THEORETICAL-STUDY OF PHOTOELECTRON AND ULTRAVIOLET-SPECTRA OF THE CN- ANION

Molecular orbital configuration interaction (MO-CI) ab initio calculations were carried out in order to reproduce the photoionisation spectrum and the UV spectrum of the CN- anion. The photoionisation spectrum is compared with the one obtained experimentally for NaCN, which is dominated by emission from CN-. The potential curves of the first excited states of CN- were calculated. A 3-SIGMA+ state was found at 6.24 eV above the ground state (at the equilibrium distance) and a 3-pi state was found at 3.80 eV above the ground state. The first electronic transition was found to be 3-SIGMA+ --> X approximately 1-SIGMA+ rather than 3-pi --> X approximately 1-SIGMA+ as supposed until now.