Vacancy configurations of argon projectile ions in solids

The use of high-resolution x-ray measurements in determining the electronic vacancy configuration of an energetic ion inside a solid has been applied to 4.0- and 5.0-MeV Ar projectiles incident on a KCl target. The Ar $K{\alpha }_{1,2}$ line is found to be shifted to higher energies by 6.1 ± 0.6 and 8.1 ± 0.6 eV, respectively, at these bombarding energies. These shifts correspond to five and six vacancies in the Ar $3s-3p$ subshells. The Cl $K{\alpha }_{1,2}$ line is used as a reference line and thin-target x-ray cross-section measurements are used to show that Cl and Ar are excited in the same manner.