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采用中心能量为13.1 keV (最大能量小于30 keV)的轫致辐射光子碰撞Au靶, 在130°—170°的探测角度范围内以10°为间隔, 测量了碰撞产生的特征X射线Lι, Lα, Lβ和Lγ1的光谱. 根据实验测得的能谱结果, 综合考虑探测器的探测效率及靶材的吸收校准后, 计算了不同探测角度下特征X射线Lα与Lγ1及Lι与Lγ1的相对强度比; 而且, 还基于不同探测角度下X射线强度比值, 分析了特征X射线的角分布情况. 实验结果表明特征X射线Lα和Lι为各向异性发射. 此外, 计算了特征X射线Lι的各向异性参数为0.25, 并据此推断出L3支壳层的定向度A20为0.577 ± 0.081; 分析认为L3支壳层的定向度A20由该支壳层本身的物理特性决定, 但该支壳层的各向异性参数β会受到Coster-Kronig跃迁的影响而发生改变.
The vacancy can be produced through impact ionization of target atom by energetic particles. It is of significant importance to study the vacancy state by the measurement of angular distribution of typical X-rays. At present, accurate ionization cross-section data of the atomic inner shell are urgently required in many areas. However, the precise measurement of ionization cross-section of the atomic inner shell is largely dependent on the fact that whether the characteristic radiation (e.g., X-ray) is isotropic. In this experiment, the characteristic Lι, Lα, Lβ and Lγ1 X-rays for Au target are measured by a silicon drift detector in an emission angle range from 130° to 170° in steps of 10°. A mini-X ray source is utilized to produce bremsstrahlung with the center energy of 13.1 keV. Considering detection efficiency of the detector and the absorption of the target, relative intensity ratios, I(Lα)/I(Lγ1) and I(Lι)/I(Lγ1), are obtained at different detection angles based on the experimental energy spectrum results. Moreover, the angular dependence of X-ray intensity ratio is investigated and it is found that the X-rays Lι and Lα exhibit anisotropic emission. According to the X-ray intensity ratio I(Lι)/I(Lγ1) and the P2(cosθ), and using the least square method, the anisotropic parameter β of characteristic X-ray Lι is derived to be 0.25. Due to the relation β = ακA20, the value of the alignment degree A20 for L3 sub-shell is determined to be 0.577 ± 0.08. Alignment degree A20 for L3 sub-shell is dependent on its intrinsic physical properties, while the anisotropy parameter β of typical X-rays can be affected by Coster-Kronig transition process. The behavior of the alignment for inner-shell vacancy states calls for more research results both in theory and in experiment. Therefore, it is quite relevant and meaningful to perform more experiments to further study the angular distribution of vacancy states by electrons, photons and ions impacting a target. -
Keywords:
- photoionization /
- characteristic X-rays /
- angular distribution /
- anisotropy parameter
[1] 杨蒙生, 易泰民, 郑凤成, 唐永建, 张林, 杜凯, 李宁, 赵利平, 柯博, 邢丕峰 2018 67 027301
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Google Scholar
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Google Scholar
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图 2 探测角度为140°时、中心能量为13.1 keV轫致辐射入射Au靶产生L系特征X射线能谱图
Fig. 2. Fitted L X-ray spectrum of Au induced by impact with bremsstrahlung with central energy of 13.1 keV and measured at the emission angle of 140°.
图 3 Au 靶特征X射线强度比I(Lα)/I(Lγ1)和I(Lι)/I(Lγ1)与P2(cosθ)的关系
Fig. 3. Intensity ratios of I(Lα)/I(Lγ1) and I(Lι)/I(Lγ1) as a function of P2(cosθ) for Au.
f12 f13 f23 0.083 0.644 0.132 
下载: 导出CSV
表 2 不同入射能量下L支壳层电离截面[26]及CK跃迁矫正因子κ值
Table 2. Ionization cross-sections (in barn) for L subshells[26] and CK correction factor κ at different energies.
E/keV σL1 σL2 σL3 κ 1.9 0 0 0 0 12 0 0 3.5629 × 104 1 13.76 0 0 2.4493 × 104 1 13.8 0 1.5567 × 104 2.3987 × 104 0.92 14.3 0 1.4574 × 104 2.2035 × 104 0.91 14.4 7.8361 × 103 1.4237 × 103 2.1575 × 104 0.80 15 7.4098 × 103 1.2777 × 104 1.9496 × 104 0.75 20 4.4219 × 103 6.1227 × 103 8.5173 × 103 0.7 30 1.993 × 103 1.9923 × 103 2.5531 × 103 0.62
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[1] 杨蒙生, 易泰民, 郑凤成, 唐永建, 张林, 杜凯, 李宁, 赵利平, 柯博, 邢丕峰 2018 67 027301
Google Scholar
Yang M S, Yi T M, Zheng F C, Tang Y J, Zhang L, Du K, Li N, Zhao L P, Ke B, Xing P F 2018 Acta Phys. Sin. 67 027301
Google Scholar
[2] 曾雄辉, 赵广军, 徐军 2004 53 1935
Google Scholar
Zeng X H, Zhao G J, Xu J 2004 Acta Phys. Sin. 53 1935
Google Scholar
[3] Nishimura F, Kim J, Yonezawa S, Takashima M 2014 J. Flu. Chem. 160 52
Google Scholar
[4] 戚俊成, 刘宾, 陈荣昌, 夏正德, 肖体乔 2019 68 024202
Google Scholar
Qi J C, Liu B, Chen R C, Xia Z D, Xiao T Q 2019 Acta Phys. Sin. 68 024202
Google Scholar
[5] 王琛, 安红海, 方智恒, 熊俊, 王伟, 孙今人 2018 67 015203
Google Scholar
Wang C, An H H, Fang Z H, Xiong J, Wang W, Sun J R 2018 Acta Phys. Sin. 67 015203
Google Scholar
[6] 张天奎, 于明海, 董克攻, 吴玉迟, 杨靖, 陈佳, 卢峰, 李纲, 朱斌, 谭放, 王少义, 闫永宏, 谷渝秋 2017 66 245201
Google Scholar
Zhang T K, Yu M H, Dong K G, Wu Y C, Yang J, Chen J, Lu F, Li G, Zhu B, Tan F, Wang S Y, Yan Y H, Gu Y Q 2017 Acta Phys. Sin. 66 245201
Google Scholar
[7] Flügge S, Mehlhorn M, Schmidt V 1972 Phys. Rev. Lett. 29 7
Google Scholar
[8] Berezhko E G, Kabachnik N M, Rostovsky V S 1978 J. Phys. B: At. Mol. Phys. 11 1749
Google Scholar
[9] Raza H S, Kim H J, Ha J M, Cho S O 2013 Appl. Radiat. Isot. 80 67
Google Scholar
[10] Bansal H, Kaur G, Tiwari M K, Mittal R 2016 Eur. Phys. J. D 70 84
Google Scholar
[11] Salem S, Stöhlker T, Brauning-Demian A, Hagmann S, Kozhuharov C, Liesen D 2013 Phys. Rev. A 88 012701
Google Scholar
[12] Özdemir Y, Durak R, Kacal M R, Kurudirek M 2011 Appl. Radiat. Isot. 69 991
Google Scholar
[13] Han I, Demir L 2011 J. X-Ray Sci. Technol. 19 13
Google Scholar
[14] Demir L, Şahin M, Söğűt Ö, Şahin Y 2000 Radiat. Phys. Chem. 59 355
Google Scholar
[15] Cooper J, Zare N 1969 Atomic Collision Processes (New York: Gordon & Breach) pp317−337
[16] Kumar A, Agnihotri A N, Chatterjee S, Kasthurirangan S, Misra D, Choudhury R K, Sarkadi L, Tribedi L C 2010 Phys. Rev. A 81 062709
Google Scholar
[17] Alrakabi M, Kumar S, Sharma V, Singh G, Mehta D 2013 Eur. Phys. J. D 67 99
Google Scholar
[18] Tartari A, Baraldi C, Casnati E, Da Re A, Jorge E F, Taioli S 2003 J. Phys. B 36 843
Google Scholar
[19] Kumar A, Puri S, MehtaD, Garg M L, Singh N 1999 J. Phys. B: At. Mol. Opt. Phys. 32 3701
Google Scholar
[20] Kumar A, Puri S, Shahi J S, Garg M L, Mehta D, Singh N 2001 J. Phys. B: At. Mol. Opt. Phys. 34 613
Google Scholar
[21] Gonzales D, Requena S, Williams S 2012 Appl. Radiat. Isot. 70 301
Google Scholar
[22] Berezhko E G, Kabachnik N M 1977 J. Phys. B: At. Mol. Opt. Phys. 10 2467
Google Scholar
[23] Yalçın P, Porikli S, Kurucu Y, Şahin Y 2008 Phys. Lett. B 663 186
Google Scholar
[24] Storm L, Israel H I 1970 At. Data Nucl. Data Tables 7 565
Google Scholar
[25] Bambynek W, Crasemann B, Fink R W, Freund H U, Mark H, Swift C D, Price R E, Rao P V 1972 Rev. Mod. Phys. 44 716
Google Scholar
[26] Scofield J H 1973 Theoretical Photoionization Cross-sections from 1 to 1500 keV (Livermore, CA: Lawrence Livermore Laboratory) Report No. UCRL-51326
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