Secondary electron energy distributions for gold as excited by C Kα (277 eV) and Al Kα (1487 eV) x rays

The secondary electron energy distributions for a gold photocathode as excited by C Kα (277 eV) and Al Kα (1487 eV) x rays have been measured. The shapes of the energy distributions are essentially the same for these two x-ray photon excitation energies. For thick evaporated gold samples on glass substrates (at 150 °C and 3×10−8 Torr), the secondary electron energy distributions peak at about 1 eV and have a FWHM of about 4 eV. As measured immediately after ion cleaning, the distributions peak at about 2 eV and have a FWHM of about 6.6 eV. Approximately 5 h after ion cleaning, the measured distributions appear as those obtained before ion cleaning. The work function of the evaporated gold photocathode temporarily increases by 1 eV upon ion cleaning.