Shape resonance in electron- atom and electron-molecule molecule collision:
Complex absorbing potential based coupled-cluster theory

Electron-atom and electron-molecule shape resonance leads to metastable resonant states, which become unnormalizable. Thus, bound state quantum chemistry techniques can not be applied. However, using complex absorbing potential and complex scaling, resonant states can be normalized. Using bound state coupled-cluster methods to the complex Hamiltonian, resonance energies can be obtained as real part of complex electron affinity and resonance widths can be obtained as imaginary part. Test results to prototype systems are presented.