Date of Award
Doctor of Philosophy
Dr. John A. Tanis
Dr. Asghar N. Kayani
Dr. Thomas W. Gorczyca
Dr. Andrzej S. Warczak
Radiative double electron capture (RDEC) by highly-stripped ions in collisions with atomic targets is a fundamental process that can be used to study electron-electron correlation, the interaction between two electrons, in the vicinity of the Coulomb field of a bare ion. In this process two electrons from the target are captured to bound states of the projectile with the simultaneous emission of a single photon. RDEC is closely related to the well-known one-step atomic process of radiative electron capture (REC), in which a target electron is captured to the projectile and a photon is simultaneously emitted. REC and RDEC can be considered as the inverse processes of single and double photoionization, respectively, when the binding energy of the captured electron in the target is small compared to the kinetic energy of the electron measured in the projectile reference frame.
RDEC was first observed for fully-stripped oxygen ions in collisions with a thin-foil carbon target. The cross sections found for RDEC in that work were about an order of magnitude greater than the values expected from recent theoretical predictions. Investigation of RDEC for solid targets is complicated due to multiple collisions inside the foil, which often yields detection of a charge-changed projectile ion different from the one involved in the RDEC process.
In this study, RDEC for fully-stripped fluorine ions (F9+) in collisions with a molecular nitrogen gas target is investigated and compared with the previous experimental measurements for the foil target and with theoretical predictions. The gas target enables studying the process 3 under single collision conditions. Also, gas targets are contaminant free compared to the solid target. RDEC for one-electron F8+ ions is also investigated and compared with the results for the fully-stripped ions. The REC data obtained in this work are analyzed and compared with theory and subsequently used to obtain the RDEC to REC cross section ratios for comparison with theory.
Kumara, Nuwan Sisira, "Radiative Double Electron Capture (RDEC) by Fully-Stripped Fluorine Ions in Collisions with Nitrogen" (2018). Dissertations. 3365.