Electronic energy transfer on CaO surfaces.
We excite low-coordinated surface sites of nanostructured CaO samples using tunable UV laser pulses and observe hyperthermal O-atom emission indicative of an electronic excited-state desorption mechanism. The O-atom yield increases dramatically with photon energy, between 3.75 and 5.4 eV, below the bulk absorption threshold. The peak of the kinetic energy distribution does not increase with photon energy in the range from 3.9 to 5.15 eV. These results are analyzed in the context of a laser desorption model developed previously for nanostructured MgO samples. The data are consistent with desorption induced by exciton localization at corner-hole trapped surface sites following electronic energy transfer from higher coordinated surface sites.
Joly
Alan G
AG
Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA.
Beck
Kenneth M
KM
Hess
Wayne P
WP