Dissociative recombination measurements of HCl+ using an ion storage ring

TL;DR

This study measures the dissociative recombination rate of HCl+ ions with electrons using an advanced ion storage ring technique, providing more accurate data that can improve astrochemical models of chlorine-bearing molecules.

Contribution

Introduces a new method for deriving the cross section from recombination measurements, improving accuracy over previous approaches.

Findings

Recombination rate coefficients were measured from 0 to 4.5 eV collision energy.

The new data correct previous estimates, showing underestimation at 10 K and overestimation at 300 K.

Results help reconcile discrepancies in astrochemical models of chlorine molecules.

Abstract

We have measured dissociative recombination of HCl+ with electrons using a merged beams configuration at the heavy-ion storage ring TSR located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. We present the measured absolute merged beams recombination rate coefficient for collision energies from 0 to 4.5 eV. We have also developed a new method for deriving the cross section from the measurements. Our approach does not suffer from approximations made by previously used methods. The cross section was transformed to a plasma rate coefficient for the electron temperature range from T=10 to 5000 K. We show that the previously used HCl+ DR data underestimate the plasma rate coefficient by a factor of 1.5 at T=10 K and overestimate it by a factor of 3.0 at T=300 K. We also find that the new data may partly explain existing discrepancies between observed abundances of chlorine-bearing molecules and their astrochemical models.