Abstract

In a vacuum chamber pumped down to 1 × 10⁻⁸ Torr, Xe gas was leaked at a rate so that the Xe pressure inside the vacuum chamber was 1 × 10⁻⁶ Torr. An intense 1-ns CO₂ laser was used to ionize the gas. The ejected electrons were detected with a retarding potential energy spectrometer. On the energy spectrum there are two peaks. One starts at a few electron volts and centers around 50 eV. The other starts at 230 and centers around 350 eV. Referring to the saturation intensity measured by Yergeau et al.¹ the peak at 350 eV can be explained with the acceleration of electrons created in the ionization of Xe by the ponderomotive force. The low-energy peak at 50 eV was attributed to a similar acceleration process of electrons created in the ionization of some impurities. This speculation was confirmed by repeating the same experiment with Xe of higher purity.

© 1987 Optical Society of America