Date of Award

12-2012

Degree Name

Doctor of Philosophy

Department

Physics

First Advisor

Dr. John A. Tanis

Second Advisor

Dr. Thomas W. Gorczyca

Third Advisor

Dr. Asghar N. Kayani

Fourth Advisor

Dr. Murtadha A. Khakoo

Keywords

X-ray projectile emission, radiative electron single and double capture, photoionization, double photoionization, capture and ionization, coincidence measurements

Abstract

Radiative double electron capture (RDEC) is a one-step process in ion-atom collisions occurring when two target electrons are captured to a bound state of the projectile simultaneously with the emission of a single photon. The emitted photon has approximately double the energy of the photon emitted due to radiative electron capture (REC), which occurs when a target electron is captured to a projectile bound state with simultaneous emission of a photon. REC and RDEC can be treated as timereversed photoionization (PI) and double photoionization (DPI), respectively, if loosely-bound target electrons are captured. This concept can be formulated with the principle of detailed balance, in which the processes of our interest can be described in terms of their time-reversed ones. Fully-stripped ions were used as projectiles in the performed RDEC experiments, providing a recipient system free of electronrelated Coulomb fields. This allows the target electrons to be transferred without interaction with any of the projectile electrons, enabling accurate investigation of the electron-electron interaction in the vicinity of electromagnetic field.

In this dissertation, RDEC was investigated during the collision of fullystripped fluorine ions with a thin carbon foil and the results are compared with the recent experimental and theoretical studies. In the current work, x rays associated with projectile charge-changing by single and double electron capture and no charge change by F9+ ions were observed and compared with recent work for O8+ ions and with theory. Both the F9+ and O8+ ions had energies in the ~MeV/u range. REC, in turn, was investigated as a means to compare with the theoretical predictions of the RDEC/REC cross section ratio. The most significant background processes including various mechanisms of x-ray emission that may interfere with the energy region of interest are addressed in detail. This enables isolation of the contributions of REC and RDEC from the entire continuous spectrum of x-ray emission or at least ensures that the background processes have negligible contribution to the energy range of interest. Special emphasis is given to showing how the data analysis was carried out by the subtraction of the x rays due to contamination lines.

Comments

5th Advisor: Dr. Andrzej S. Warczak

Access Setting

Dissertation-Open Access

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Nuclear Commons

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