Transition Radiation and Optical Bremsstrahlung from Electron-Bombarded Thin Gold Foils

Abstract

Unbacked gold foils 340- and 530-Å thick were bombarded by a 1.5-μA electron beam of energy 25 to 100 keV. The light emitted at 30° from the foil normal on the beam exit side was analyzed between 2500 and 5500 Å with a vacuum ultraviolet spectrometer and a glan prism polarizer. The spectral distribution and absolute photon yield in the plane containing the electron beam and photon direction agree well with the transition radiation theory if the bremsstrahlung contribution is assumed to be unpolarized. The photon intensity perpendicular to the plane (of incidence) has the dependence on primary energy indicated by the bremsstrahlung theory of Gluckstern, Hull, and Breit, but only 40% of the expected absolute value. The discrepancy is thought to be due to neglect of optical absorption and refraction in the calculation.