THE 1ST DIPOLE-ALLOWED ELECTRONIC-TRANSITION 1 (1)SIGMA(U)(-X (1)SIGMA(G)(+) OF CO2())

The potential energy function of the 1 1SIGMA(u)+ excited state Of CO2 , which lies around 11 eV above the electronic ground state, has been investigated by ab initio multiconfiguration self-consistent field cal culations. It has been found that this state exhibits two minima on on e-dimensional cuts of the potential energy function along the bending coordinate. One minimum at colinear geometry has a Rydberg character, whereas the other one located at a bending angle of about 140-degrees has avalence character. Both minima are separated by a small barrier. This seems to be responsible for complicated splittings observed in th e absorption spectrum of the first dipole-allowed electronic transitio n Of CO2.