Determination of transient negative ion lifetimes using Rydberg atoms

[摘要] Potassium Rydberg atoms are used to investigate the lifetimes, on a picosecond timescale, of transient negative ions formed during dissociative electron attachment to CCl$sb4$ and CF$sb3$I. The transient negative ions are formed during Rydberg electron transfer reactions of the type$${m K}(n{m p})+ABo{m K}sp{+}+ABsp{-*}o{m K}sp{+}+Asp{-}+B$$For low values of principal quantum number $n (n sbsp{sim}{<} 20)$ the electrostatic interaction between the ${m K}sp{+}-ABsp{-*}$ and ${m K}sp{+}+Asp{-}$ ion pairs perturbs the ion trajectories. As a consequence, the final angular and velocity distributions of the ${m K}sp{+}+Asp{-}$ ions are dependent on the lifetime of the $ABsp{-*}$ intermediate ion. The $ABsp{-*}$ lifetime is determined by comparing product ion distributions, determined using position sensitive detection techniques, with the results of a Monte Carlo simulation that models the kinematics of the reaction. The data show that the lifetime of the excited $m CFsb3Gammasp{*}$ intermediate formed by Rydberg electron capture is short, $sbsp{sim}{<}2$ ps, and that the lifetime of the CCl$sbsp{4}{-*}$ intermediate is $7.5pm2.5$ ps.

[发布机构] Rice University

[效力级别] physics