$L$ x rays from low-energy $(\sim 2-\mathrm{k}\mathrm{e}\mathrm{V}/\mathrm{u})$ ions with $L$-shell vacancies produced in single collisions with atoms and molecules

Intense L x rays have been observed in $\sim 2-\mathrm{k}\mathrm{e}\mathrm{V}/\mathrm{u}\hspace{0.5em}{\mathrm{Kr}}^{q+}$ $(q=27\mathrm{}–33)$ ions colliding with various atom and molecule targets. These x rays are understood to originate from electron capture processes into high-Rydberg states of the projectile ion from the outermost shell of target where the captured electron cascades down into the vacant L shell of the ion, thus emitting L x rays. It has been found that the observed L x-ray spectra move toward higher energy as the ion charge (q) increases. The observed L x-ray spectra are compared with synthetic spectra using various models. It has been found that the L x-ray production cross sections obtained for ${\mathrm{Kr}}^{27+}$ ions are inversely proportional to the ionization energy of target, similar to those recently observed in K x rays produced from ions with K-shell vacancy, and correspond to roughly 40% of total electron capture cross sections, meanwhile the rest of the electron cascades into the metastable states and thus cannot decay within a viewing region of a Si(Li) x-ray detector.