Experimental determination of atomic alignment of Mo42, Cd48 , and In49 with differential x-ray intensity ratios by 100–250-keV proton impact

Abstract

This work aims to study the alignment properties of electron vacancies produced by proton bombardment in the low-energy region from 100 to 250 keV. The alignment parameter ${\mathcal{A}}_{20}$ of $_{42}\mathrm{Mo}, _{48}\mathrm{Cd}$, and $_{49}\mathrm{In}$ ions after ${L}_{3}$ subshell ionization has been investigated experimentally. The typical $L$ x-ray spectra are measured for each target at emission angles from ${115}^{\ensuremath{\circ}}$ to ${155}^{\ensuremath{\circ}}$. The angular dependence of differential intensity ratios ${L}_{\ensuremath{\alpha}}/{L}_{\ensuremath{\beta}1}$ and ${L}_{\ensuremath{\beta}2}/{L}_{\ensuremath{\beta}1}$ is studied as a function of the second-order Legendre polynomial ${P}_{2}(\mathrm{cos}\ensuremath{\theta}$). Our result demonstrates that ${L}_{\ensuremath{\alpha}}$ and ${L}_{\ensuremath{\beta}2}$ lines exhibit anisotropic emission spatially. The anisotropy parameter is converted to the alignment parameter by considering the Coster-Kronig (CK) correction coefficient and anisotropy coefficient. The results are compared with theoretical prediction within the framework of the semiclassical theory of inner-shell ionization, and good agreement is found in general. A small discrepancy around the inflection point of the alignment parameter is attributed to the atomic parameters employed only for single ionization in the CK correction coefficient.