Depth of secondary photoelectron emission from CsI monocrystals and films

The photoelectric yield of CsI in dependence on the depth of production of primary photoelectrons in a crystal was investigated with the aim of finding the depth of the yield of secondary photoelectrons (L). The investigations were carried out for single-crystal CsI samples and films in the photon energy range of 60 eV <= hν <= 160 eV, which corresponds to variation in the absorption coefficient within the range of 0.35-4.4x105 cm-1. The spectra were measured at room temperatures. The films were prepared by evaporation onto nickel-coated glass substrate. The measurements were carried out for films of different thickness from 135 A to 2000 A. The experiment on measuring the photoelectric yield in the ultrasoft X-ray range proved to be a simple and reliable method for determining L. It was found that L for CsI equals approximately 215 A