The infrared spectrum of the acetylene radical cation C2H+2. A theoretical study using SCF, MCSCF, and CI methods

Within the harmonic approximation, the vibrational frequencies and infrared intensities of the C2H+ 2 electronic ground state have been predicted using ab initio molecular quantum mechanics. A standard double zeta plus polarization (DZ+P) basis set of contracted Gaussian functions was employed. Self-consistent-field (SCF), multiconfiguration (MC) SCF, and configuration interaction (CI) methods were used.