Time: 10:00
Venue: KFKI Campus, Building 1. Seminar room

Speaker: Matthew Krzystyniak (ISIS,STFC,RAL)

ABSTRACT

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.