A quantum model for photoemission from metal surfaces and its comparison with the three-step model and Fowler–DuBridge model

Abstract

This paper studies a quantum mechanical model for photoemission from a metal surface due to the excitation of laser electric fields, which was developed by solving the time-dependent Schrödinger equation exactly. The quantum model includes the effects of laser fields (wavelength and intensity), properties of metals (Fermi energy and work function including Schottky effect), and the applied dc field on the cathode surface. Shorter wavelength lasers can induce more photoemission from electron initial energy levels further below the Fermi level and, therefore, yield larger quantum efficiency (QE). The dc field increases QE, but it is found to have a greater impact on lasers with wavelengths close to the threshold (i.e., the corresponding photon energy is the same as the cathode work function) than on shorter wavelength lasers. The quantum model is compared with existing classical models, i.e., the three-step model, the Fowler–DuBridge model, and the Monte Carlo simulation based on the three-step model. Even though with very different settings and assumptions, it is found that the scaling of QE of the quantum model agrees well with other models for low intensity laser fields. When the laser field increases, QE increases with the laser field strength in the longer laser wavelength range due to the increased contributions from multiphoton absorption processes.