Alignment following Au L₃photoionization by synchrotron radiation

Abstract

The alignment of Au + ions following L 3 photoionization has been studied using a high-resolution x-ray spectrometer. We observed a small anisotropy for the angular dependence of Au L ι and Lα emissions. The alignment parameter A 20 derived from the experimental results is compared with theoretical calculations by Hartree-Fock approximation and random phase approximation with exchange. The contribution to the alignment of quadrupole interaction is discussed.

L-subshell fluorescence yields and Coster-Kronig transition probabilities with a reliable uncertainty budget for selected high- and medium-Zelements

“…They reported a maximum anisotropy of 5% of the Lα line with an instrumentation having a relative uncertainty of already 2% in the case of an isotropic emission characteristic. However, Yamaoka et al had also studied the angular distribution of Au L fluorescence lines following photoionization by monochromatized synchrotron radiation with energies in the vicinity of the L subshells [34,35]. They had found that in the case of the Au Ll fluorescence line an anisotropy of just a few percent might be possible, whereas the expected anisotropy of the Lα lines should be at least one order of magnitude lower, thus being somewhere in the per mille range which is not in line with some of the later findings [33] despite the undisputable fact that both works are based on the same theoretical considerations of Berezhko et al [36].…”

Coherence and correlations in photoinduced Auger and fluorescence cascades in atoms

“…Several groups published the results of measurements of the angular anisotropy of X-ray fluorescence, in which the 2p vacancies in heavy atoms have been created by radiation from radionuclides (see Santra et al, 2007 and references therein). Unusually large anisotropy as well as large forward-backward asymmetry have been reported in some of those experiments (see discussion in Yamaoka et al, 2002Yamaoka et al, , 2003Santra et al, 2007 and references therein) in drastic disagreement with the theoretical predictions. Recent, more precise and accurate measurements at SR sources, showed a very small anisotropy of L X-ray lines (Küst et al, 2003;Yamaoka et al, 2003Yamaoka et al, , 2006Barrea et al, 2005) in complete agreement with the theoretical predictions.…”

“…Unusually large anisotropy as well as large forward-backward asymmetry have been reported in some of those experiments (see discussion in Yamaoka et al, 2002Yamaoka et al, , 2003Santra et al, 2007 and references therein) in drastic disagreement with the theoretical predictions. Recent, more precise and accurate measurements at SR sources, showed a very small anisotropy of L X-ray lines (Küst et al, 2003;Yamaoka et al, 2003Yamaoka et al, , 2006Barrea et al, 2005) in complete agreement with the theoretical predictions. As it was suspected, the measurements with the radionuclides, which were interpreted as showing large alignment, contained some large systematic errors probably connected with self-absorption of the produced X-rays in the solid target.…”

“…A comprehensive list of references can be found in the papers by Yamaoka et al (2002) and by Kleiman and Lohmann (2003). Experimental values of the alignment are usually obtained from the angular distributions of Auger electrons (see, for example, Snell et al (2000) and references therein) or from the angular distribution and linear polarization of fluorescence (see, for example, Yamaoka et al, 2003). The orientation is experimentally determined from the circular polarization of fluorescence or spin-polarization of Auger electrons (Snell et al, , 1999a(Snell et al, , b, 2002Schmidtke et al, 2000aSchmidtke et al, , 2001.…”

Kinematic coefficient ratios, anisotropy parameters, and polarization degrees of L3 X-ray transitions of Bi, Pb, Ta, Lu, and Yb

“…Up to now, many experimental studies related with the angular distribution of the L 3 (J = 3/2) magnetic subshell X-ray transitions using different stimulating sources, such as synchrotron radiation [6][7][8], X-ray tube [9], radioisotope sources [10][11][12][13][14][15][16][17][18], and with charged particles [19][20][21][22][23][24] have been done.…”