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首页> 外文期刊>Nuclear instruments and methods in physics research >Lower and upper bounds on M-shell X-ray production cross sections by heavy ions
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Lower and upper bounds on M-shell X-ray production cross sections by heavy ions

机译：重离子在M壳X射线产生截面上的上下界

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In inner-shell ionization by heavy ions, a significant shift of X-ray lines to the higher energy side and broadening of the peaks indicate that simultaneous multiple ionization of the M and higher shells can dramatically change the values of the atomic parameters. _(14)Si~(3,4+) and _(16)S~(3,4+) ions in the energy range of 5-10 MeV were used to bombard gold (200 μg/cm~2) and bismuth (80 μg/cm~2) targets. Eight main M X-ray lines have been detected with a Si(Li) detector. Without a possibility for a realistic way to modify the atomic parameters and an accurate extraction of M-subshell ionization cross sections, theoretical cross sections for M-shell ionization are converted to X-ray production cross sections with two extreme choices that presume (ⅰ) no multiple ionization and (ⅱ) the certainty that all shells outer to the M-shell are completely ionized in the full multiple ionization. These choices impose the lower and upper limits on theoretical predictions. The X-ray production data should be bracketed by the bounds calculated with any theory. We test this proposition by comparison of the measured cross sections for production of the main X-ray lines and their sum for the total M-shell X-ray production with the predictions of the First Born and ECUSAR [G. Lapicki, Nucl. Instrum. Meth. B 189 (2002) 8] theories in those two extreme limits. With the extreme assumption of no multiple ionization, the First Born approximation shows overall satisfactory agreement with the data while the ECUSAR theory drastically underpredicts our measurements. With the opposite extreme assumption of the full multiple ionization, the ECUSAR exhibits better agreement with the data than the First Born approximation. While neither agreement suggests sure preference for either of these theories, such extreme conversions - as they would have for of any ionization theories - set the lower and upper bounds on their predictions.
机译：在通过重离子进行的内壳电离中，X射线线向较高能量侧的显着移动以及峰的变宽表明，M和较高壳同时进行多次电离可以极大地改变原子参数的值。使用能量范围为5-10 MeV的_（14）Si〜（3,4+）和_（16）S〜（3,4+）离子轰击金（200μg/ cm〜2）和铋（80μg/ cm〜2）的目标。用Si（Li）检测器检测到八条主要的M X射线线。无法用现实的方式修改原子参数并准确提取M-亚壳电离截面，将M-壳电离的理论截面转换为X射线产生截面时，有两个极端选择，假定（ⅰ）没有多重电离，并且（ⅱ）确定M壳外部的所有壳都在完全多重电离中被完全电离。这些选择对理论预测施加了上限和下限。 X射线产生数据应以任何理论计算出的范围括起来。我们通过比较主要X射线生产线的测量横截面和它们对M壳X射线总产量的总和，与First Born和ECUSAR的预测进行比较，从而验证了这一命题。拉皮基（Nucl。）仪器方法B 189（2002）8]在这两个极端极限中的理论。在没有多重电离的极端假设下，First Born近似值显示出与数据总体令人满意的一致性，而ECUSAR理论极大地低估了我们的测量结果。在完全多重电离的相反极端假设下，ECUSAR与数据的一致性比第一伯恩近似更好。虽然没有一个协议表明肯定会偏爱这些理论中的任何一个，但这种极端转换（如任何电离理论所希望的那样）为它们的预测设定了上限和下限。

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