Interaction delocalization in characteristic X-ray emission from light elements

Abstract Recently the first observation of channeling effect in oxygen K-shell X-ray emission was reported in this journal by Qian et al. [Ultramicroscopy 41 (1992) 147], who pointed out that this would allow oxygen to be used as a reference site in atom location by channelling enhanced microanalysis (ALCHEMI) applied to oxides. Experimental results for characteristic X-ray emission in spinel are reported which confirm their results. Calculations of ionization cross sections and the effective ionization potential for each of the constituent atoms of the spinel MgAl 2 O 4 have been carried out from first principles. This allows a quantitative theoretical insight into the channeling effect for the light elements Al, Mg and O which incorporates delocalization of the ionization interaction.