Low and intermediate energy electron collisions with the C$_2^-$ molecular anion

TL;DR

This study uses the molecular R-matrix with pseudo-states method to analyze electron collisions with C$_2^-$, revealing resonances and providing insights into detachment and excitation processes relevant to molecular physics.

Contribution

It applies the MRMPS method to C$_2^-$, identifying shape resonances and their effects on electron detachment and excitation, advancing understanding of molecular anion collision dynamics.

Findings

Resonances above ionisation threshold identified in specific symmetries.

Pi_g resonances influence the detachment cross section.

Impact parameter collisions dominate the cross sections.

Abstract

Calculations are presented which use the molecular R-matrix with pseudo-states (MRMPS) method to treat electron impact electron detachment and electronic excitation of the carbon dimer anion. Resonances are found above the ionisation threshold of C$_2^-$ with $^1\Sigma^+_g$, $^1\Pi_g$ and $^3\Pi_g$ symmetry. These are shape resonances trapped by the effect of an attractive polarisation potential competing with a repulsive Coulomb interaction. The $\Pi_g$ resonances are found to give structure in the detachment cross section similar to that observed experimentally. Both excitation and detachment cross sections are found to be dominated by large impact parameter collisions whose contribution is modelled using the Born approximation.