Multielectron InnerShell Photoexcitation in Absorption Spectra of Krypton: Theory and Experiment
Abstract
The probability of Kr 1s ionization alone and accompanied by excitation of a 4p, 3d, 3p, 2s, or a 2s and a 4p electron into bound or continuum states has been calculated for a photonenergy range extending a few hundred eV above the respective thresholds. The 1s ionization cross section was calculated relativistically including complete relaxation. Twoelectron photoexcitation and ionization was calculated with HartreeFock wave functions, except for transitions to (1sns) final states, for which DiracFock wave functions were employed. The calculations show that sharp features from twoelectron excitations are produced in an absorption spectrum only if at least one electron undergoes a transition to a bound state. For more tightly bound electrons, shakeoff tends to prevail increasingly over shakeup, whence double excitation features from innershell electrons become elusive. An absorptionspectrometry measurement was carried out with synchrotron radiation in order to test the calculations. Near the K edge of Kr, the measured absorption substantially exceeds the theoretical curve. For doubleelectron excitations, a backgroundsubtraction technique permitted analysis of the 1s3d and 1s3p cross sections as far as ~ 130 eV above threshold. The observed slow rise in doubleelectron absorption due to shakeoff processes in 1s3d and 1s3p transitions agrees rather well with theory. A model which parameterizes the transition from the adiabatic to the sudden approximation regimes compares favorably with the 1s3d and 1s3p cross sections. Threshold cross sections for 1s4p, 1s3d, and 1s3p transitions are poorly predicted by the singleconfiguration HartreeFock calculations. For 1s2s photoexcitation, only a very slight change in slope of the total absorption cross section is predicted at threshold, which would make it difficult to measure with presentday facilities. The data exhibit an apparent edge in the 1s2s excitation region which, however, agrees with theory neither in energy nor in magnitude and is most likely due to extraneous effects. With improvements in techniques and in synchrotronradiation sources, it may become possible in future to measure even these extreme innershell multielectron photoexcitation processes.
 Publication:

Ph.D. Thesis
 Pub Date:
 1991
 Bibcode:
 1991PhDT.......284S
 Keywords:

 KRYPTON;
 Physics: Atomic