EXCITON AUTOIONATION IN ION INDUCED ELECTRON EMISSION

N. BAJALES; L. CRISTINA; S. MENDOZA; R.A. BARAGIOLA; E.C. GOLDBERG; J. FERRÓN

PHYSICAL REVIEW LETTERS

American Physical society

Año: 2008 vol. 100 p. 227604 - 227607

0031-9007

We report measurements of electron emission spectra from surfaces of Highly Oriented Pyrolytic Graphite (HOPG) excited by 1-5 keV He+ and Li+ which, for He+, exhibit a previously unreported high-energy structure.  Through a full quantum dynamic description that allows for the calculation of neutralization and electron-hole pair excitation processes, we show that these high-energy electrons can arise from autoionization of excitons formed by electron promotion to conduction band states close to the vacuum level. The same calculation shows no excitation of high-energy exciton for Li+ on HOPG, in agreement with the experimental absence of high energy electrons.