Enhancements of Electron-Atom Collisions due to Pauli Repulsion in Neutron-Star Magnetic Fields

Abstract

Neutron star surfaces and atmospheres are unique environments that sustain the largest-known magnetic fields in the universe. Our knowledge of neutron star material properties, including the composition and equation of state, remains highly unconstrained. Electron-atom collisions are integral to theoretical thermal conduction and spectral emission models that describe neutron star surfaces. The theory of scattering in magnetic fields was developed in the 1970s, but focused only on bare nuclei scattering. In this work, we present a quantum treatment of atom-electron collisions in magnetic fields; of significant importance is the inclusion of Pauli repulsion arising from two interacting electrons. We find strange behaviors not seen in collisions without a magnetic field. In high magnetic fields, Pauli repulsion can lead to orders of magnitude enhancements of collision cross sections. Additionally, the elastic collision cross sections that involve the ground state become comparable to those involving excited states, and states with large orbits have the largest contribution to the collisions. We anticipate significant changes to transport properties and spectral line broadening in neutron star surfaces and atmospheres, which will aid in spectral diagnostics of these extreme environments.