Transition Probabilities in the L Shell of Heavy Atoms.
Abstract
Measurements of L shell transition probabilities have been performed in response to a need for accurate experimental determination of fluorescence and CosterKronig yields. The scatter in literature data is significant, particularly for CosterKronig transition probabilities. Sophisticated relativistic selfconsistent field models of the atom have been developed, incorporating corrections for relaxation, radiative, and electronelectron correlation effects. With an accurate set of experimental data, the accuracy of theory can be established so that a complete and reliable set of data can then be calculated. A number of techniques, which were pioneered in earlier work in this field, are exploited. Of basic concern was the removal of experimental errors which became evident as techniques evolved. Particular attention was given to analytical modelling of spectra and efficiency calibration of solidstate detectors. A K xrayL xray coincidence technique is the primary means by which measurements were performed. Using radionuclide sources, the technique was used to evaluate the Coster Kronig transition probability f_{23 } and the fluorescence yields omega _2 and omega_3 for elements with Z = 78, 80, 81, 82, 92, and 94. In the region of Z = 80, predictions of DiracHartreeSlater theory were in excellent agreement with measured values of omega_2 and omega_3 but results indicated a consistent 5%10% overestimate of f_{23}. For Z >=q 92, the opposite situation arose whereby theoretical and experimental values for f_ {23} demonstrated reasonable agreement while theory had a tendency to overestimate omega _2 and omega_3. This coincidence approach was also adapted to provide further results of f_{23} for Z = 67 and 68 using gammaray fluorescence as a means of xray production; theory agreed quite well with these results. Methods for evaluating fluorescence and CosterKronig yields associated with all three L subshells were explored. One which involves accurate deconvolution of singles L xray spectra was tested, with promising results, using a ^{210}Pb source. A second method was an L conversion electronL xray coincidence technique which requires the use of an electron spectrometer. Investigation led to the conclusion that a modified version of a particular design of electrostatic analyzer would provide a feasible means of accomplishing such measurements.
 Publication:

Ph.D. Thesis
 Pub Date:
 1989
 Bibcode:
 1989PhDT........67M
 Keywords:

 Physics: Atomic