Experimental studies of the excitation spectrum of /sup 3/He--/sup 4/He mixtures using neutron inelastic scattering

Journal Article · Wed Jun 01 04:00:00 EDT 1977 · J. Low Temp. Phys.; (United States)

DOI:https://doi.org/10.1007/BF00655711· OSTI ID:7219637

Hilton, P A; Scherm, R; Stirling, W G

Neutron inelastic scattering techniques have been used to study the excitation spectrum of mixtures containing 6%, 12%, and 25% of /sup 3/He in /sup 4/He at 0.75 K. The 6% mixture has also been investigated at temperatures of 0.6, 1.0, and 1.5 K. The measurements have been made in the wave-vector transfer range Q=0.8--2.3A/sup -1/. The energy spectra observed contain two principal features, which are interpreted as scattering from (a) phonon--roton excitations arising from the /sup 4/He, and (b) quasiparticle--quasihole excitations arising from the /sup 3/He. In the dilute /sup 3/He--/sup 4/He mixture, our results indicate a /sup 3/He particle--hole continuum which deviates from the quadratic form, proposed by Landau and Pomeranchuk, and which lies below the /sup 4/He phonon--roton dispersion curve. However, we are unable to say whether or not the continuum exhibits a minimum as a function of energy, as has recently been proposed by several authors, because we were unable to resolve the scattering from the particle--hole continuum for Q9 or approx. =1.7A/sup -1/. In this region of Q space the energy spectra are dominated by the roton excitations. We have also determined the shifts in energy and increases in linewidth of the phonon--roton excitations relative to those of pure /sup 4/He and compared these measurements to several theoretical predictions.

• Research Organization: University of Edinburgh, U.K.
• OSTI ID: 7219637
• Journal Information: J. Low Temp. Phys.; (United States), Journal Name: J. Low Temp. Phys.; (United States) Vol. 27:5; ISSN JLTPA
• Country of Publication: United States
• Language: English

Related Subjects

640450* -- Fluid Physics-- Superfluidity
640460 -- Fluid Physics-- Other Quantum Fluids
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COHERENT SCATTERING
DIFFRACTION
ENERGY SPECTRA
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HELIUM 3
HELIUM 4
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
NEUTRON DIFFRACTION
NUCLEI
PHONONS
QUANTITY RATIO
QUASI PARTICLES
ROTONS
SCATTERING
SPECTRA
STABLE ISOTOPES
SUPERFLUIDITY