On the kinetic energies of sputtered excited particles: II. Theory and applications to group IIA fluorides

Abstract

The light intensity emitted from sputtered excited states (atoms or ions) is readily measured as a function of perpendicular distance from the target and this has led to numerous attempts to gain information on the kinetic energies of the emitting species. In the present work we examine both atoms and ions in excited states and, moreover, explore four categories of mathematical analysis differing mainly in what is assumed for P(E), the probability of a sputtered species with kinetic energy E being found in a particular excited state. The assumptions for P(E) are these: (i) a step function with the step at E = E∗, (ii) what is effectively the combination of a step at E = E∗ with P(E) α E1/2, (iii) the combination of a step at E = E∗ with P(E) ∝ (E −E∗)1/2, (iv) an E-independent constant, with the distribution of sputtered energies taken as E(E + E∗)−3. Considering 6 different MgI, CaI, SrI, and BaI lines and 7 different MgII, CaII, SrII, and Ball lines, we obtain characteristic energies, E∗, lying mainly in the interval 102−103 eV independently of whether we are dealing with atoms or ions or of what is assumed for P(E). It is concluded that, by virtue of the characteristic energies being so high, as well as for other reasons such as size, ions and excited states (themselves atoms or ions) have different origins. © 1980, All rights reserved.