Dissociative Electron Attachment in C2H via Electronic Resonances

Investigation of microwave-activated CH₄/H₂ plasma used in chemical vapor deposition of diamond revealed the presence of electronically excited C₂^-(B²Σ_u⁺). Using high-level electronic structure methods, we investigate electronic structure of C₂H^- and suggest possible routes for formation of C₂^- in the ground (X²Σ_g⁺) and excited (B²Σ_u⁺) states via electronic resonances. To describe electronically meta-stable states, we employ the equation-of-motion coupled-cluster method augmented by the complex absorbing potential. The resonance wave-functions are analyzed using natural transition orbitals. We identified several resonances in C₂H^-, including the state that may lead to C₂^-(B²Σ_u⁺).