Electronic energy loss at zero atomic impact parameter: its importance for the Lewis effect and narrow nuclear resonance depth profiling

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 108; no. 4; pp. 403 - 407
• Main Authors: Vickridge, I.C., Amsel, G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.1996
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/0168-583X(95)01163-3

We describe a simple way to include in analytic calculations of the shapes of excitation curves obtained in the vicinity of narrow nuclear resonances, the effect of the electronic energy loss suffered by the charged particle during the nuclear encounter, which occurs by definition with an atomic impact parameter of zero. A simple expression is given for estimating the reduction in magnitude of the Lewis effect due to zero-impact-parameter ionisation losses. Observed effects are expected to be greatest for nuclear interactions at low energies such as for the 21Ne(p, γ) resonance at 272 keV and the 29Si(p, γ) resonance at 324 keV, but it is shown that such losses may even have a measurable but previously unrecognised influence on the Lewis effect observed via the 27Al(p, γ) resonance at 992 keV in pure Al. Finally, a robust deconvolution method is presented for removing the effect of zero-impact-parameter ionisation losses from experimental measurements of nuclear resonance excitation curves, such as are made in resonance depth profiling.