BREMS: Partial-wave calculation of spectra and angular distributions of electron-atom bremsstrahlung at electron energies less than 30 MeV (New Version Announcement)

A new version of the Fortran program BREMS, which calculates single- and double-differential cross sections (DDCS) of electron-atom bremsstrahlung by the relativistic partial-wave method, is presented. The detailed description of the program is given in the original paper [Comput. Phys. Commun. 232 (2018) 237–255]. The new numerical methods implemented in the latest version include cubic spline interpolation of the radial matrix elements with respect to the orbital quantum number of the emitted photon, and usage of scaling properties of the partial-wave DDCS as a function of two variables – the photon emission angle and the number of partial waves retained in the truncated partial-wave series. As a result of improvements of efficiency and accuracy of the code, the endpoint of the energy range where the partial-wave calculations of bremsstrahlung cross sections are feasible has been increased by an order of magnitude (from 3 MeV to 30 MeV). In addition, three “special” modes of operation, which do not involve partial-wave calculations, but can be used to provide some auxiliary quantities, have been implemented.

本文提出了一种新的 Fortran 程序版本，名为 BREMS，该程序通过相对论性部分波方法计算电子-原子光电子能级跃迁的单一和双微分截面（DDCS）。该程序的具体描述详见原始论文[Comput. Phys. Commun. 232 (2018) 237–255]。最新版本中实施的数值方法包括根据发射光子的轨道量子数对径向矩阵元素进行三次样条插值，以及利用部分波 DDCS 的缩放特性作为两个变量——光子发射角和截断部分波级数中保留的部分波数——的函数。由于代码效率与精度的提升，部分波方法计算光电子能级跃迁截面的能量范围末端提高了十倍（从 3 MeV 提升至 30 MeV）。此外，还实现了三种“特殊”操作模式，这些模式不涉及部分波计算，但可用于提供一些辅助量。