Spectral and temporal characteristics of photostimulated exoemission from coldworked metals

In an attempt to elucidate the plausible mechanism(s) of the photostimulated exoemission of metals, the spectral distributions of photoemission and time evolution of photocurrents from coldworked (milled, abraded, deformed) or chemically cleaned samples of Al, Cu, Fe and Cu:Be have been investigated. The experiments have been made in gas environment with a flow counter as well as with an electron multiplier in a vacuum of 5×10−10 mbar. All tested samples exhibit after the above treatments photostimulated exoemission (PSEE) – a considerable increase of the photoelectric yield in the visible and near-ultraviolet region. After treatment PSEE relaxes to lower intensities (decays) in the gas environment, but arises further if stored in vacuum after in situ abrasion of the surfaces. Obtained results support the concept of mechano-induced PSEE from metals, which considers the uprise of PSEE as a result of the mechanical removal of the native oxide film from the surface and attributes its decay to the recovery of the oxide, which attenuates the photoelectron flux from the metal substrate. PSEE can be applied to monitor the oxidation of the coldworked details.