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

TL;DR

This paper presents a quantum model of electron-atom collisions in neutron star magnetic fields, highlighting how Pauli repulsion dramatically increases collision cross sections and affects spectral properties.

Contribution

It introduces a novel quantum treatment of atom-electron collisions in magnetic fields, including Pauli repulsion, revealing behaviors not seen in previous models.

Findings

Pauli repulsion causes orders of magnitude increase in collision cross sections

Elastic collision cross sections become comparable for ground and excited states

Large orbit states contribute most to collision processes

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.