An excess electron bound to urea oligomers. II. Chains and ribbons

The possibility of electron binding to chain- and ribbon-like urea oligomer s was studied at the second-order Moller-Plesset perturbation theory level as well as at the coupled cluster level with single, double, and noniterati ve triple excitations. It was found that all the chains form stable dipole- bound anions whose electron binding energies grow rapidly with chain length , while ribbon-type oligomers bind an excess electron only when they contai n an odd number of urea monomer units. Moreover, the chain oligomers suppor t bound excited anionic states of Sigma and Pi symmetry. (C) 2001 American Institute of Physics.