Theoretical investigation of the influence of isotope mass on chemicurrents during adsorption of H on K(110)

Using our recently developed method for calculation of electron–hole (e–h) spectra in adsorption on metal surfaces Phys. Rev. B 19:165407, 2009], we investigate the system H/K(110). Comparing to our previous results for H/Al(111), we show that the narrower conduction band of K in contrast to Al leads to notable differences in the excitation spectra of electrons and holes. We also find that our results do not obey the scaling of the number of excited charge carriers above a certain energy barrier with the particle's velocity, which is in our case mainly depending on the isotope mass. Instead, we find a different (approximately m^1/6 rather than m^1/2) scaling. Extrapolating our results to adsorbates with large masses, we expect larger electronic excitations than from the “forced oscillator” approach. This makes the electronic dissipation channel for energy more important even for heavy adsorbates. Our results are in qualitative agreement with other theoretical and experimental results.