Predissociation dynamics of negative ion resonances of H$_2$ near 12 eV and 14.5 eV using velocity slice imaging technique

TL;DR

This study investigates the predissociation dynamics of negative ion resonances in molecular hydrogen near 12 and 14.5 eV using velocity slice imaging, revealing new insights into resonance structures and symmetry breaking.

Contribution

The paper provides new experimental evidence on the nature of H$_2$ negative ion resonances at specific energies, challenging previous assignments and highlighting the role of bound resonances.

Findings

Structures at 12 eV are due to predissociation of $C^2{\Sigma}_g^+$ resonance.

Structures at 14.4 eV are due to predissociation of a bound $^2{\Sigma}_g^+$ resonance.

Bound $^2{\Sigma}_g^+$ resonance contributes to inversion symmetry breaking near 14 eV.

Abstract

Dissociative electron attachment (DEA) is an important tool for investigating negative ion resonances. We have studied the negative ion resonances of H2 at 10 eV and 14 eV using the improved velocity slice imaging technique. We obtained modulations in the kinetic energy spectrum of H$^-$ ions obtained at 12 eV and 14.5 eV electron energy, consistent with the earlier reported vibrational state contributions from the higher lying bound resonances. We show that structures obtained at 12 eV are due to predissociation of the $C^2{\Sigma}_g^+$ resonance consistent with the current understanding. However, based on our angular distribution measurements, we propose that the structures obtained at 14.4 eV are due to predissociation of bound resonance of $^2{\Sigma}_g^+$ symmetry as against ${\delta}_g$ that was proposed earlier. We also report that the bound $^2{\Sigma}_g^+$ resonance contributes to the observed inversion symmetry breaking near 14 eV.