H^(1+)和He^(2+)激发Au靶的M-X射线辐射

M-shell X-ray production induced by H^(1+) and He^(2+) on Au

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 Mζ and Mα 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.