Determination of some atomic parameters related to XRF and their applications

Abstract

The work presented in this thesis deals with the determination of some atomic parameters related to X-Ray Fluorescence (XRF) and their applications. newlineX-ray fluorescence is the phenomenon of emission of X-rays as a result of decay of atomic inner shell vacancy created by a bombarding photon of energy greater than the binding energy of the shell electron. The process of photon induced vacancy creation is called photoionization/photoexcitation. The decay of vacancy takes place by the jump of an outer shell electron and the process is called de-excitation that results in fluorescent Xray/ Auger electron emission. The investigations of emitted radiation lead to the exploration of the processes by which the atomic inner shell vacancy is created and filled up. For shells involving a number of sub-shells like L, M and higher shells, there are Coster-Kronig/Super Coster-Kronig transitions occurring before the decay of vacancy by outer shell electron jump. Coster-Kronig transition is the shift of the vacancy in ith subshell to some upper jth sub-shell within the same shell and the energy difference of two involved sub-shells knocks out an outer shell electron. Thus, no X-rays are emitted and atom gets doubly ionized. When the initial vacancy leads to two vacancies in the subshells of same shell, it is called super Coster Kronig transition (Bambynek et al., 1972). The process of creation and filling of vacancies involve various fundamental atomic parameters i.e. photoionization cross-section, fluorescence yield, Coster-Kronig transition probabilities, fractional decay rates etc. In the presence of magnetic field, electron having total angular momentum quantum number j possesses 2j+1 magnetic sub-states mj varying from mj to +mj as projections of j in the magnetic field direction. In an excitation, the number of created vacancies may vary in different magnetic sub-states of a state with jgt1/2, which leads to vacancy alignment (Berezkho and Kabachni k, 1977;Berezkho et al., 1978) and is quantized as alignment parameter, A.