DOUBLE-PHOTON PHOTOELECTRIC EMISSION FROM ALKALI ANTIMONIDES

Nonlinear response in photoelectron emission from alkali antimonides, such as Cs3Sb and K3Sb, under intense laser irradiation was observed directly. The photocurrent was proportional to the incident laser power at lower intensity, but it showed quadratic response at higher intensity. Energy distribution of the emitted electrons in the quadratic region coincided for the most part with that excited by the natural light with a wavelength half that of the laser. These results seem to present experimental evidence for a double-photon absorption process in the nonlinear photoemission caused by intense irradiation. © 1968 The American Physical Society.