Photoelectric Yields in the Vacuum Ultraviolet

Abstract

Absolute photoelectric yields of Ni, Cu, Pt, Au, W, Mo, Ag, and Pd are presented for the spectral region from 1400 to 473 A. Measurements were obtained for commercially pure polycrystalline surfaces which were treated in various ways including heat treatment in vacuo and in various gas atmospheres at reduced pressures. Surfaces, heat treated in vacuo, gave reproducible yields ranging from 10−3 electrons per photon at 1400 A to 10−1 electrons per photon at 500 A. Although untreated samples exhibited a maximum in the region studied, this maximum disappeared after heat treatment resulting in most cases in a broad plateau extending from 1000 A to 500 A. At wavelengths longer than 1000 A a decrease in yield was observed. Representative experiments with a Ni cathode, heat treated in vacuo then exposed to O2 at reduced pressures, indicated that the maxima for untreated surfaces were caused by adsorbed gases and metallic oxide formation. The absolute error in the values of the photoyields was estimated to be within ±15%.

Intrinsic Photoemission of Alkali Halides

“…The yield found for platinum is in reasonable agreement with the thermocouple measurements of Watanabe and Matsunaga 20 and the measurements of Walker, Wainfan, and Weissler. 8 The platinum calibration curve is plotted in Fig. 2.…”

“…In semiconductors and insulators the electrons undergo nearly elastic scattering from phonons and impurities and inelastic scattering due to the ionization of impurities and the excitation of valence electrons to conduction levels. 7 The magnitude of the volume photoelectric yield of metals is relatively low (about 0.1 electron/photon), 8,9 whereas the yield of a pure insulator with a small electron affinity is somewhat greater (about 0.3 electron/photon). 10,11 The alkali halides are insulators with large forbidden gaps of about 8 eV and electron affinities of the order of 1 eV.…”

Charge distribution about an ionizing electron track in liquid helium

“…When an excited helium atom or excimer, He * 2 [23], radiatively decays to the ground state, it does so with the emission of a photon with a energy between 13 and 20 eV. Upon hitting a metal surface in vacuum such a photon has a probability in the range of 5 to 15% [24,25] of ejecting an electron, depending on the material and surface conditions. In liquid helium the situation is much different.…”

Experimental tests for the acceleration of trapped particles

“…The proton spectrum from several Mev to 1, 000 Mev should be analyzed along with Yriagnetic-field measurements to determine if betatron or Fermi acceleration appreciably alters the energy of these protons. The photoelectric yield is on the order of 10 percent above 12 ev for most metals and drops to 1 percent at 10 ev, at least for th-metals (with relatively large work functions) which were studied by Walker, Wainfan, and Weissler (1955). The photoelectric yield could remain above 1 percent at photon energies as low as 6 to 8 ev for some metals with small work functions.…”