Neutron scattering from superfluid helium at large momentum transfers. [1. 2 K]

Journal Article · Sat May 01 00:00:00 EDT 1976 · J. Low Temp. Phys.; (United States)

DOI:https://doi.org/10.1007/BF00116921· OSTI ID:7338831

Martel, P ^[1]; Svensson, E C; Woods, A D.B.; Sears, V F; Cowley, R A

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1. Atomic Energy of Canada Ltd., Chalk River, Ont.

The inelastic scattering of thermal neutrons from liquid helium at 1.2 K has been measured for wave-vector transfers in the range 6.0 less than or equal to Q less than or equal to 12.0 A/sup -1/. Oscillations in the widths of the scattered-neutron distributions as a function of Q are observed to persist at least up to 12.0 A/sup -1/. A simple physical model suggests that these oscillations, which reflect the presence of final-state interactions and interference effects, have their origin in similar oscillations which occur in the He--He scattering cross section. Detailed measurements at Q = 10.0 A/sup -1/ show no evidence of a well-defined condensate peak, and calculations suggest that Q values in the range 50--100 A/sup -1/ or greater may be required to observe a separate condensate component in the line shape. A method is developed for eliminating a major part of the effects of final-state interactions from the Doppler part of the distributions, and the corrected data at Q = 10.0 A/sup -1/ are analyzed to determine the momentum distribution in liquid helium at 1.2 K. The resulting distribution is found to be non-Gaussian with a well-defined high-momentum tail. The result is compared with the momentum distribution obtained recently by Mook from thermal neutron time-of-flight data near Q = 15 A/sup -1/ and with theoretical calculations of McMillan and of Kalos.

• OSTI ID: 7338831
• Journal Information: J. Low Temp. Phys.; (United States), Vol. 23:3/4
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
HELIUM II
NEUTRON TRANSPORT
DISTRIBUTION
FINAL-STATE INTERACTIONS
INELASTIC SCATTERING
INTERFERENCE
LINEAR MOMENTUM TRANSFER
OSCILLATIONS
THERMAL NEUTRONS
BARYONS
ELEMENTARY PARTICLES
EVEN-EVEN NUCLEI
FERMIONS
HADRONS
HELIUM 4
HELIUM ISOTOPES
INTERACTIONS
ISOTOPES
LIGHT NUCLEI
NEUTRAL-PARTICLE TRANSPORT
NEUTRONS
NUCLEI
NUCLEONS
RADIATION TRANSPORT
SCATTERING
STABLE ISOTOPES
640450* - Fluid Physics- Superfluidity
654003 - Radiation & Shielding Physics- Neutron Interactions with Matter