Photon interactions in a cesium beam

Photoionization of excited cesium atoms in the 62P3/2 - state has been studied in a triple crossed-beam experiment. A thermal beam of cesium atoms was intersected by one photon beam of wavelength 8521A that served to excite the atoms and another photon beam with wavelengths below 5060A that served to ionize the excited atoms. The resulting ions were detected with a channel electron multiplier. All background effects were discriminated against by chopping the beam of exciting radiation and by analyzing the net count rate with digital synchronous techniques. The relative cross section for photoionization fo Cs(62P3/2) has been measured from threshold (5060A) to 2500A. The results fall off faster than the theoretical calculations of Weisheit and Norcross