Singlet-to-triplet conversion of metastable He atoms at alkali-metal overlayers
- 15 April 1994
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 49 (15), 10607-10612
- https://doi.org/10.1103/physrevb.49.10607
Abstract
Energy distributions of electrons emitted from alkali-metal surfaces by impact of metastable He atoms reveal that there is a high probability for transformation of singlet atoms (excitation energy =20.6 eV) into triplet atoms (=19.8 eV) prior to deexcitation into the ground state. The conversion probability (as expressed by the ratio R of the intensities of valence-band emission due to triplet and singlet deexcitation, respectively) increases with increasing alkali-metal coverage on a Ru(0001) substrate, and in turn decreases with increasing oxygen exposure at a fixed alkali coverage. These findings indicate that R is a qualitative measure for the degree of ‘‘metallization’’ of the adlayer. R also increases with temperature due to broadening of the nearest-neighbor distribution whereby, on the average, a larger part of the adlayer becomes metalliclike. For Cs overlayers exhibiting work functions (12) formation as reflected by the R data as well as by the widths of the electron spectra.
Keywords
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