Photodesorption and work function study of long-living excited electronic states on metal surfaces

Photodesorption of Na atoms from rough Na surfaces

“…This finding agrees with other indirect experimental evidence from work function measurements that desorption in the case of a rough sodium film occurs from long-lived ͑30 fs͒ excited electronic states, which are established at surface structural defects and include localization of conduction electrons. 10 However, this lifetime of the electronically excited state is still short compared to the time scale of the nuclear motion, which is given by the vibrational frequency of the atoms in the clusters and is thus of the order of a picosecond. Consequently, by applying the ''conventional'' DIET ͑desorption induced by electronic transitions͒ picture 86 one would expect to observe a MB velocity distribution with a ''temperature'' Tϭu/k 87 with u the slope of the excited state curve at the critical point ͑actually u ϭs 2 t c /m with s the slope͒ and the electronic relaxation time at the critical distance.…”

“…The probability for electron ͑and ion͒ emission should be proportional to exp(ϪW/k B T electron ), where the work function of Na is Wϭ2.31 eV. 10 Hence for values of T electron Ϸ10 4 K an appreciable amount of electrons is expected. An accurate determination of the electron-phonon coupling constant, which is presently underway, should allow us in the near future to provide realistic values of the nonequilibrium temperatures of the hot electron gas.…”

Observation of strong optical absorption at the surface of small particles

“…The separation of the total absorption into additive volume and surface terms assumes that absorption due to surface roughness comes into play in addition to plasmon-polariton excitation of the nonlocalized conduction electrons. This is justified here, since surface roughness makes possible additional excitation of special localized electronic states, which, as mentioned above, have already been found to play an essential role in the nonthermal desorption of atoms and dimers [5][6][7][8].…”

“…Recent experimental (see, e.g., Refs. [5][6][7]) and theoretical work [8] has indeed shown that the electronic properties of the surface can be critical. Their special role manifests itself, for example, in thermal and non-thermal desorption of atoms and dimers [9][10][11] or in optical second-harmonic generation [ 12].…”

Non-thermal laser-induced desorption of metal atoms with bimodal kinetic energy distribution

“…An essential process among the variety of lasersurface interactions is non-thermal desorption of atoms, ions and molecules (see e.g. [1]) from the surface of semiconductors [2,3], metals [4][5][6][7][8][9][10][11][12][13][14][15][16][17] or insulators [18]. Even though a large number of experimental and theoretical investigations on non-thermal desorption can be found in the literature, the present understanding of such light-induced reactions is still rather limited.…”