H~(1+)和He~(2+)激发Au靶的M-X射线辐射
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摘要
利用兰州重离子加速器国家实验室提供的H~(1+)和He~(2+)的离子束入射Au靶表面,测量了激发靶原子的M壳层特征X射线辐射.实验结果显示:靶原子的特征X射线M_α和M_ζ产额以及X射线产生截面随入射离子的动能增加而增加,实验获得X射线产生截面数值与利用BEA近似、PWBA模型以及ECPSSR理论估算的结果相比较大,实验截面随动能增加的趋势同PWBA模型估算的趋势较为接近.通过进一步分析,我们认为:当入射离子接近高Z靶原子时,由于高Z靶原子的M壳层电子束缚能相对较小,使靶原子产生双重离化和多重离化,荧光产额显著增强,使X射线产生截面增大.
The X-ray emissions from H~(1+) and He~(2+) beams impinging on Au surface are measured. The results show that the yields and production cross sections of M_ζ and M_α of target atom Au increased with the kinetic energy of H~(1+) and He~(2+). The measured production cross sections are higher than the theoretical predictions based on the PWBA approximation, the BEA approximation and ECPSSR theory. The measured production cross sections increased trend with ionic kinetic energy close to the theoretical predictions based on the PWBA. The fluorescence yield is enhanced dramatically owing to multiple vacancies as the projectiles approach target atoms. In the low projectile-energy region(E <1 MeV), because the projectiles velocities are nearly the M-shell electronic Bohr velocity of the high-Z target atom, and the bound of target atomic nucleus to electron decrease, so multiple ionization effects easily occur. One would have to conclude that these theories clearly fail at low velocities due to the electrons be assumed to be at rest in the early stage of these theories were constituted.
The X-ray emissions from H~(1+) and He~(2+) beams impinging on Au surface are measured. The results show that the yields and production cross sections of M_ζ and M_α of target atom Au increased with the kinetic energy of H~(1+) and He~(2+). The measured production cross sections are higher than the theoretical predictions based on the PWBA approximation, the BEA approximation and ECPSSR theory. The measured production cross sections increased trend with ionic kinetic energy close to the theoretical predictions based on the PWBA. The fluorescence yield is enhanced dramatically owing to multiple vacancies as the projectiles approach target atoms. In the low projectile-energy region(E <1 MeV), because the projectiles velocities are nearly the M-shell electronic Bohr velocity of the high-Z target atom, and the bound of target atomic nucleus to electron decrease, so multiple ionization effects easily occur. One would have to conclude that these theories clearly fail at low velocities due to the electrons be assumed to be at rest in the early stage of these theories were constituted.
引文
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5 Cohen D D,Stelcer E,Crawford J,et al.Comparison of proton and helium induced M subshell X-ray production cross sections with the ECUSAR theory.Nucl Instrum Meth B,2014,318:11-14
6 Zhou X M,Zhao Y T,Cheng R,et al.K and L-shell X-ray production cross sections for 50-250 ke V proton impact on elements with Z=26-30.Nucl Instrum Meth B,2013,299:61-67
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16 Liu Z Q,Cipolla S J.ISICS:A program for calculating K-,L-and M-shell cross sections from ECPSSR theory using a personal computer.Comput Phys Commun,1996,97:315-330
17 Rodriguez-Fernandez L,Miranda J,Ruvalcaba-Sil J L,et al.Measurement of M-shell X-ray production induced by protons of 0.3-0.7 Me Von W,Au,Pb,Bi,Th and U.Nucl Instrum Meth B,2002,189:27-32
18 Lapicki G.The status of theoretical L-subshell ionization cross sections for protons.Nucl Instrum Meth B,2002,189:8-20
19 Czarnota M,Bana?D,Braziewicz J,et al.X-ray study of M-shell ionization of heavy atoms by 8.0-35.2 Me V Oq+ions:The role of the multiple-ionization effects.Phys Rev A,2009,79:032710
20 Singh Y,Tribedi L C.M-subshell X-ray production cross sections of Au induced by highly charged F,C,and Li ions and protons:A large enhancement in the M3 fluorescence yield.Phys Rev A,2002,66:062709
2 Mc Guire J H,Richard P.Procedure for computing cross sections for single and multiple ionization of atoms in the binary-encounter approximation by the impact of heavy charged particles.Phys Rev A,1973,8:1374-1384
3 Johnson D E,Basbas G,Mc Daniel F D.Nonrelativistic plane-wave Born-approximation calculations of direct Coulomb M-subshell ionization by charged particle.Atom Data Nucl Data,1979,24:1-11
4 Brandt W,Lapicki G.Energy-loss effect in inner-shell coulomb ionization by heavy charged particles.Phys Rev A,1981,23:1717-1729
5 Cohen D D,Stelcer E,Crawford J,et al.Comparison of proton and helium induced M subshell X-ray production cross sections with the ECUSAR theory.Nucl Instrum Meth B,2014,318:11-14
6 Zhou X M,Zhao Y T,Cheng R,et al.K and L-shell X-ray production cross sections for 50-250 ke V proton impact on elements with Z=26-30.Nucl Instrum Meth B,2013,299:61-67
7 Humcane O A,Callahan D A,Casey D T,et al.Fuel gain exceeding unity in an inertially confined fusion implosion.Nature,2014,506:343-350
8 Agarwal B K.X-Ray Spectroscopy(2nd ed).Berlin:Springer-Verlag,1991.89-104
9 Zhang X A,Zhao Y T,Hoffmann D,et al.X-ray emission of Xe 30+ion beam impacting on Au target.Laser Particle Beams,2011,29:265-268
10 Lapicki G,Mehta R,Duggan J L,et al.Multiple outer-shell ionization effect in inner-shell X-ray production by light ions.Phys Rev A,1986,34:3813-3821
11 Banars D,Pajek M,Semaniak J,et al.Multiple ionization effects in low-resolution X-ray spectra induced by energetic heavy ions.Nucl Instrum Meth B,2002,196:223-246
12 Garcia J D,Fortner R J,Kavanagh T M.Inner-shell vacancy production in ion-atom collisions.Rev Mod Phys,1973,45:111-177
13 Wang X,Zhao Y T,Cheng R,et al.Multiple ionization effects in M X-ray emission induced by heavy ions.Phys Lett A,2012,376:1197-1200
14 Braich J S,Verma P,Verma H R.M-shell X-ray production cross section measurements in Pb and Bi due to the impact of protons and nickel ions.J Phys B-At Mol Opt,1997,30:2359-2373
15 Mc Guire J E.Atomic n-shell Coster-Kronig,Auger,and radiative rates,and fluorescence yields for Ca-Th.Phys Rev A,1972,5:1043-1047
16 Liu Z Q,Cipolla S J.ISICS:A program for calculating K-,L-and M-shell cross sections from ECPSSR theory using a personal computer.Comput Phys Commun,1996,97:315-330
17 Rodriguez-Fernandez L,Miranda J,Ruvalcaba-Sil J L,et al.Measurement of M-shell X-ray production induced by protons of 0.3-0.7 Me Von W,Au,Pb,Bi,Th and U.Nucl Instrum Meth B,2002,189:27-32
18 Lapicki G.The status of theoretical L-subshell ionization cross sections for protons.Nucl Instrum Meth B,2002,189:8-20
19 Czarnota M,Bana?D,Braziewicz J,et al.X-ray study of M-shell ionization of heavy atoms by 8.0-35.2 Me V Oq+ions:The role of the multiple-ionization effects.Phys Rev A,2009,79:032710
20 Singh Y,Tribedi L C.M-subshell X-ray production cross sections of Au induced by highly charged F,C,and Li ions and protons:A large enhancement in the M3 fluorescence yield.Phys Rev A,2002,66:062709