Quantum Translator-Rotator: Inelastic Neutron Scattering of Dihydrogen Molecules Trapped inside Anisotropic Fullerene Cages

Horsewill, A.J.; Panesar, Kuldeep; Rols, S.; Johnson, Mark R.; Murata, Yasujiro; Komatsu, Kôichi; Mamone, Salvatore; Danquigny, A.; Cuda, Francesco; Maltsev, Sergey; Grossel, Martin C.; Carravetta, Marina; Levitt, Malcolm H.

doi:10.1103/physrevlett.102.013001

Cited by 63 publications

(71 citation statements)

References 10 publications

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“…The first such physical investigation of H 2 O@C 60 was undertaken in 2012 at low temperature using three forms of spectroscopy; far-infrared, inelastic neutron scattering (INS) and solid state nuclear magnetic resonance (NMR). 4 Analogous to earlier investigations on other small molecule endofullerenes such as H 2 @C 60 , [5][6][7][8][9][10][11][12][13][14][15][16] these first experiments revealed the quantum rotation of the water molecule and conclusively identified its nuclear spinisomers, ortho-H 2 O and para-H 2 O, in the various spectra. The existence of these two species is founded in the requirement for the total wavefunction of the water molecule to be antisymmetric upon exchange of two fermions, in this case the two 1 H nuclei.…”

Section: Introductionsupporting

confidence: 72%

Symmetry-breaking in the endofullerene H₂O@C₆₀ revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

Goh

Jiménez‐Ruiz

Johnson

et al. 2014

Phys. Chem. Chem. Phys.

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a Inelastic neutron scattering (INS) has been employed to investigate the quantum dynamics of water molecules permanently entrapped inside the cages of C 60 fullerene molecules. This study of the supramolecular complex, H 2 O@C 60 , provides the unique opportunity to study isolated water molecules in a highly symmetric environment. Free from strong interactions, the water molecule has a high degree of rotational freedom enabling its nuclear spin isomers, ortho-H 2 O and para-H 2 O to be separately identified and studied. The INS technique mediates transitions between the ortho and para spin isomers and using three INS spectrometers, the rotational levels of H 2 O have been investigated, correlating well with the known levels in gaseous water. The slow process of nuclear spin conversion between ortho-H 2 O and para-H 2 O is revealed in the time dependence of the INS peak intensities over periods of many hours. Of particular interest to this study is the observed splitting of the ground state of ortho-H 2 O, raising the three-fold degeneracy into two states with degeneracy 2 and 1 respectively. This is attributed to a symmetry-breaking interaction of the water environment.

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Section: Introductionsupporting

confidence: 72%

Symmetry-breaking in the endofullerene H₂O@C₆₀ revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

Goh

Jiménez‐Ruiz

Johnson

et al. 2014

Phys. Chem. Chem. Phys.

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“…Translational excitation has little effect on the magnitude of the splittings of the rotational multiplets, except for the highest-frequency z-mode whose fundamental excitation increases the splitting of the j ) 1 triplet by 70% relative to that in the translational ground state (0, 0, 0). The agreement with the INS data 24 for H 2 @ATOCF is semiquantitative. Our calculations and the experiment agree that both the j ) 1 rotational level of the H 2 and the translational fundamental are fully split into a triplet.…”

Section: Discussionsupporting

confidence: 65%

“…Our calculated y-mode fundamental at 230.9 cm -1 agrees nicely with their estimate. A band of overlapping peaks was observed in the INS spectra, 24 in the range 230 -320 cm -1 . No assignment was attempted because of the expected presence of other translational excitations and cage deformation modes in this region.…”

Section: T-r Energy Levels Of P-h 2 Molecule In Atocfmentioning

confidence: 94%

“…Hence, the endohedral PES of H 2 @ATOCF exhibits the strongest radial anisotropy, while that of H 2 @ C 60 is the weakest. Another reason for focusing on H 2 @ATOCF is that it was the subject of a recent inelastic neutron scattering (INS) investigation, 24 in which a number of transitions among the discrete translational and rotational eigenstates of the caged H 2 were observed, providing an opportunity for a direct comparison with theory. The quantum dynamics of H 2 inside ATOCF has been also studied by NMR.…”

Section: Introductionmentioning

confidence: 99%

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Quantum Dynamics of a Hydrogen Molecule Inside an Anisotropic Open-Cage Fullerene: Coupled Translation-Rotation Eigenstates and Comparison with Inelastic Neutron Scattering Spectroscopy

Bačić

et al. 2010

J. Phys. Chem. A

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We report rigorous quantum five-dimensional (5D) calculations of the translation-rotation (T-R) energy levels and wave functions of H 2 inside aza-thia-open-cage fullerene (ATOCF). Translational and rotational excitations of this endohedral complex have been measured in a recent inelastic neutron scattering (INS) study, enabling direct comparison between theory and experiment. ATOCF has no symmetry, and therefore the intermolecular potential energy surface (PES) governing the T-R dynamics of H 2 is strongly anisotropic. A pairwise additive PES is employed in the calculations. Inspection of the wave functions shows three regular quasi-1D translational modes aligned with the Cartesian x, y, and z axes, respectively. These and other translational excitations can be assigned with the Cartesian quantum numbers V x , V y , and V z . The radial anisotropy of the cage environment causes the splitting of the translational fundamental into three excitations whose frequencies differ substantially; the z mode directed toward the ATOCF orifice has the lowest frequency and is the most anharmonic. All three translational modes exhibit negative anharmonicity. The j ) 1 rotational level of H 2 is also split into a triplet, due to the angular anisotropy of the cage. The complete lifting of the degeneracies of the translational fundamental and the j ) 1 triplet of the encapsulated H 2 molecule that emerges from the calculations is also observed in the INS spectra of H 2 @ATOCF. The calculated magnitudes of both splittings, as well as the energies of the individual sublevels, rotational and translational, are in good agreement with the INS data.

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“…Horsewill [14] and in C 60 [15,16]. These studies have determined the energies of the majority of the lower lying T-R eigenstates of H 2 @C 60 [16].…”

Section: Introductionmentioning

confidence: 99%

HD in C ₆₀ : theoretical prediction of the inelastic neutron scattering spectrum and its temperature dependence

Lawler

et al. 2013

Phil. Trans. R. Soc. A.

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One contribution of 13 to a Theo Murphy Meeting Issue 'Nanolaboratories: physics and chemistry of small-molecule endofullerenes' . We report rigorous quantum calculations of the inelastic neutron scattering (INS) spectra of HD@C 60 , over a range of temperatures from 0 to 240 K and for two incident neutron wavelengths used in recent experimental investigations. The computations were performed using our newly developed methodology, which incorporates the coupled five-dimensional translation-rotation (T-R) eigenstates of the guest molecule as the initial and final states of the INS transitions, and yields highly detailed spectra. Depending on the incident neutron wavelength, the number of computed INS transitions varies from almost 500 to over 2000. The low-temperature INS spectra display the fingerprints of the coupling between the translational and rotational motions of the entrapped HD molecule, which is responsible for the characteristic splitting patterns of the T-R energy levels. INS transitions from the ground T

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Quantum Translator-Rotator: Inelastic Neutron Scattering of Dihydrogen Molecules Trapped inside Anisotropic Fullerene Cages

Cited by 63 publications

References 10 publications

Symmetry-breaking in the endofullerene H₂O@C₆₀ revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

Symmetry-breaking in the endofullerene H₂O@C₆₀ revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

Quantum Dynamics of a Hydrogen Molecule Inside an Anisotropic Open-Cage Fullerene: Coupled Translation-Rotation Eigenstates and Comparison with Inelastic Neutron Scattering Spectroscopy

HD in C ₆₀ : theoretical prediction of the inelastic neutron scattering spectrum and its temperature dependence

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Quantum Translator-Rotator: Inelastic Neutron Scattering of Dihydrogen Molecules Trapped inside Anisotropic Fullerene Cages

Cited by 63 publications

References 10 publications

Symmetry-breaking in the endofullerene H2O@C60 revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

Symmetry-breaking in the endofullerene H2O@C60 revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

Quantum Dynamics of a Hydrogen Molecule Inside an Anisotropic Open-Cage Fullerene: Coupled Translation-Rotation Eigenstates and Comparison with Inelastic Neutron Scattering Spectroscopy

HD in C 60 : theoretical prediction of the inelastic neutron scattering spectrum and its temperature dependence

Contact Info

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Resources

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Symmetry-breaking in the endofullerene H₂O@C₆₀ revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

Symmetry-breaking in the endofullerene H₂O@C₆₀ revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

HD in C ₆₀ : theoretical prediction of the inelastic neutron scattering spectrum and its temperature dependence