Photoelectron counting in the extreme ultraviolet.

The experimental procedures required to operate windowless photomultiplier detectors as photon counters in the extreme uv (xuv) below wavelengths of about 1300 A are reviewed. The requirements for obtaining a well-defined counting plateau for the counting system under conditions of operation frequently met in laboratory vacuum systems are emphasized. The determination of both the absolute quantum efficiency of the detector and the dynamic range over which the response of the detector varies linearly with the rate of photons is described. The experimental methods used to determine the photometric efficiency of a monochromator and its detection system are also discussed.