Breit–Pauli R-Matrix approach for the time-dependent investigation of ultrafast processes

Abstract We have refactored the Breit–Pauli R-Matrix integral package within the RMatrxI package to employ a B-Spline basis to allow for level-resolved time-dependent R-Matrix calculations involving a laser pulse. The B-Spline approach independently verifies the accuracy of the current integral package pstg1r.f, but requires greater flexibility at the R-Matrix boundary when describing the continuum wavefunctions. This adaptation can be integrated with either the subsequent serial or parallel Breit–Pauli suite of codes. Program summary Program Title: BSplineStg1 Program Files doi: http://dx.doi.org/10.17632/prk6fsn56y.1 Licensing provisions: GPLv2 Programming language: Fortran 2003 Nature of problem: Previously, the time-dependent R-Matrix with Time-dependent (RMT) codes could only be used with atomic data from atomic physics codes which did not include spin–orbit effects. When we desire to include spin–orbit effects in a level resolved Time-dependent R-Matrix calculation, we must use a different atomic structure and integral package, such as the RMatrixI package. However, while the RMatrixI package is able to include spin–orbit effects, it was not previously compatible for use with RMT. Solution method: To enable compatibility between RMatrixI and RMT, we write an alternative to the Stg1 code within the RMatrixI package (titled BSplineStg1) that uses B-Spline techniques to create and describe continuum orbitals. The necessary one- and two-electron integrals for the remainder of the RMatrixI package are calculated using Gauss–Legendre integration. The remainder of the Breit–Pauli R-Matrix codes require no further modification.