Vibrationally promoted electron emission from low work-function metal surfaces
Abstract
We observe electron emission when vibrationally excited NO molecules with vibrational state v, in the range of 9⩽v⩽18, are scattered from a Cs-dosed Au surface. The quantum efficiency increases strongly with v, increasing up to 10-2 electrons per NO (v) collision, a value several orders of magnitude larger than that observed in experiments with similar molecules in the ground vibrational state. The electron emission signal, as a function of v, has a threshold where the vibrational excitation energy slightly exceeds the surface work function. This threshold behavior strongly suggests that we are observing the direct conversion of NO vibrational energy into electron kinetic energy. Several potential mechanisms for the observed electron emission are explored, including (1) vibrational autodetachment, (2) an Auger-type two-electron process, and (3) vibrationally promoted dissociation. The results of this work provide direct evidence for nonadiabatic energy-transfer events associated with large amplitude vibrational motion at metal surfaces.
- Publication:
-
Journal of Chemical Physics
- Pub Date:
- February 2006
- DOI:
- 10.1063/1.2166360
- Bibcode:
- 2006JChPh.124f4702W
- Keywords:
-
- 79.20.Rf;
- 34.50.Dy;
- 73.30.+y;
- 82.65.+r;
- Atomic molecular and ion beam impact and interactions with surfaces;
- Interactions of atoms and molecules with surfaces;
- photon and electron emission;
- neutralization of ions;
- Surface double layers Schottky barriers and work functions;
- Surface and interface chemistry;
- heterogeneous catalysis at surfaces