Natural widths and Coster Kronig transitions of L X-ray spectra in elements between Pd and Sb

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1 Radiation Physics and Chemistry 75 (26) Natural widths and Coster Kronig transitions of L X-ray spectra in elements between Pd and Sb Shusuke Sakakura a,, Hirofumi Oohashi a, Yoshiaki Ito a, Tatsunori Tochio b, Aurel M. Vlaicu c, Hideki Yoshikawa c, Eiji Ikenaga d, Keisuke Kobayashi d a Laboratory of Atomic & Molecular Physics, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611, Japan b Keihanna Interaction Plaza Inc., 1-7 Seika-cho, Soraku-gun, Kyoto , Japan c National Institute of Material Science, SPring-8, Mikazuki, Hyogo , Japan d Japan Synchrotron Radiation Research Institute (JASRI), Kouto, Mikazuki-cho, Sayo-gun, Hyogo , Japan Accepted 27 July 25 Abstract The La and Lb X-ray emission spectra in the elements between Pd (Z ¼ ) and Sb (Z ¼ ) were measured using a high-resolution double-crystal vacuum spectrometer. The relative intensities of satellite structures, which originate in L 1 L 3 M 4,5 Coster Kronig transitions, were estimated to that of each diagram line, and compared with calculated values. According to the work of Chen et al. [1977a. Theoretical L-shell Coster Kronig energies 11pZp13. At. Data Nucl. Data Tables 19, 97 1], Salgueiro et al. [1987. J. Phys. (Paris) 48 Colloq. C9, 69] and Vlaicu et al. [1998. Investigation of the 74W L emission spectra and satellites. Phys. Rev. A 58, 3544] L 1 L 3 M 4 Coster Kronig transition is forbidden for 5pZp77, and L 1 L 3 M 5 Coster Kronig transition is forbidden for 5pZp73. The results suggest that L 1 L 3 M 4,5 Coster Kronig transitions may be allowed even for Sn (Z ¼ 5) and Sb (Z ¼ ). r 26 Elsevier Ltd. All rights reserved. PACS: 32.3.Rj; 32.8.Hd Keywords: Natural width; Coster Kronig transition; Satellite structure 1. Introduction X-ray spectra have usually the satellites attributable to multiple vacancies. Two different processes are considered for the origin of them: one is the shake process and the other is nonradiative process such as Coster Kronig transition. Recently, Coster Kroing transitions have been studied theoretically and experimentally. Yin et al. (1973) reported for Cu and Zn L 2 level widths wider than the Corresponding author. address: caligula@scl.kyoto-u.ac.jp (S. Sakakura). L 3 level width due to the L 2 L 3 M 4,5 Coster Kronig transitions. The ratio of the satellites to the Lb 1 X-ray emission intensity using 2.5 MeV proton bombardment showed a sharp drop at Zr and concluded this drop is attributed to the closing of L 1 L 2 M 4,5 Coster Kronig channel (Doyle et al., 1979). Hague et al. (198) measured the La X-ray emission spectra of Ag below and above the L 1 ionisation energy by electron bombardment, and concluded that the La 1 line becomes.13 ev narrower and the fine structure disappeared when measured below the L 1 ionisation energy due to L 1 L 3 M 4,5 Coster Kronig transitions. It is generally accepted that L 1 L 3 M 4 Coster Kronig transition was X/$ - see front matter r 26 Elsevier Ltd. All rights reserved. doi:1.116/j.radphyschem

2 1478 S. Sakakura et al. / Radiation Physics and Chemistry 75 (26) forbidden for 5pZp77, L 1 L 3 M 5 Coster Kronig transition was forbidden for 5pZp74 energetically (Chen et al., 1977a). However, Salguiro et al. (1987) and Vlaicu et al. (1998) observed the satellites in the high-energy region of Lb 2 of W (Z ¼ 74) and concluded that this arise due to L 1 L 3 M 5 Coster Kronig transition. In this work, we investigated the linewidths and intensities of the La and Lb X-ray emission spectra in the elements between Pd (Z ¼ ) and Sb (Z ¼ ) in order to confirm L 1 L 3 M 4,5 Coster Kronig transition in these elements. 2. Experiment Each emission spectra was measured using highresolution double-crystal vacuum spectrometer (Rigaku System 358EKI). A rhodium target was used as a primary tube and operated at excitation voltage of 4 kv and tube current of 7 ma. The spectrometer has a pair of Ge (1 1 1) crystal [2d ¼ nm]. The samples of Pd, Ag, Cd, In and Sn were pure metal sheets, and the sample of Sb a pure metal block. The detector was Ar.9 (CH 4 ).1 gas flow proportional counter (FPC). Measuring periods were set to take around 1, counts at the peak position of the La 1 and the Lb diagram. 3. Results 3.1. Correction of linewidths For double-crystal spectromter, the instrumental function is usually considered to be very small, so we can neglect it. But, in order to get true linewidth the proper correction is still needed. Brogren (1954, 1963) estimated the true linewidth using the following formula: W T ¼ W o W C, (1) where W T, W o, and W C is the true linewidth, the width of the observed emission line and the width of the rocking curve. But Tochio et al. (22) showed that, by this correction, the crystal dispersion was overestimated and the estimated linewidth is smaller than the true linewidth, so they suggested another reliable correction for the double-crystal spectrometer. Tochio s correction method is following. For double-crystal spectrometer, the glancing angle of the radiation for the first cystal and the second crystal, denoted by Z 1 and Z 2, are Z 1 ¼ Zðy; jþ ¼ p arccosðcos j sin yþ, (2) 2 Z 2 ¼ Zð2b y; jþ ¼ p arccos cos j sinð2b yþ, 2 (3) where y is the angle between the projection of the radiation on the horizontal plane and the crystal plane for reflection, j is the angle between the radiation and the horizontal plane, and b is Bragg angle. The dependence of the intensity, the slit function and the rocking curve for the radiation having the energy are F(E), S(j) and R(E, j) respectively, and the intensity with the crystal positions at Bragg angle b, I(E, b) is IðE; bþ ¼ Z 1 Z j Z p=1 j RðE; Z 2 ÞdE d j dy, FðEÞSðjÞRðE; Z 1 Þ where S(j) can be given by triangle function, and when crystals are perfect, R(E, j) can be calculated on the basis of dynamical theory (Zachariasen, 1945) with the effect of absorption described by Zachariasen. By Eq. (4), we can calculate the distribution of the instrumental function Numerical calculation of the relative intensity Chen et al. (1977b) have calculated using a Hartree Fock Slater potential model to conclude that an extra hole in the M shell shifts the La 1 diagram line of Ag by over 9 ev and Lb 2.15 diagram line of Ag by over 3 ev. So an extra hole in the M shell causes visible satellites. We can calculate the relative intensity of the visible satellites to the diagram line according to procedures described below. The initial L i hole population, the shakeoff probability of L i and the L i L j X Coster Kronig yield are given by N i, P i and f ij, respectively. To separate the LM and LN double-hole states, the shakeoff probabilities and Coster Kronig yields are P i ¼ P im þ P in, (5) f ij ¼ f ijm þ f ijn, (6) where P ix is the X-shell shakeoff probability during L i shell ionization and f ijx is the L i L j X Coster Kronig yield. The number of L 3 hole states left after Coster Kronig transition is n 3 ðl 3 Þ¼ð1 P 3 ÞN 3. (7) The number of LM-hole states is n 3 ðl 3 MÞ¼N 3 P 3M þ N 1 ð1 P 1M Þf 13M (8) and the number of LN-hole states is n 3 ðl 3 NÞ¼N 3 P 3N þ N 1 ð1 P 1M Þf 13N þ N 1 ð1 P 1M Þf 12N f 23N þ N 2 ð1 P 2M Þf 23N. We cannot separate the hidden satellites which are caused by LN-hole states in the observed diagram line, ð4þ ð9þ

3 S. Sakakura et al. / Radiation Physics and Chemistry 75 (26) FWHM [ev] so the apparent diagram line intensity is RðL 3 YÞ I M ¼ n 3 ðl 3 Þþn 3 ðl 3 NÞ, (1) T where R(L 3 Y) is the L 3 Y radiative transition probability and T is the total transition probability. LM-hole states, the visible satellites the intensity due to the LM-hole is I S ¼ n 3 ðl 3 MÞ RðL 3YÞ. (11) T 2.4 Therefore the relative intensitiy of the satellites to the diagram line is I S n 3 ðl 3 MÞ ¼ I M n 3 ðl 3 Þþn 3 ðl 3 NÞ. (12) Thus we can caluculate the relative intensity numerically Curve fitting FWHM [ev] Fig. 1. Linewidths of this work, other experimental widths (Juslen et al., 1979; Hague et al., 198; Parratt, 1938; Putila et al., 1984; Ohno et al., 1984) and the natural widths calculated from Campbell work for La 1 (upper) and Lb 2,15 (lower). Table 1 Ag La 1 widths Ge(1 1 1) Si(1 1 1) XPS La 1 for Ge(1 1 1), La 1 for Si(1 1 1) and La 1 natural width calculated from XPS L 3 level width and M 5 level width. 5 The instrumental function of the double-crystal spectrometer with an anti-parallel setting is so small that the measured spectra can be approximated to Lorenz function. The measured spectra were fitted to Lorenz functions by the least-square method and we got the linewidths and intensities of each spectrum. La 1 and La 2 in each La spectrum were fitted to one Lorenz function, respectively, and visible satellites were fitted to two Lorenz functions, and Lb 2,15 to one Lorenz function and the visible satellites to three Lorenz functions in Lb 2, Linewidths The linewidths which were corrected by Tochio s method are shown in Fig. 1. For a comparison, other experimental widths and the widths calculated from Campbell et al. (21) are given in Fig. 1. The widths in the present work are wider than other experimental widths. This is because in other experiment the widths corrected by Eq. (1), the crystal dispersion was considered to be overestimated, therefore they are too small. Measured Fitting Ag L3 edge Lβ2,15 47 Ag 5 Sn Sn L3 edge RELATIVE ENERGY [ev] 1 2 Fig. 2. Observed spectra and results of fitting of Lb 2,15 in Ag (left)and Sn (right).

4 148 S. Sakakura et al. / Radiation Physics and Chemistry 75 (26) INTENSITY (ar arb. unit its) Lα 1,2 Pd 47 Ag 48 Cd 49 In 5 Sn Sb Lα 2 (L 3 M 4 ) Lα 1 (L 3 M 5 ) 1 Satellite RELATIVE ENERGY [ev] 2 Fig. 3. La 1 spectra. For Sn and Sb, visible satellites become weak La 1 The line widths of this work and the widths reported show same tendency in the La 1 spectra. Three values of La 1 width are shown in Table 1. The widths of the La 1 spectra were measured using different crystals, Ge(1 1 1) and Si(1 1 1), and in XPS. L 3 level width in Ag used 2.1 ev which was measured with XPS at BL29XU in SPring-8. The value of.4 ev was used for the M 5 level width reported by Yin et al. (1973). The width for Ge(1 1 1) is larger than the width for Si(1 1 1) due to the crystallinity and the dispersion. Moreover, it is possible that the natural width is nearly equal to the width in XPS but the hidden satellites may affect the observed widths. Is/Im [%] Lα Lβ2 Calc Lb 2,15 Lb 2,15 spectra of Pd was affected greatly by selfabsorption (Pd L 3 edge: 3173 ev) and abrupt change of detector s efficiency at Ar K edge (Ar K edge: ev). Therefore the analysis was very difficult (Fig. 2). The hidden satellites were near the peak and the peak shaped asymmetric Lorenz function and have the long tail in the higher energy side. As Z number is higher, the hidden satellite shifted larger. At high Z, asresultofcurvefitting, the hidden satellites can be separated from the diagram line appropriately, they becomes the visible satellites Relative intensity La 1 spectra are shown in Fig. 3. The visible satellites due to LM-hole states abruptly become weak around Sn Fig. 4. Relative intensities of visible satellites to the diagram line. and Sb elements. This state can be considered to be created by Coster Kronig transition and by the shake process. The relative intensities of the satellites to the La 1 and Lb 2,15 spectra as a result of fitting and theoretical relative intensities are shown in Fig. 4. In Sn and Sb elements the theoretical relative intensities are calculated according to the work of Chen et al. (1977a). But the relative intensities in Sn and Sb are bigger than the theoretical relative intensities. The results show that 52

5 S. Sakakura et al. / Radiation Physics and Chemistry 75 (26) L 1 L 3 M 4,5 Coster Kronig transitions can be allowed even at Sn and Sb. 4. Conclusion We measured the La 1 and Lb 2,15 spectra. The observed linewidths are wider than the reported ones in these elements. The reason for the discrepancy between the experiment and theory may be due to the hidden satellites. Moreover, although L 1 L 3 M 4,5 Coster Kronig transitions are forbidden in Sn according to Chen et al. (1977a) it is found that L 1 L 3 M 4,5 Coster Kronig transitions can be allowed even at Sn and Sb. Acknowledgments This work was performed under collaboration of Regional Entities for the Advancement of Technological Excellence, JST, and was been performed under the approval of the Spring-8 Program Advisory Committee (Proposal No. 24B653-Nxa-np ¼ Na). The measurement of XPS was carried out at BL29XU, Spring-8. References Brogren, G., Ark. Fys. 8, 391. Brogren, G., Ark. Fys. 23, 219. Campbell, J.L., et al., 21. Widths of the atomic K N7 Levels. At. Data Nucl. Data Tables 77, Chen, M.H., et al., 1977a. Theoretical L-shell Coster Kronig energies 11pZp13. At. Data Nucl. Data Tables 19, Chen, M.H., et al., 1977b. Interpretation of the silver L X-ray spectrum. Phys. Rev. A 15, Doyle, B.L., et al., L 1 -L 2,3 M 4,5 Coster Kronig transition thresholds in the region 37pZp56. Phys. Rev. A 19, Hague, C.F., et al., 198. High-resolution electron-excited Ag La emission spectra below and above the L 1 ionisation threshold. Phys. Lett. A 78, Juslen, H., et al., La X-ray spectra of elements between 4Zr and 48 Cd. Phys. Rev. A 19, Ohno, M., et al., L X-ray linewidths of the elements Nb to Sb. II. J. Phys. B 17, Parratt, L.G., The silver L series X-ray spectrum: line widths, wave-lengths, relative intensities, satellites, and widths of energy levels. Phys. Rev. 54, Putila, P., et al., L X-ray linewidths of the elements Nb to Sb. I. J. Phys. B 17, Salguiro, L., et al., J. Phys. (Paris). 48 Colloq. C9, 69. Tochio, T., et al., 22. Broadening of the X-ray emission line due to the instrumental function of the double-crystal spectrometer. Phys. Rev. A 65, Vlaicu, A.M., et al., Investigation of the 74W L emission spectra and satellites. Phys. Rev. A 58, Yin, L.I., et al., Width of atomic L 2 and L 3 vacancy states near Z ¼ 3. Phys. Rev. A 7, Zachariasen, W.H., Theory of X-ray Diffraction in Crystals. Wiley, New York.

Investigation of the 74 W L emission spectra and satellites

PHYSICAL REVIEW A VOLUME 58, NUMBER 5 NOVEMBER 1998 Investigation of the 74 W L emission spectra and satellites Aurel-Mihai Vlaicu,* Tatsunori Tochio, Takashi Ishizuka, Daisuke Ohsawa, Yoshiaki Ito, and