De-excitation of Metastable Atoms and Ions on Metal Surfaces

Abstract

The de-excitation of a metastable atom follows either a collision of the first kind (in which the metastable atom undergoes a transition into a higher energy level, after which it goes to the ground state by emission of radiation) or collisions of the second kind (in which the excitation energy is transmitted to the particle with which it collides and may cause the ejection of secondary electrons). The secondary electrons emitted in collision processes of the second kind may in turn result from two different processes. In one process the metastable atom will be converted into an ion (resonance ionization, Section 12.1) and then undergo Auger neutralization with electron emission (Section 12.1, Fig. 12.1.a, curve γ). In another process the metastable atom will undergo Auger de-excitation—also with electron emission (Section 12.1, Fig. 12.1.a, curve β).