Electromagnetic transitions between states satisfying free-boundary conditions (10 pages)
Electromagnetic transitions between states satisfying free-boundary conditions (10 pages)
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满足自由边界条件的状态之间的电磁跃迁（10页）
DOI：
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发表时间：
2006
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通讯作者：
L. Nikolopoulos
中科院分区：
文献类型：
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作者：
L. Nikolopoulos
我们解决了计算球对称势中粒子状态之间的电磁跃迁矩阵元素的问题，在有限距离处没有假定边界条件（自由边界条件方法）。为此，薛定谔方程在半径为 R 的有限盒子中求解，并通过变分有限基集（B 样条）方法对适当归一化的束缚态和连续态进行数值表示。讨论了该方法中三种转移算子形式（长度、速度、加速度）之间的等价性，并在所有三种规范中计算了有界连续体和连续体-连续体矩阵元素。通过计算双光子电离截面和光电子角分布，给出了氢强电磁辐射的结果。事实证明，当允许连续体电离（阈值以上电离）时，本方法非常适合计算多光子跃迁。通过自由边界条件方法，对散射态密度的完全控制是可行的，因此，部分波之间的连续体的简并性得以保留。
We address the problem of calculating electromagnetic transition matrix elements between states of a particle in spherically symmetrical potentials with no assumed boundary conditions at finite distance (free-boundary-condition method). For this, the Schroedinger equation is solved in a finite box of radius R and bound and continuum states, appropriately normalized, are numerically represented, through a variational finite-basis-set (B-spline) approach. The equivalence between the three transition operator forms (length, velocity, acceleration), within this approach, is discussed, and bound-continuum and continuum-continuum matrix elements are calculated in all three gauges. Results for the strong electromagnetic radiation of hydrogen are presented through the calculation of two-photon ionization cross sections and photoelectron angular distributions. It is demonstrated that the present approach is well suited for the calculation of multiphoton transitions when ionization in the continuum is allowed (above-threshold ionization). With the free-boundary-condition method complete control over the density of scattering states is feasible and, as the result of that, the degeneracy in the continuum between partial waves is preserved.