The Influence of Channeling on the Shape and Intensity of Doppler-Broadened Spectral Lines Produced by Light Ion Bombardment of Metals

Abstract

An interesting consequence of the bombardment of solids by ions or atoms with keV energy is the visible light emitted by the backscattered particles. The observed spectral lines are broadened in a manner consistent with Doppler shifting of the radiation, which arises because the backscattered atoms possess a distribution of energies and directions with respect to the detector. Here we report on calculations of the shape of the Doppler-shifted Balmer β-line and comparison with experimental results for proton bombardment of a Cu target in the energy region from 5 – 100 keV.

In this calculation three independent parameters must be considered:

• the energy distribution of backscattered projectiles,

• the energy dependence on the neutralization probability in an excited state upon emerging from the Cu surface,

• the probability for non-radiative decay via an interaction with the metal surface.

It will be shown how the use of the channeling phenomenon in monocrystalline Cu helps verifying the relative importance of these three parameters on the actual shape and intensity of the spectral lines.