Dissociative electron attachment in C2H via electronic resonances

Investigation of microwave-activated CH4/H-2 plasma used in chemical vapour deposition of diamond revealed the presence of electronically excited C-2(-)* (B-2 Sigma(+)(u)). Using high-level electronic structure methods, we investigate electronic structure of C2H- and suggest possible routes for the formation of C-2(-) 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 analysed using natural transition orbitals. We identified several resonances in C2H-, including the state that may lead to C-2(-)* (B-2 Sigma(+)(u)). [GRAPHICS]