Disentangling the bulk and exit surface contribution on projectile-charge-state evolution

Abstract

Charge state evolution of the projectile ions while traversing through the solid target medium has been explored using the radiative electron capture process. The measured centroid energies of the convoluted radiative electron capture peak structures have been used to determine the mean K-shell binding energies and mean charge state of the projectile ions. It has been observed that the mean charge states of present measurements are lower than the earlier measurements done using the characteristic K α x-ray transitions. The difference is due to the capture of target electrons in the inner-shell vacancies, created during the collision process, of projectile ions. Further, the measured mean charge states are compared with the empirical predictions. A significant discrepancy between experimental and theoretical values has been observed, which is attributed to the multielectron capture by projectile ions due to nonradiative electron capture process from the exit surface while exiting from the foil. The significant variation between mean charge state values obtained from different tools provides a clear indication of the dynamic nature of the charge-changing mechanism at different regions (entrance surface, bulk, and exit surface) of the ion-solid interaction. The present results can be used to validate the departure between the theory and experiment on the charge state dependent stopping powers.

Theoretical studies on multiple ionization and electron capture processes in heavy ion induced M-shell ionization

“…The contrasting picture between incident charge state and q m inside the target is governed by the ion-solid interaction at the bulk of the target. While the q m for the outside the target is guided by the ion interaction with the solid surface [36][37][38]. In second step, the q m -values inside the target are substituted in the Lorentzian charge state distribution [38] to obtain the F(q) as follows…”

“…While the q m for the outside the target is guided by the ion interaction with the solid surface [36][37][38]. In second step, the q m -values inside the target are substituted in the Lorentzian charge state distribution [38] to obtain the F(q) as follows…”

Understanding the L-shell ionization mechanism through osmium atoms bombarded by 4-6 MeV/u fluorine ions

“…This feature has been described in detail by Chatterjee et al [20]. In the second part of the procedure, the q m values inside the target are substituted by a Lorentzian charge state distribution [49] to obtain the F (q) as follows…”

Exploring a novel model for projectile charge state distribution inside a solid-target

“…2(I). This contrasting picture is governed by the solid surface [2,9]. In second step, the q m -values inside the target are substituted in the Lorentzian charge state distribution [4] to obtain the F(q) as follows…”

“…Nevertheless, any direct measurement of the ionization phenomena inside the target was not possible until a couple of years ago [7] using the x-ray spectroscopy technique [8]. The charge state of the projectile ion (q) in the beam-foil plasma created due to ion-solid interactions [4] is considerably higher than the measured ionic state outside the target [9] because of electron capture phenomena from the exit surface [2]. Such an interesting feature has not yet been exploited in the foil stripper technology till date.…”