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采用孤立实激发与速度影像技术相结合的方法，研究了Eu原子4f76p1/2ns（n=7，9）自电离过程的动力学特性，包括弹射电子的角分布和向各离子态衰变的分支比. 首先，采用孤立实激发技术将Eu原子分步从基态4f76s2经中间态4f76s6p激发至4f76sns Rydberg态，并通过第三步跃迁4f76s+4f76p1/2+将其激发至4f76p1/2ns自电离态. 其次，运用速度影像技术对上述自电离过程进行探测，并通过一系列数学变换计算出该过程的弹射电子的能量分布和角向分布. 本文不仅分析和比较了各个态自电离衰变的分支比和各向异性参数随光子能量的变化规律，还深入讨论了它们与自电离光谱之间的对应关系. 最后，依据自电离衰变的分支比，探讨了实现Eu 离子粒子数反转的可能性，为实现自电离激光器提供了有价值的信息.
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关键词:
- Eu原子 /
- 4f76p1/2ns自电离态 /
- 角分布 /
- 分支比
To explore the dynamic properties of Eu 4f76p1/2ns autoionization process, the autoionization branching ratios of ions and the angular distributions of ejected electrons from the Eu 4f76p1/2ns (n=7, 9) autoionizing states are systematically investigated with the combination of the three-step isolated-core excitation (ICE) and the velocity-map imaging techniques The Eu 4f76sns Rydberg states are populated via a two-step laser excitation, from which the Eu 4f76p1/2ns autoionizing states are excited by the wavelength of the third laser around the Eu 6s+6p1/2+ ionic resonance in order to obtain autoionization spectra and the velocity-map images of ejected electrons from the Eu 4f76p1/2ns autoionizing states. Once the velocity-map images have been measured, both the energy distribution and angular distribution of ejected electrons can be acquired. Moreover, the spectra of the branching ratios and the anisotropic parameters within the autoionization resonances are also measured to observe their energy dependence and the relation with the autoionization spectra. Comparisons of the observed spectra of 4f76p1/2ns autoionizing states with n = 7, 8, and 9 manifest that the ICE technique is more suitable for the higher-n members of autoionization series. It is found that the Eu atoms in the 4f76p1/2ns (n = 8, 9) autoionizing states mainly decay into 4f75d+(9D) ionic state, leading to the population inversion between 4f75d+(9D) and 4f76s+ (7S) or 4f76s+ (9S) ionic states, which is significant for developing the autoionization laser. The angular distributions of the ejected electrons from the Eu 4f76p1/2ns autoionizing states show simple patterns at the energy points corresponding to the peaks of autoionization spectra, and have complicated patterns in the energy regions off the peaks of autoionization spectra, especially in the regions corresponding to the sharp increase or decrease in the autoionization spectra. The above phenomena can be explained with the strength of configuration interaction among different autoionization series converging to different ionic states, which is fluctuated within the energy region of autoionization spectra. In addition, within the autoionization resonance both the spectra of branching ratios and anisotropic parameters vary irregularly, and no obvious correlation with the spectra of 4f76p1/2ns autoionizing states can be found.-
Keywords:
- Eu atom /
- 4f76p1/2ns autoionizing state /
- angular distribution /
- branching ratio
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[6] Zhang Y, Dai C J 2003 J. Electron Spectrosc. 128 135
[7] Nakhate S G, Razvi M A N, Connerade J P, Ahmad S A 1996 J. Phys. B: At. Mol. Opt. Phys. 29 1439
[8] Bhattacharyya S, D'souza R, Rao P M, Razvi M A N 2003 Spectrochim Acta Part B 58 469
[9] Bhattacharyya S, Razvi M A N, Cohen S, Nakhate S G 2007 Phys. Rev. A 76 012502
[10] Xiao Y, Dai C J, Qin W J 2010 Chin. Phys. B 19 063202
[11] Wang X, Shen L, Dai C J {2012 J. Phys. B: At. Mol. Opt. Phys. 45 5001
[12] Kachru R, Tran N H, Pillet P, Gallagher T F 1985 Phys. Rev. A 31 218
[13] Stodolna A S, Rouzee A, Lepine F, Cohen S, Robicheaux F, Gijsbertsen A, Jungmann J H, Bordas C, Vrakking M J J 2013 Phys. Rev. Lett. 110 3001
[14] Goto M, Hansen K 2012 Phys. Scr. 86 035303
[15] Liang H R, Shen L, Jing H, Dai C J 2014 Acta Phys. Sin. 63 133202 (in Chinese) [梁洪瑞, 沈礼, 荆华, 戴长建 2014 63 133202]
[16] Dong C, Shen L, Yang J H, Dai C J {2014 Acta Opt. Sin. 34 0702001 (in Chinese) [董程, 沈礼, 杨金红, 戴长建 2014 光学学报 34 0702001]
[17] Dai C J, Schinn G W, Gallagher T F 1990 Phys. Rev. A 42 223
[18] Martin W C, Zalubas Romuald, Hagan Lucy 1978 Atomic Energy Levels (Washington: U.S. Government Printing Office) pp185-198
[19] Miranda E R, Valdos L R B, Ramirez E G, Lumbreras D A, Anaya T S, Vargas J J R, Hernandez J J V, Argelles V T, Castano V M 2013 J. Eur. Opt. Soc.-Rapid 8 13036
[20] Bokor J, Freeman R R, Cooke W E 1982 Phys. Rev. Lett. 48 1242
[21] Freeman R R, Bokor J, Cooke W E 1982 Phys. Rev. A 26 3029
[22] Lindsay M D, Cai L T, Schinn G W, Dai C J, Gallagher T F 1992 Phys. Rev. A 45 231
[23] Tauro S, Liu K 2008 J Phys B: At. Mol. Opt. Phys. 41 225001
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[1] Jones R R, Dai C J, Gallagher T F 1990 Phys. Rev. A 41 316
[2] Lindsay M D, Dai C J, Lyons B J, Mahon C R, Gallagher T F 1994 Phys. Rev. A 50 5058
[3] Dai C J 1995 Phys. Rev. A 52 4416
[4] Lindsay M D, Dai C J 1992 Phys. Rev. A 46 3789
[5] L J, Dai C J, Xu Y F, Li S B 2001 Chin. Phys. Lett. 18 516
[6] Zhang Y, Dai C J 2003 J. Electron Spectrosc. 128 135
[7] Nakhate S G, Razvi M A N, Connerade J P, Ahmad S A 1996 J. Phys. B: At. Mol. Opt. Phys. 29 1439
[8] Bhattacharyya S, D'souza R, Rao P M, Razvi M A N 2003 Spectrochim Acta Part B 58 469
[9] Bhattacharyya S, Razvi M A N, Cohen S, Nakhate S G 2007 Phys. Rev. A 76 012502
[10] Xiao Y, Dai C J, Qin W J 2010 Chin. Phys. B 19 063202
[11] Wang X, Shen L, Dai C J {2012 J. Phys. B: At. Mol. Opt. Phys. 45 5001
[12] Kachru R, Tran N H, Pillet P, Gallagher T F 1985 Phys. Rev. A 31 218
[13] Stodolna A S, Rouzee A, Lepine F, Cohen S, Robicheaux F, Gijsbertsen A, Jungmann J H, Bordas C, Vrakking M J J 2013 Phys. Rev. Lett. 110 3001
[14] Goto M, Hansen K 2012 Phys. Scr. 86 035303
[15] Liang H R, Shen L, Jing H, Dai C J 2014 Acta Phys. Sin. 63 133202 (in Chinese) [梁洪瑞, 沈礼, 荆华, 戴长建 2014 63 133202]
[16] Dong C, Shen L, Yang J H, Dai C J {2014 Acta Opt. Sin. 34 0702001 (in Chinese) [董程, 沈礼, 杨金红, 戴长建 2014 光学学报 34 0702001]
[17] Dai C J, Schinn G W, Gallagher T F 1990 Phys. Rev. A 42 223
[18] Martin W C, Zalubas Romuald, Hagan Lucy 1978 Atomic Energy Levels (Washington: U.S. Government Printing Office) pp185-198
[19] Miranda E R, Valdos L R B, Ramirez E G, Lumbreras D A, Anaya T S, Vargas J J R, Hernandez J J V, Argelles V T, Castano V M 2013 J. Eur. Opt. Soc.-Rapid 8 13036
[20] Bokor J, Freeman R R, Cooke W E 1982 Phys. Rev. Lett. 48 1242
[21] Freeman R R, Bokor J, Cooke W E 1982 Phys. Rev. A 26 3029
[22] Lindsay M D, Cai L T, Schinn G W, Dai C J, Gallagher T F 1992 Phys. Rev. A 45 231
[23] Tauro S, Liu K 2008 J Phys B: At. Mol. Opt. Phys. 41 225001
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