Rotor in a Cage: Infrared Spectroscopy of an Endohedral Hydrogen-Fullerene Complex

ORAL

Abstract

We report the observation of quantized translational and rotational motion of molecular hydrogen inside the cages of C$_{60}$. Narrow infrared absorption lines at the temperature of 6\,K correspond to vibrational excitations in combination with translational and rotational excitations and show well-resolved splittings due to the coupling between translational and rotational modes of the endohedral H$_2$ molecule. A theoretical model shows that H$_2$ inside C$_{60}$ is a three-dimensional quantum rotor moving in a nearly spherical potential. The theory provides both the frequencies and the intensities of the observed infrared transitions. Good agreement with the experimental results is obtained by fitting a small number of empirical parameters to describe the confining potential, as well as the {\it ortho\/} to {\it para\/} ratio at 6\,K and at elevated temperatures [S. Mamone, et al., arXiv:0807.1589v2].

*The support by the EstSF grants 6138 and 7011, the EPSRC, and the University Research Fellowship (Royal Society) is acknowledged.

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Authors

  • Toomas R{\~o}{\~o}m

    • NICPB, Akadeemia tee 23, 12618 Tallinn, Estonia

  • Min Ge

    • NICPB, Akadeemia tee 23, 12618 Tallinn, Estonia

  • D. H{\"u}vonen

    • NICPB, Akadeemia tee 23, 12618 Tallinn, Estonia

  • U. Nagel

    • NICPB, Akadeemia tee 23, 12618 Tallinn
    • NICPB, Akadeemia tee 23, 12618 Tallinn, Estonia

  • S. Mamone

    • School of Chemistry, Southampton University, Southampton SO17 1BJ, UK

  • A. Danquigny

    • School of Chemistry, Southampton University, Southampton SO17 1BJ, UK

  • F. Cuda

    • School of Chemistry, Southampton University, Southampton SO17 1BJ, UK

  • M. C. Grossel

    • School of Chemistry, Southampton University, Southampton SO17 1BJ, UK

  • M. Carravetta

    • School of Chemistry, Southampton University, Southampton SO17 1BJ, UK

  • M. H. Levitt

    • School of Chemistry, Southampton University, Southampton SO17 1BJ, UK

  • Y. Murata

    • Institute for Chemical Research, Kyoto University, Kyoto 611-0011, Japan

  • K. Komatsu

    • Institute for Chemical Research, Kyoto University, Kyoto 611-0011, Japan