Rotor in a cage: Infrared spectroscopy of an endohedral hydrogen-fullerene complex

Abstract

Coupled translation-rotation eigenstates of in and on the spectroscopically optimized interaction potential: Effects of cage anisotropy on the energy level structure and assignments

Interaction potential and infrared absorption of endohedral H2 in C60

“…9,18 The translation-rotation coupling is measured as a splitting of absorption lines in the IR spectrum. 6 Second, vibrational and translational motion amplitudes of H 2 are relatively large because of its small mass. This makes the potential for H 2 translational motion anharmonic and dependent on the vibrational state.…”

“…This method [1][2][3] results in sample quantities of the order of 100 mg and has made possible nuclear magnetic resonance (NMR), 4,5 infrared (IR), 6 and inelastic neutron scattering (INS) (Refs. 7 and 8) spectroscopic investigations of the trapped H 2 dynamics and stimulated theoretical investigations.…”

The dipolar endofullerene HF@C60

“…[2][3][4] Recently the approach has been extended to C 70 and C 59 N. [5][6][7] The confined molecules display quantization of their coupled translational and rotational degrees of freedom, and exhibit phenomena such as nuclear spin isomerism and orthopara conversion. [8][9][10][11][12] Recently it was shown that nuclear spin conversion of the encapsulated water molecules in H 2 O@C 60 leads to a change in the dielectric constant of the material. 13 One system of great interest is HF@C 60 , in which each fullerene cage contains a single hydrogen fluoride (HF) molecule.…”

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

“…We highlight the T-R levels i = 3-5 in table 2, which have n = j = 1, and owing to the T-R coupling [2,3] are split into three λ sublevels. This type of splitting has received considerable experimental scrutiny, in both INS [15,16] and IR spectroscopy [6]. Interestingly, in the case of HD@C 60 , the ordering of the λ sublevels in ascending energy is λ = 2, 0, 1, whereas, for H 2 @C 60 , the energy ordering is λ = 1, 2, 0 [2,3,5].…”

“…This T-R coupling manifests conspicuously through the entire T-R energy level structure, partially lifting the degeneracies, and splitting the eigenstates, of H 2 and HD in C 60 with simultaneous translational and rotational excitation [2,3,5]. Shortly thereafter, the first infrared (IR) spectra measured for H 2 @C 60 [6] showed absorption lines split into distinct peaks owing to the T-R coupling, as predicted by our calculations [2,3]. Subsequent IR spectroscopic studies of H 2 @C 60 [4] as well as of endohedral HD and D 2 in C 60 [7] have provided a great deal of valuable information about the T-R energy levels of the guest molecules and their interaction potentials with C 60 .…”