Population of sputtered metastable silver atoms

Abstract

Neutral atoms released by ion induced sputtering of polycrystalline silver were investigated by resonant laser post-ionization and time-of-flight mass spectrometry. Two different resonant ionization schemes were employed to detect Ag atoms emitted either in the first metastable electronically excited state ( 4d 95s 2 2D 5 2 , excitation energy 3.75 eV) or in the ground state. From the saturation behavior of the photoionization process, the relative population of the metastable state with respect to the ground state was determined. A surprisingly high population of several percent is found which is interpreted in terms of the screening model.