Inelastic neutron scattering investigations of the quantum molecular dynamics of a H2molecule entrapped inside a fullerene cage

Abstract

The quantum dynamics of dihydrogen molecules entrapped inside fullerene cages has been investigated using inelastic neutron scattering (INS). For the endofullerene H 2 @C 60 the low-lying energy levels of the manifold of coupled translational and rotational states

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

“…The quantum T-R dynamics of HD@C 60 has been shown to differ significantly from that of the caged H 2 , on account of the mass anisotropy of HD and the significant rotational state mixing it causes [3]. The INS spectroscopy has so far provided only very limited experimental information about this interesting system [15,16]. Therefore, the predicted spectra which have emerged from this study should be very valuable for future INS investigations of HD@C 60 [17].…”

“…Therefore, in order to achieve a more realistic comparison with the measured spectra, the computed INS spectra are averaged over all possible orientations of C 60 , as described previously [18]. Moreover, with the IN4C spectrometer used by Horsewill and co-workers [16], the INS spectra of H 2 and HD in C 60 are recorded over a broad range of κ ≡ |κ| values. This means that S(κ, ω), obtained by averaging S(κ, ω) in equation (2.3) over all directions of the wavevector κ [18], needs to be integrated also over κ to obtain the desired S(ω), which is done below.…”

“…The evaluation of S(κ, ω) in equation (2.3) using the quantum five-dimensional T-R eigenstates is described in [18]. The experimental INS spectra of a hydrogen molecule in C 60 are taken from powdered samples [15,16], in which the fullerene cages are randomly oriented with respect to the incoming neutron beam. Therefore, in order to achieve a more realistic comparison with the measured spectra, the computed INS spectra are averaged over all possible orientations of C 60 , as described previously [18].…”

“…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].…”

“…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]. In their interpretation and assignment of the measured INS spectra, Horsewill and co-workers have been guided by the general theoretical framework developed by us [2,3], in particular the T-R coupling scheme, and the accurately calculated T-R energy levels of H 2 @C 60 [5].…”