Studies on pure and doped C₆₀

Laszlo Mihaly

SUNY@Stony Brook

This talk has been presented at the Department of Physics, Brown University, 2/23/98. A part of it is based on publications listed here. Acknowledgements are here. MPEG, VRML, JAVA and other plugins are necessary to view the full content of these pages.

Outline

Method: IR spectroscopy

Mix of tabletop and large scale experiments

Measuring optical transmission, reflection as the function of frequency.
Two fundamental aspects:

molecular vibrations of simple and complicated molecules and
Example: linear molecule (Like CO₂ or CS₂)
free electron excitations

Materials: Fullerenes and fullerides

Fullerenes discovered in 1985 by Curl, Kroto and Smalley
Late breaking news
The most abundant fullerene, the C₆₀ molecule has icosahedral molecular symmetry,
Solid C₆₀ forms an approximate face centered cubic fcc structure
Solid C₆₀ can be doped with alkali metals and other elements and molecules.

Case study: modes in pure C₆₀

Four IR allowed modes
Spectrum of pure C₆₀ single crystal looks a bit more complex....

temperature dependence
pressure dependence
comparing the natural and C¹³ enriched single crystals

Model system: Liquid CS₂
Two sources of "extra" modes:

Many more modes than the four "allowed" IR active modes: symmetery breaking
Modes extend to high frequencies: anharmonicity
Not sensitive to C¹³, except for slight line broadening
Pressure dependence and temperature dependence suggests intramolecular coupling.
All 46 fundamental vibrational modes can be deduced.

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