Study of processes following L and M shell photoionization using EDXRF technique and analytical application

Abstract

The present thesis pertains to study of physical parameters characterizing the processes following L and M shell photoionization. The investigations involve study of the Li(i=1-3) sub-shell X-ray production (XRP) cross-sections and fluorescence yields for some rare-earth elements, the Mi(i=1-5) sub-shell XRP cross-sections and fluorescence and Coster-Kronig yields for heavy elements. As an application of the EDXRF technique the soil and vegetation (maize crop) samples were analyzed for major and trace elements in order to study the affect of the herbicide. The processes following atomic inner-shell photoionization are described by different physical parameters, namely, the photoionization cross-sections, X-ray, Auger and Coster-Kronig transition rates, Fluorescence and Coster-Kronig yields and vacancy transfer probabilities. These parameters are also required to calculate the Li(i=1-3) and Mi(i=1-5) sub-shell X-ray production cross-sections (XRP), which in turn, are required for different applications. The current status of these physical parameters has been presented in the Chapter 1. The energy dispersive X-ray fluorescence (EDXRF) spectrometer available at RRCAT, Indore was used for the present work. It involves a sealed annular source of 109Cd (25mCi) procured from Eckert and Ziegler, Isotope Products, France, and a Si(Li) detector (Eurisys-CANBERRA-SL12155, 12.5mm2×2mm; energy resolution ~155eV at 5.9 keV, Be window 0.025mm thick) coupled to PC based multichannel analyzer through a spectroscopy amplifier. The details of excitation source, X-ray detector and PC based multichannel analyzer are given in Chapter 2. The photo peak efficiency of the Si(Li) detector in the annular source geometry over the energy region 3-17 keV was determined by measuring the K X-ray yields from the elemental targets of TiO2 K2Cr2O7, MnO2, Co(NO3)2 .6H2O, NiCl2 .6H2O, CuO, ZnSO4.7H2O, As2O3, Se, SrCO3, MoO3 and from knowledge of K X-ray fluorescence cross-sections. The details of evaluation procedures are given in this chapter.