Effective Core Potentials for Calculations of Continuum Spectra of Molecules Using the Molecular R-Matrix Method

Implementation of effective core potentials (ECPs) into the molecular scattering suite UKRmol+ is presented together with a set of calculations for a range of targets relevant for plasma modeling. Continuum description in scattering and photoionization calculations for large targets or high-energy electrons often requires the use of numerical continuum functions and the associated molecular integrals. We derive expressions for ECP integrals over B-spline-type orbitals using their momentum-space representation and describe their implementation. Sample calculations are presented for electron collision with ethylene (C₂H₄), bromine (Br₂), silicon tetrabromide (SiBr₄), and tungsten hydride (WH), as well as photoionization of methyl iodide (CH₃I).