2-PHOTON IONIZATION PROCESS IN OPTICAL BREAKDOWN OF CESIUM VAPOR

Optical breakdown of cesium vapor by Q-switched laser light is studied. The threshold laser power density for the breakdown is observed over fairly wide range of the cesium atoms density. A pair of probes are inserted in the vicinity of the focal point for the purpose of detecting the occurrence of breakdown. The magnitude of the threshold laser power density and its dependence on the atom density measured by us are different from those reported by Rizzo and Klewe. The present result confirms the validity of the two-photon ionization mechanism suggested by Bebb and Hall. © 1969 The American Institute of Physics.