Infrared spectroscopy of small-molecule endofullerenes

Hydrogen is one of the few molecules that has been incarcerated in the molecular cage of C₆₀ to form the endohedral supramolecular complex H₂@C₆₀ In this confinement, hydrogen acquires new properties. Its translation motion, within the C₆₀ cavity, becomes quantized, is correlated with its rotation a...

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Published in:Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences physical, and engineering sciences, 2013-09, Vol.371 (1998), p.1-25
Main Authors: Rõõm, T., Peedu, L., Ge, Min, Hüvonen, D., Nagel, U., Ye, Shufeng, Xu, Minzhong, Bačić, Z., Mamone, S., Levitt, M. H., Carravetta, M., Chen, J. Y.-C., Lei, Xuegong, Turro, N. J., Murata, Y., Komatsu, K.
Format: Article
Language:English
Subjects:
Absorption spectra
Fullerenes
Ground state
Hydrogen
Infrared radiation
Infrared spectroscopy
Line spectra
Molecules
Quantum numbers
Rotational states
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Summary:Hydrogen is one of the few molecules that has been incarcerated in the molecular cage of C₆₀ to form the endohedral supramolecular complex H₂@C₆₀ In this confinement, hydrogen acquires new properties. Its translation motion, within the C₆₀ cavity, becomes quantized, is correlated with its rotation and breaks inversion symmetry that induces infrared (IR) activity of H₂. We apply IR spectroscopy to study the dynamics of hydrogen isotopologues H₂, D₂ and HD incarcerated in C₆₀. The translation and rotation modes appear as side bands to the hydrogen vibration mode in the mid-IR part of the absorption spectrum. Because of the large mass difference of hydrogen and C₆₀ and the high symmetry of C₆₀ the problem is almost identical to a vibrating rotor moving in a threedimensional spherical potential. We derive potential, rotation, vibration and dipole moment parameters from the analysis of the IR absorption spectra. Our results were used to derive the parameters of a pairwise additive five-dimensional potential energy surface for H₂@C₆₀. The same parameters were used to predict H₂ energies inside C₇₀. We compare the predicted energies and the low-temperature IR absorption spectra of H₂@C₆₀.
ISSN:1364-503X