A simple model for sequential multiphoton ionization by ultraintense x rays is presented. The derived scaling of the ion yield with pulse energy quantitatively reproduces the experimental data, which shows that the ion yield increases according to the “power-law” behavior typical of multiphoton ionization, followed by saturation at high pulse energies. The calculated average time interval between ionizations for producing ions at a certain charge state is found to be proportional to the pulse duration and independent of all other x-ray pulse parameters. This agrees with previous studies where the kinetic energy of fragment ions with a given charge state produced by the intense x-ray ionization of molecules was found to be independent of the pulse energy, but to increase with a smaller pulse duration due to the smaller time interval between ionizations.

中文翻译：

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超强 X 射线连续多光子电离的简单模型

提出了一个简单的超强 X 射线连续多光子电离模型。用脉冲能量导出的离子产额比例定量地再现了实验数据，这表明离子产额根据多光子电离的典型“幂律”行为增加，然后在高脉冲能量下饱和。计算出的用于在特定电荷状态下产生离子的电离之间的平均时间间隔与脉冲持续时间成正比，并且与所有其他 X 射线脉冲参数无关。这与先前的研究一致，其中发现由分子的强 x 射线电离产生的具有给定电荷状态的碎片离子的动能与脉冲能量无关，