Lifetime of the2p33sS5Metastable State of Oxygen

Abstract

The lifetime of the $2p^{3}3s{}_{}{}^5{}_{}{}^{}S$ metastable state of oxygen has been measured using the time-of-flight technique. The velocity distribution of metastable atoms resulting from the dissociation of excited oxygen molecules is sampled and detected at two positions, 1.8 and 6.6 m from the pulsed electron gun used to bombard the ground-state molecules effusing from a source slit. A comparison of the number of metastables within specific velocity intervals at the two detectors determines the number which decay in flight and yields an experimental plot of the number which decay vs time of flight. The lifetime $\tau$ is then obtained from the slope ($=-\frac{1}{\tau }$) of a straight line least-squares fitted to the decay plot. The result is $\tau =185\mathrm{}\pm 10$ μsec.