PHOTODESORPTION AND WORK FUNCTION STUDY OF LONG-LIVING EXCITED ELECTRONIC STATES ON METAL-SURFACES

Excited electronic states in metals and in the near neighbourhood of m etal surfaces are commonly believed to have a very short lifetime, typ ically a femtosecond or even less. In the course of our photodesorptio n experiments we have found evidence of excited electronic states on a metal surface with a lifetime of about 30 fs. It was proved that this long-living electronic excitation is localized on surface structural defects. From our additional study on the photoelectric work function we can conclude that the surface structural defects have a fractional negative charge. The nature of the long-living excited electronic stat es and the desorption mechanism are discussed.