Dissociative ionization cross-sections and the rate coefficients of H₂S, OCS, LiH, and SiC

¹ Department of Physics, School of Advanced Sciences, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India
² School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK

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Received: 10 December 2025
Accepted: 20 February 2026

Abstract

Context. Electron-molecule and positron-molecule interactions play a major role in the interstellar medium. Although several inelastic channels have been studied in the literature, dissociative ionization studies of molecules are scarce.

Aims. To calculate the dissociative ionization cross-sections of cations emerging from H₂S, OCS, LiH, and SiC, we present the theoretical dissociative ionization cross-sections for the first time.

Methods. We computed electron and positron impact ionization cross-sections using a semi-empirical binary encounter Bethe (BEB) method and we computed the partial ionization cross-sections (PICS) of cations using the mass spectrum dependence method coupled with BEB. We used the Relative and Absolute Partial Ionization and Dissociation cross-section code to calculate the dissociation energies.

Results. We present our findings on the dissociation energies of cations, along with the electron impact the PICS of cations, the total electron-impact and direct positron-impact ionization cross-sections of neutral molecules (TICS and DICS), and the ionization rate coefficients of cations.

Conclusions. The PICS calculations show a plausible agreement with the measured data for cations. In the case of dications, the present model fails to reproduce the experimental cross-sections. This study is the first to present Maxwellian rates for partial cross-sections.