Cross sections for photo-induced bound-free and free-free transitions in plasmas are evaluated in the average-atom approximation and applied to determine opacities of dense plasmas of light elements. Parameters characterizing the plasmas (chemical potential, average ionic charge, free electron density, bound and continuum wave functions, and occupation numbers) are obtained from the average-atom model. Lowest-order calculations of the free-free cross sections, which diverge in the low-frequency limit, are regularized by accounting for the finite electron-ion relaxation time. The resulting analysis provides the basis for average-atom studies of plasma opacities. Such studies are presented for dense lithium, beryllium, boron, and carbon. Applications are given to Rosseland mean opacities of dense hydrogen and deuterium plasmas and to comparisons of free-free to bound-free opacities in shock-compressed plasmas. Average-atom cross section and opacity calculations are extended to plasmas consisting of more than one ionic species, boron nitride, polystyrene, and a composite H, He, C plasma.

中文翻译：

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稠密等离子体中自由结合和自由结合截面的平均原子计算

在平均原子近似中评估光诱导等离子体中无键和无键跃迁的截面，并将其应用于确定轻元素的密集等离子体的不透明度。从平均原子模型获得表征等离子体的参数（化学势，平均离子电荷，自由电子密度，束缚和连续波函数以及占有数）。通过考虑有限的电子离子弛豫时间，对自由自由截面的最低阶计算（在低频范围内发散）进行了正则化。所得分析为血浆不透明度的平均原子研究提供了基础。提出了有关致密的锂，铍，硼和碳的研究。Rosseland适用于稠密氢和氘等离子体的平均混浊度，以及在冲击压缩等离子体中的自由混浊度与自由束缚混浊度的比较。平均原子的横截面和不透明度的计算扩展到包括一种以上离子物种，氮化硼，聚苯乙烯和复合H，He，C等离子体的等离子体。