Seminar on "Mass-resolved neutron spectroscopy"
Venue: KFKI Campus, Building 1. Seminar room
Speaker: Matthew Krzystyniak (ISIS,STFC,RAL)
Neutron Compton scattering (NCS) is a unique experimental technique made possible by the development of epithermal neutron sources, such as the ISIS source of the Rutherford Appleton Laboratory in the UK. The measurement of nuclear momenta by high-energy neutron Compton scattering relies on the fact that the energy and momentum transferred in the scattering process are sufficiently large, such that the so-called impulse approximation (IA) is an accurate starting point. In the IA limit, the dynamic structure factor measured in NCS for a given nucleus covers the whole energy range of its motional modes. This includes translational and rotational modes, followed by lattice and internal molecular vibrations.
Since its birth, the NCS technique has been employed to study proton momentum distributions in quantum ﬂuids and solids, metal hydrides and gas and charge-storage media, etc. Beyond the proton, recent instrument developments towards MANSE (Mass-resolved Neutron Spectroscopy) offer the prospects of access to the NMDs of heavier nuclides including deuterium, helium, lithium, carbon, oxygen, and ﬂuorine.
I will present some examples of recent MANSE work advocating an unprecedented combination of ab initio tools and neutron scattering techniques employed for the first time in the context of the characterisation of nuclear quantum chemical dynamics in the solid state with the special emphasis on hydrogen bonded molecular crystals.
Keywords: Neutron Compton scattering; nuclear momentum distribution; periodic DFT, Born Oppenheimer Molecular Dynamics, hydrogen bonded molecular crystals.