Above-threshold ionisation without space charge

Abstract

The multiphoton ionisation of xenon has been studied using a picosecond Nd:YAG laser and a time-of-flight electron spectrometer with a collection angle of 2 pi sr. In the absence of space charge effects, suppression of the first electron peak is observed at an intensity of 5*1012 W cm-2 in linear polarisation, while saturation occurs at 1.3*1013 W cm-2. In circular polarisation, the same effect is observed at a slightly lower intensity. The intensity dependences of the first three peaks have been measured.