“Anomalous” Photoelectric Effect in the Ultrafast Electron Diffraction Method

Electron-pulse probing of fast laser-induced processes has allowed the direct observation of the structural dynamics in matter with a high spatiotemporal resolution. A thin gold film has appeared to be a convenient photocathode, and photoelectron emission has been induced by femtosecond ultraviolet radiation with a photon energy of about 4.65–4.75 eV (in particular, \(\hbar \)ω \( \cong \) 4.65 eV for the third harmonic of the Ti:sapphire laser). For the linear photoelectric effect, this energy contradicts the reference work function W_Au \( \cong \) 5.1–5.3 eV of pure metal. Reasons for such contradiction have been analyzed and good agreement with experimental data has been reached with a model proposed for the generation of photoelectron pulses.