Kinetic energy and momentum distribution spectroscopy with eV - PowerPoint PPT Presentation

Kinetic energy and momentum distribution spectroscopy with eV neutrons Microscopic dynamics of quantum fluids within the e.VERDI Project at ISIS � Roberto Senesi � Roma, 6 –5-2004

� Why and n p ( ) KE � Distribution functions � Radial distribution are key quantities for function: microscopic the microscopic occupation probability description of in r-space condensed systems � Momentum distribution function: microscopic occupation probability in p-space

� and KE n p ( ) � Contain information � They do not give on the average direct information on instantaneous collective and dynamics single-particle excitations but reflect the properties of many-body condensed systems

Quantum statistical mechanics: no general results � n p ( ) KE � and � Ad hoc descriptions � n p ( ) of for Bosons, are always greater (broader) than the classical values, fermions etc. because of: � Wigner-Kirkwood � zero-point motion perturbative [x,p]=i � Heisemberg approach limited to principle almost-classical � Bogoliubov inequality systems (Landau interacting systems book), such as liquid density dependence and solid Ne.

Systems studied: � Atomic electrons � Degenerate (Du Mond -1929) ultracold atomic gases � Nucleons in nuclei, etc (ref. West � Liquid Helium-s , scaling variable) Mixtures, Quantum solids � Neutron matter � Molecular systems � Nucleons

velocity distribution of a cloud of rubidium atoms at (a) just before the appearance of the Bose-Einstein condensate, (b) just after the appearance of the condensate and (c) after further evaporation left a sample of nearly pure condensate

� KE and spectroscopy of n p ( ) quantum fluids and solids: Deep Inelastic Scattering of eV Neutrons Scattering in the Impulse Approximation: when a He atom recoils freely The atom’s velocity before 2 q � � High energy -high momentum ∆ = + ⋅ E v q scattering event can i 2 M neutron scattering be measured! VESUVIO spectrometer at ISIS

Longitudinal Compton Profile Analysis � Desiderata: � The analysis and interpretation of the The spectrometer lineshape of the response must be recoil peak give (much) narrower access to and than n(p)! KE � n p ( )

open problems � Quantitative description of � “Fermiology”: does Density and Temperature liquid 3 He have a dependence : fermionic lineshape? 3 = + ρ KE k T f ( , T ) B 2 � Dependence on the state of aggregation: liquid-solid discontinuity

open problems-continued � Kinetic energy reduction in � Breakup of the density- interacting quantum systems! dependence in liquid helium mixtures? 25 20 <T> 3 (n) [K] 15 10 5 16 18 20 22 24 26 -3 ] Atomic density n [nm

open problems-continued � Does helium in narrow � Supersolid He in VYCOR channels (xerogels, nanotubes, etc) show axial confinement? ZSM-5 zeolite. The cavity and channel structure seen by Argon atoms.

open problems-continued � Kinetic energy in strong quantum solids 3 He 4 He

Research activity on Quantum Fluids within the e.VERDI project � Kinetic energy of � Kinetic energy of helium in xerogel He-Ne mixtures � Kinetic energy of � Accurate momentum solid 3 He distribution of 3 He � Kinetic energy of helium mixtures across the liquid- solid boundary

Research activity on Quantum Fluids within the e.VERDI project Resolution improvements � High quality data with have been accomplished within VESUVIO project improved resolution by fine analysis of neutron energy after scattering event

Research activity on Quantum Fluids within the e.VERDI project Energy Selector (resonant foil)+ Velocity Selector (veto on transit time) Resolution narrowing with respect to VESUVIO