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

Abstract

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

The HD molecule in small and medium cages of clathrate hydrates: Quantum dynamics studied by neutron scattering measurements and computation

“…6 and 7, which was recently applied also to HD in C 60 . 29 To compare with the experimental results, the theoretically computed intensity of each transition between discrete TR states has been broadened by a Gaussian lineshape having a width equal to the MARI instrumental resolution, namely, 1.27 and 2.28 meV, for E 0 = 25 and 45 meV, respectively. The S(Q, E) so derived has been grouped into a limited number of spectra, each one obtained by integration in a 0.5 Å −1 wide range of Q , with the average Q value ranging from 1.0 Å −1 to 8 Å −1 with 0.5 Å −1 steps.…”

A Solid‐State Intramolecular Wittig Reaction Enables Efficient Synthesis of Endofullerenes Including Ne@C60, 3He@C60, and HD@C60

“…HD@C 60 has been prepared before, and its IR and inelastic neutron scattering (INS) spectra acquired, but as a mixture with H 2 @C 60 and D 2 @C 60 [23a,b] . Detailed predictions of the variable temperature INS spectra of HD@C 60 have been made, [24] but to test them experimentally requires a large sample of pure material. Although the use of solid‐state filling helps overcome the problem of the high cost of the gas, the low pressure (10 atm) at which HD is available limits the pressure our intensifier could generate to 80–85 atm.…”

The Endofullerene HF@C60: Inelastic Neutron Scattering Spectra from Quantum Simulations and Experiment, Validity of the Selection Rule, and Symmetry Breaking

“…The INS selection rule in question, in its original form, , states that for a para -H 2 or HD molecule confined in a near-spherical nanocavity, such as that of C 60 , the INS transitions between its ground TR state and excited TR states assigned as ( n , l , j , λ) are forbidden for λ = j + l – 1. Using two very different approaches, , this expression was subsequently generalized to λ = j + l – o , where o is a positive odd integer.…”

“…Also for the first time in the INS calculations for light-molecule endofullerenes, the guest molecule, HF, is not H 2 or one of its isotopologues. This has allowed us to test the prediction that the INS selection rule initially derived for H 2 or HD in a near-spherical nanocavity, , and later generalized, , applies to a much broader class of diatomic molecules in such a confinement. HF presents a challenge, owing to its large mass asymmetry and because n , l , j are not nearly as good quantum numbers as they are for H 2 .…”