RESUMEN
This paper describes the physical modelling of neutron scattering in two polycrystalline inclusion compounds, fully deuterated clathrate hydrate andC60, each with paramagnetic oxygen as guest molecules. For studying the suitability of these materials for neutron moderation to very low energies, the model includes, in addition to the magnetic neutron scattering by the oxygen, the nuclear scattering by all constituents. The theoretical total cross sections are calculated based on the phonon density of states obtained by density functional theory and molecular dynamics simulations. At low temperatures, the developed scattering kernels are in good agreement with experimental neutron scattering data reported in the literature. At 20 K and above, a Lorentzian distribution for the zero-field splitting of the magnetic substates of the spin triplet of the oxygen molecules helps to reproduce magnetic peaks observed in inelastic neutron scattering experiments better than the original theory based on a single-valued splitting constant. Neutron spectra obtained by Monte Carlo simulations in infinite media are presented, highlighting the potential use ofO2-containing fully deuterated clathrate hydrate as a neutron moderator for the production of very cold neutrons.
RESUMEN
A measurement of the reduced transition probability for the excitation of the ground state to the first 2+ state in 104Sn has been performed using relativistic Coulomb excitation at GSI. 104Sn is the lightest isotope in the Sn chain for which this quantity has been measured. The result is a key point in the discussion of the evolution of nuclear structure in the proximity of the doubly magic nucleus 100Sn. The value B(E2; 0+ â 2+) = 0.10(4) e2b2 is significantly lower than earlier results for 106Sn and heavier isotopes. The result is well reproduced by shell model predictions and therefore indicates a robust N = Z = 50 shell closure.
