Vibrational spectrum of the endohedral Y2C2@C-92 fullerene by Raman spectroscopy: Evidence for tunneling of the diatomic C-2 molecule

The structure and vibrational spectrum of the novel endohedral fullerene ${\mathrm{Y}}_{2}$C${}_{2}$@C${}_{92}$ was studied by Raman spectroscopy, with particular emphasis on the rotational transitions of the diatomic ${\mathrm{C}}_{2}$ unit in the low-energy Raman spectrum. We report evidence for tunneling of this unit through the ${\mathrm{C}}_{2}$ rotation plane and observe anomalous narrowing in a hindered rotational mode. We also report complementary density functional theory calculations that support our conclusions and discuss potential applications to quantum computing and nonvolatile memory devices.