Electric Field Effects in the Radiative Decay of Photoexcited Autoionizing States in Helium

V. L. Jacobs, Jeffrey A. Davis

Yurij V. Zhmenyak, Vasyl S. Vukstich, I.P. Zapesochnyi

G.G. Bogachev

A. Mihelič, M. Žitnik

Photon yields resulting from radiative cascades of photoexcited helium singly and doubly excited states in a dc electric field are presented. The combined effect of the spin-orbit and the field-induced mixing on the yields are examined.

M. Žitnik, Francis Jean Penent, P. Lablanquie +5 more

We have measured the lifetimes of $^{1}P^{e}$ $(n=9--12)$ doubly excited states in static electric fields $(1--6\phantom{\rule{0.3em}{0ex}}\mathrm{kV}∕\mathrm{cm})$ by observing the decay of the fluorescence signal as a function of time. The effects of the field on these helium states below the second ionization threshold are twofold: their excitation becomes possible due to the Stark mixing with the optically allowed $^{1}P^{o}$ series, and their lifetime is strongly modified by the opening of the autoionization channel, not accessible in zero field. Although the electric field represents only a tiny perturbation of the atomic potential, a substantial shortening of the lifetimes below $100\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$ is observed. This is the simplest quantum system where the ratio of autoionization to fluorescence decay probability can be effectively controlled by an electric field of moderate strength.

S. Danzan, B. Zhadamba, Ts. Sukhbaatar +2 more