[1] UNIV CALIF SANTA BARBARA, INST THEORET PHYS, SANTA BARBARA, CA 93106 USA
[2] COLL FRANCE, PHYS MAT CONDENSEE LAB, F-75231 PARIS 05, FRANCE
[3] UNIV CALIF LOS ANGELES, DEPT CHEM & BIOCHEM, LOS ANGELES, CA 90024 USA
[4] EXXON RES & ENGN CO, CORP RES SCI LABS, ANNANDALE, NJ 08801 USA