Chemically Induced Electronic Excitations at Metal Surfaces
Brian Gergen,1
Hermann Nienhaus,2
W. Henry Weinberg,13
Eric W. McFarland1*
The energy released in low-energy chemisorption or physisorption of
molecules on metal surfaces is usually expected to be dissipated by
surface vibrations (phonons). Theoretical descriptions of
competing electronic excitations are incomplete, and experimental observation of excited charge carriers has been difficult except at
energies high enough to eject electrons from the surface. We observed
reaction-induced electron excitations during gas interactions with
polycrystalline silver for a variety of species with adsorption energies between 0.2 and 3.5 electron volts. The probability of exciting a detectable electron increases with increasing adsorption energy, and the measured time dependence of the electron current can be
understood in terms of the strength and mechanism of adsorption.
1 Department of Chemical Engineering,
University of California, Santa Barbara, CA 93106-5080, USA.
2 Laboratorium für Festkörperphysik,
Gerhard-Mercator-Universität, 47048 Duisburg, Germany.
3 Symyx Technologies, 3100 Central Expressway, Santa
Clara, CA 95051, USA.
*
To whom correspondence should be addressed. E-mail:
mcfar{at}engineering.ucsb.edu
