Energetics and dynamics of laser-assisted field evaporation: Time-dependent density functional theory simulations

Abstract

High positive electrostatic (dc) field can break the bonds in molecules and strip away atoms from the solid surfaces. The dynamics of this field evaporation under laser pulse is studied for a ${\mathrm{H}}_{2}$ molecule and a ${\mathrm{Si}}_{4}$ cluster using time-dependent density functional theory combined with molecular dynamics. This allows us to monitor the position and charge state of the evaporated atom in real time. Our simulations demonstrate that the critical dc field for the evaporation is lower if the molecule/cluster is illuminated by a laser pulse. The behavior of the evaporation threshold as a function of laser intensity and dc field is in qualitative agreement with experiments and provides important insights into the mechanisms of laser-assisted field evaporation. Additionally, the laser-assisted field evaporation is found to be sensitive to the laser energy according to the photoabsorption spectra that demonstrate a pronounced redshift in the lower energy region at higher dc field values.