Translational energy distribution in hot electron mediated photodesorption: a one-dimensional quantum mechanical calculation of NO/Pt(111) and SO2/Ag(111)

An one-dimensional (along the adsorbate–surface coordinate) quantum mechanical calculation within the framework of the Antoniewicz model has been performed for understanding the translational energy distribution in desorption of chemisorbed systems such as NO/Pt(111) and SO2/Ag(111). The potential energy curve of the ground state is constructed from known adsorption properties and that of the excited state is constructed by adding a Coulombic term for the image charge stabilization. For these model potentials, the one-dimensional Schrödinger equation is solved exactly using the Cooley–Numerov integrator. This enables one to follow the time evolution of the wavepacket while the excited state is allowed to decay exponentially with a mean lifetime. The translational energy distributions of the desorbed molecules are obtained by mapping out the Franck–Condon overlap of the final state wavefunction with the continuum states of the ground PES. The effects of the shape of the potential energy curves and the residence lifetime in the excited state are examined. It is found that the calculated average translational energies compare with those experimentally measured for both systems. It also appears that the translational temperature is hotter for adsorbates that are more strongly bonded to the substrates.