Relativistic R -matrix calculations for the electron-impact excitation of neutral molybdenum

Abstract

A recent PISCES-B Mod experiment [Nishijima, J. Phys. B 43, 225701 (2010)JPAPEH0953-407510.1088/0953-4075/43/22/225701] has revealed up to a factor of 5 discrepancy between measurement and the two existing theoretical models [Badnell, J. Phys. B 29, 3683 (1996)JPAPEH0953-407510.1088/0953-4075/29/16/014; Bartschat, J. Phys. B 35, 2899 (2002)JPAPEH0953-407510.1088/0953-4075/35/13/305], providing important diagnostics for Mo i. In the following paper we address this issue by employing a relativistic atomic structure and R-matrix scattering calculations to improve upon the available models for future applications and benchmark results against a recent Compact Toroidal Hybrid experiment [Hartwell, Fusion Sci. Technol. 72, 76 (2017)FSTUCY1536-105510.1080/15361055.2017.1291046]. We determine the atomic structure of Mo i using grasp0, which implements the multiconfigurational Dirac-Fock method. Fine structure energies and radiative transition rates are presented and compared to existing experimental and theoretical values. The electron-impact excitation of Mo i is investigated using the relativistic R-matrix method and the parallel versions of the Dirac atomic R-matrix codes. Electron-impact excitation cross sections are presented and compared to the few available theoretical cross sections. Throughout, our emphasis is on improving the results for the zP1,2,3o5→aS25,zP2,3,4o7→aS37 and yP2,3,4o7→aS37 electric dipole transitions of particular relevance for diagnostic work.