The quantitative characterization of liquid and solid surfaces with metastable helium atoms

The electron spectroscopy based on the excitation energy of metastable rare gas atoms is a valuable tool for surface analysis because its surface sensitivity does not depend on the limited mean free path of the emitted electrons in condensed matter, but is perfect due to the physics of the emission process. Up to recently, the application of the method has suffered from the fact that a quantitative evaluation of the measured spectra has not been possible. The present contribution describes some progress in this respect which has been made during the last few years.