A new method for obtaining the cross section for photoionization of photoexcited cesium is presented. The salient feature of this experiment is to use three crossed beams, i.e., two light beams intersecting a beam of cesium atoms. The cross section is determined by counting the ions produced by the two step process: Cs (6S) + h[upsilon]₁ --\u3e Cs (6P) ; Cs (6P) + [upsilon]₂ --\u3e Cs⁺ + e⁻ The relative cross section for the second step has been obtained from threshold (5060 Å) to 2500 Å. The excitation light source used in obtaining this cross section was a rf resonance lamp, but the possibility of using a GaAs laser as this light source was also investigated. A GaAs laser was thermally tuned to the 6S - 6P transition wavelength in cesium, 8521 Å, and it was found that in this way the hyperfine levels of the ground state of cesium could be selectively depopulated. Although excellent results were obtained in this portion of the study, the low duty cycle of the lasers that we had available made them unsuitable for the photoionization experiment --Abstract, page i
