A new effect in multiphoton photoeffect of a gold surface induced by picosecond laser pulses

Abstract
A bandwidth‐limited 15‐psec laser pulse is used to induce multiphoton photoelectric emission from a gold metal cathode. The wavelength is tuned between 10 580 and 10 620 Å to investigate the transition from a four‐photon to a five‐photon photocurrent j from a gold surface. This transition gives rise to a new effect marked by a dramatic change of the slope n=∂ logj/∂ logI, where I is the laser intensity.