Physisorption of an electron in deep surface potentials off a dielectric surface

[摘要] We study phonon-mediated adsorption and desorption of an electron at dielectric surfaces with deep polarization-induced surface potentials where multiphonon transitions are responsible for electron energy relaxation. Focusing on multiphonon processes due to the nonlinearity of the coupling between the external electron and the acoustic bulk phonon triggering the transitions between surface states, we calculate electron desorption times for graphite, MgO, CaO, Al2O3, and SiO2 and electron sticking coefficients for Al2O3, CaO, and SiO2. To reveal the kinetic stages of electron physisorption, we moreover study the time evolution of the image-state occupancy and the energy-resolved desorption flux. Depending on the potential depth and the surface temperature, we identify two generic scenarios: (i) adsorption via trapping in shallow image states followed by relaxation to the lowest image state and desorption from that state via a cascade through the second strongly bound image state in not too deep potentials, and (ii) adsorption via trapping in shallow image states but followed by a relaxation bottleneck retarding the transition to the lowest image state and desorption from that state via a one-step process to the continuum in deep potentials.

[关键词] INELASTIC-SCATTERING;METAL-SURFACES;STATES;DESORPTION;RECOMBINATION;SPECTROSCOPY;PHOTOEMISSION;INSULATORS;PARTICLES;CATALYSTS