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-*. Using high-level electronic structure methods, we investigate electronic structure of C2H- and suggest possible routes for formation of C2- in the ground (X$^2\Sigma_g^+$) and excited (B$^2\Sigma_u^+$) 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 analyzed using natural transition orbitals. We identified several resonances in C2H-, including the state that may lead to C2-* (B$^2\Sigma_u^+$).