高密度体系光电离截面新表达式的应用

利用实验光谱学的Beer Lambert定律和介质中的麦克斯韦方程组，建立了精确的光吸收（光电离）截面表达式，并通过一个随体系粒子数密度和宏观复介电常数而变化的变换函数，将严格截面公式与Fano和Cooper 1968年建立的理想气体的光电离截面公式直接联系起来.建议：1)当知道某密度下正确的体系宏观复介电常数β,γ时，可直接由严格表达式求得高密度下非理想状态的正确光电离截面；2)或当知道该体系的粒子微观极化率η,ζ和其理想气体的精确截面时，用上述变换公式间接求得其他密度时的光电离截面.对氩原子和氙原子的应用表明：当缺乏β,γ时，可由某一合理的宏观电极化率物理（例如克劳修斯-莫索缔）模型来计算β,γ，从而获得高密度体系的截面.这样获得的结果符合被散射物质的光电离（光吸收）截面随体系粒子数密度增大而增加的客观散射现象.而且，考虑了高密度真实体系中粒子间相互作用的宏观电极化率模型越正确，如此求得的散射截面的误差就越小. 关键词： 光电离截面 光吸收截面 介电常数 极化率

A new expression for photoionization cross sections and its application in high density system

A new expression for photoionization cross section has been proposed based on the Beer_Lambert's law and Maxwell equations for a material.And we also proposed a function varying with the number density of the system,which includes the local field effect and the higher_order dielectric correction to the famous formula for photoionization cross section of isolated atoms,proposed by Fano and Cooper in 1968 The photoionization cross sections of solid xenon have been studied by using this alternative expression which couples the macroproperty and the quantum quantity of the photoionization system,and which makes it possible for one to study the influence of induced dipoles on the photoionization.The dielectric behaviors of the matter in condensed state under several physical conditions (given the complex dielectric constants or the model of electric susceptibility of the system) are considered using our new expression for photoionization cross sections.The results show that it is reasonable in physics to calculate the cross sections of atoms in a real system by using the accurate expression.Furthermore,the more correct the model of electric susceptibility for the real system,the more accurate the cross section obtained from our formula will be.