Radiative electron capture by bare and H-like Si and Cl ions using the channeling technique and the associated solid-state effect.

Abstract

Fully stripped and hydrogenlike Si and Cl ions, in the energy range 2--5 MeV/amu and channeled through a 0.17 \ensuremath{\mu}m thick Si single crystal, were used to study the radiative electron capture (REC) into the K shell of the ions. The associated effects due to the solid medium of the target were also investigated from the energy and the derived cross section of the REC photons. The K-shell REC cross sections were found to fall on a universal curve when plotted against the adiabaticity parameter of the collision system. The measured energy shifts in the REC photon energy and the higher yield of REC photons using crystalline targets, as compared to the available gas-target data, are indicative of an ``ion--solid-state effect'' caused by the electron-wake potential. The magnitude of these effects is shown to increase with Z/v of an ion with charge Z and velocity v, and are in qualitative agreement with recent calculations. The REC cross sections are, however, observed to be slightly smaller than the theoretical estimates after taking into account the effects associated with the solid medium. The widths of the REC peaks are compared with the theoretical models. The results of the present investigation using Si and Cl ions are presented coherently along with our earlier data using lighter ions.