General ILL seminar
organised by College 7
Monday, 1 December 2025 at 15h00
Seminar room 110-111, ILL 50, 1st floor
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“ Endofullerenes: What can inelastic neutron scattering tell us about molecules and atoms trapped inside nanoscale carbon cages? ”
Malcolm Levitt
University of Southampton, UK, mhl@soton.ac.uk
Molecular endofullerenes consist of symmetrical carbon cages, with each cage fully encapsulating a single atom or small molecule. Most of these remarkable systems are synthesized by “molecular surgery” in which multistep organic syntheses lead to the opening of an orifice in the closed fullerene cage, the insertion of a molecule or atom through the orifice, and the suturing of the cage. This leads to a system in which single atoms or molecules are fully confined but completely free to rotate and translate, even at cryogenic temperatures. The molecule behaves as a real-world “particle in a box” with quantized energy levels given by the solutions of the Schrödinger equation. To date molecular endofullerenes containing H2, H2O, HF, CH4, CO, NO, and CH2O are known, as well as atomic endofullerenes containing the noble gas atoms He, Ne and Ar. The quantum states of the encapsulated molecules and atoms have been studied by inelastic neutron scattering, cryogenic NMR, infrared spectroscopy, and terahertz spectroscopy. As well as the “particle in a box” features of the molecular quantum mechanics, which is beautifully revealed by INS, many of the systems display spin isomerism, which may be studied by NMR, terahertz spectroscopy, infrared spectroscopy, as well as INS. I will review the main features of the quantum mechanics and spectroscopy of these unique systems, and some of the physical methods which are used to study them.
Several new systems have recently been produced and are currently under study at the ILL. These include:
H2@C70, which has single H2 molecules encapsulated inside the elongated cage of C70.
2H2@C70, which has pairs of H2 molecules encapsulated inside the same C70 cage. We expect INS and NMR to reveal details of how the two H2 molecules interact with each other when confined in the same cavity.
Rb3(H2@C60), which is a superconductor below ~ 30K. Some theoretical models of the non-conventional superconductivity in this material postulate Jahn-Teller distortions of the C60 cage as an element of the mechanism. We anticipate that the JT distortion will be revealed as a splitting of the triply-degenerate J=1 rotational state of H2.
Mohamed Zbiri (College 7 Secretary)
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