VUV Spectrometer-Detector System Calibration Using Synchrotron Radiation

Abstract

A method of absolute calibration of a VUV spectrometerdetector system is presented in which continuum synchrotron radiation is used. Calibration of the optical system is performed for the purpose of absolute measurements of electron impact photoemission cross sections for discrete atomic (molecular) transitions in the VUV wavelength region. A large computer controlled multiadjustable manipulator is used for positioning the spectrometerdetector system with respect to a beam of synchrotron radiation. The manipulator allows rotation with respect to two perpendicular axes, one collinear with the electron beam, and the other collinear with the spectrometer entrance slit. Using these rotations, a beam of synchrotron radiation is scanned across the grating surface resulting in a precise simulation of the source geometry encountered in the electron -atom collision source. In this way the absolute response of the spectrometerdetector system and the geometrical factors encountered in the electron -atom source are determined in an integral fashion allowing absolute photoemission cross sections to be determined with unparalleled precision.