15min:

WILLIAM G. HARTER AND HORACE T. CROGMAN, Department of Physics University of Arkansas Fayetteville, AR 72701.

Buckminsterfullerene (C₆₀) is the roundest commercially available deformable spherical rotors (DSR),. The "Buckyballs" are unique in that they have tri-axial rotation even in the fullerite solid-state above 140K; a box of frictionless ball bearings! Also, the C₆₀ cage is large enough to hold atoms and maybe even small molecules. In gas-phase this opens the possibility of a fully triaxial concentric DSR-DST rotor-rotor as well as many of the other more theoretically tractable cases like DSR-RDR or RST-RUP listed in the preceding talk. (C₆₀ solid-phase is a hetrocentric (DSR)^N fcc crystal.) Finally, C₆₀ is practically unique in that it comes in distinct isotopic varieties, most notably a "Bose-ball" ¹²C₆₀, a "mixed-ball" ¹³C₅₉ and a "Fermi-ball" of (¹³C₆₀)., Differences in symmetry between these casesis enormous. Bose-exclusion kills all but the Ag rovibrational species of ¹²C₆₀ and reduces spectral congestion by a factor of 60. In contrast, Pauli-Fermi-exclusion assigns 2⁶⁰~1.5E18 hyperfine levels to each rovibrational level of ¹³C₆₀. Mixed symmetry fullerenes ¹³C_m-¹²C_60-m[3] lie between the two extremes. The first "mixed-ball" ¹³C₆₀ - ¹²C₅₉ corresponds to a strong-coupling limit of an hcDSR-RDR model. This observation helps to clarify the enormous symmetry-exclusion diversity. At the bottom of the rotor-rotor symmetry hierarchy are the hetrocentric hcRDR-RDR or hcRAT-RAT arrangements of elongated molecules connected more or less loosely end-to-end, that is, links of folding polymer chains. Such chains and links are nano-sized quantum mechanical analogs of ancient slings, whips, and trebuchets with a devilish dynamics to match! And, biological systems cannot live without them.