1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2. P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, 231 S 34th St., Philadelphia, Pennsylvania 19104, USA
3. Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
4. Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, Florida 32306, USA
5. Materials and Physics Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA