USE OF SPIN-LABELING TECHNIQUES TO STUDY THE DYNAMICS OF SURFACE PENNING IONIZATION

Spin labeling techniques, specifically the use of electron-spin-polarized He(2 3S) metastable atoms coupled with energy-resolved spin analysis of the ejected electrons, are used to investigate the dynamics of metastable atom deexcitation by molecules in a film several monolayers thick condensed on a cooled Cu(100) surface. Data for CO2, H2O, Cl2, and O2 films show that metastable deexcitation is analogous to gas-phase Penning ionization, i.e., the condensed molecules can be considered as a "solid gas." Detailed differences are, however, evident that can be attributed to the presence of neighboring molecules. Data for C60 films are also presented which suggest the possibility of plasmon excitation as is observed in photoionization and electron energy loss data.