INVESTIGATION OF THE THERMAL STRUCTURE OF HELIUM II WITH THE HELP OF THE SCATTERING OF COLD NEUTRONS

Journal Article · Thu Dec 01 04:00:00 EST 1960 · Uspekhi Fiz. Nauk

DOI:https://doi.org/10.3367/UFNr.0072.196012d.0697· OSTI ID:4076229

Andronikashvili, E L

In the basis for current descriptions of the behavior of helium II lies the idea of the existence of two fundamental types of quantum thermal excitations, called phonons and rotons. A series of investigations in which the scattering of cold neutrons in liquid helium is interpreted in terms of scattering events in which a phonon or roton is created and takes up the recoil momentum is surveyed. Correlation of the neutron's energy and momentum changes occurring in the event yields a dispersion curve relating the energy and momentum of the thermal excitations. The experimental techniques and the analysis and interpretation of data are outlined. The results reproduce quite well a segment of the dispersion curve predicted by Landau. The high-momentum end of the curve (beyond the range of existing data) and its interpretation in terms of various possible forms of the behavior of unstable rotons is discussed. The possibility of the direct determination of the roton's chirality from the forward scattering cross section is discussed. Finally the temperature dependence of a series of thermodynamic functions predicted using an experimental dispersion curve is presented. The resulting curves agree remarkably well with direct measurements, except for a low-temperature discrepancy in the velocity of second sound. (TTT)

• Research Organization: Originating Research Org. not identified
• Sponsoring Organization: USDOE
• NSA Number: NSA-15-011859
• OSTI ID: 4076229
• Journal Information: Uspekhi Fiz. Nauk, Journal Name: Uspekhi Fiz. Nauk Vol. Vol: 72
• Country of Publication: Country unknown/Code not available
• Language: Russian

Related Subjects

ALLOTROPY
CROSS SECTIONS
DIAGRAMS
ENERGY
EXCITATION
HELIUM
HELIUM 4
HELIUM II
INTERACTIONS
LIQUIDS
LOW TEMPERATURE
MEASURED VALUES
MOMENTUM
PHONONS
PHYSICS
PROTONS
QUANTUM MECHANICS
RECOILS
SCATTERING
SECOND SOUND
SOUND
TEMPERATURE
THERMAL NEUTRONS
THERMODYNAMICS
VELOCITY