Dissociative electron attachment in C₂H via electronic resonances

Abstract

Investigation of microwave-activated CH${}_4$/H${}_2$ plasma used in chemical vapour deposition of diamond revealed the presence of electronically excited C${}_2^{-\ast }$ (B${}^2{\mathrm{\Sigma }}_u^{+}$). Using high-level electronic structure methods, we investigate electronic structure of C${}_2$H${}^{-}$ and suggest possible routes for the formation of C${}_2^{-}$ in the ground (X${}^2{\mathrm{\Sigma }}_g^{+}$) and excited (B${}^2{\mathrm{\Sigma }}_u^{+}$) states via electronic resonances. To describe electronically metastable states, we employ the equation-of-motion coupled-cluster method augmented by the complex absorbing potential. The resonance wavefunctions are analysed using natural transition orbitals. We identified several resonances in C${}_2$H${}^{-}$, including the state that may lead to C${}_2^{-\ast }$ (B${}^2{\mathrm{\Sigma }}_u^{+}$).

GRAPHICAL ABSTRACT

Keywords:

• Electronic resonance
• EOM-CCSD
• Plasma physics
• Non-Hermitian quantum mechanics
• Dissociative electron attachment

Disclosure statement

A.I.K. is the president and a part-owner of Q-Chem, Inc. No potential conflict of interest was reported by S. G.

Additional information

Funding

This work was supported by NSF [CHE-1856342].