was 0.082±0.015 ${\sec }^{-1\mathrm{}}$. The ${\mathrm{O}}_3^{-}$ ions were identified by mobility.