Study of Electrons Produced in Laser Induced Multi - Ionization of Gas Atoms.

The process of multi-photon ionization of a low pressure gas by a ruby laser light pulse was studied. In particular, the number of electrons and the total energy gained by the electrons from the ionization process itself, and from their subsequent acceleration by the intense ruby laser light, were measured. The number of electrons released was found to have a sixth-order power dependence on the light intensity. A mechanism for the ionization process via a resonant intermediate level is suggested. Two independent techniques were used to measure the energy spectra of the ionization electrons. The first method was based on the time of flight from the interaction region to the detector. In the second method a retarding potential was applied just before the detector. The peak values of the two spectra showed good agreement.