1. Corporate Research Laboratories, Exxon Research & Engineering Co., Route 22 East, Annandale, New Jersey 08801
2. Corporate Research Laboratories, Exxon Research & Engineering Co., Route 22 East, Annandale, New Jersey 08801, and School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, U.K.
3. Cray Research, Inc., 655 E. Lone Oak Dr., Eagan, Minnesota 55121
4. Department of Chemistry, University of Exeter, Stocker Rd., Exeter EX4 4QD, UK
5. Department of Chemistry, Catholic University of Leuven, Celestijnenlaan 200F, 3001 Heverlee, (Leuven) Belgium