Dissociative Electron Attachment to HCN and HNC

Previous experimental and theoretical studies on HCN and HNC have indicated the presence of both $\ensuremath{\sigma}$ and $\ensuremath{\pi}$ low-lying shape resonances. The energy and autoionization width of these resonant states depend on the stretching and bending of the molecule and lead primarily to a $({\text{CN}}^{\ensuremath{-}}+\text{H})$ product. In this work, we present a comparative study of the dissociation mechanism of these isomers. We carried out electron scattering calculations using the complex-Kohn variational method as a function of the three internal degrees of freedom to obtain the resonance energy surfaces and autoionization widths. We then use these data as input to form the Hamiltonian relevant to the nuclear dynamics. The multidimensional wave equation is solved using the multiconfiguration time-dependent Hartree approach. We compute the relative dissociative electron attachment cross sections and examine the isotope effect relative to each isomer.