/sup 3/He-/sup 19/F interaction at the surface of fluorocarbon polymers
The interaction between /sup 19/F nuclear spins in Teflon and /sup 3/He spins on its surface has been studied in magnetic fields up to 6 Tesla. At temperatures below 1 K, a monolayer of /sup 3/He is sufficient to increase the NMR relaxation rate of /sup 19/F more than an order of magnitude over the value with vacuum or with a coverage of pure /sup 4/He. With a DLX 6000 substrate, the coupling between the two nuclear species weakens towards 6 T. With an Aldrich substrate, the coupling is still active, but it was not observed that the magnetization of a /sup 3/He film follows that of /sup 19/F substrate spins. In monolayer experiments, the field dependence of the fluorine nuclear relaxation time T/sub 1F/ is stronger than a quadratic law above 2.5 T, while with liquid /sup 3/He this field dependence is reduced to a linear law. Most of the data are discussed in terms of a coupling model, in which the /sup 19/F-/sup 3/He nuclear dipolar interaction is modulated by motion of /sup 3/He atoms. The temperature dependence for T/sub 1F/ points to mechanisms involving vacancies, mass fluctuations or exchange inside the /sup 3/He surface layer or, in one case, paramagnetic centers, in the /sup 3/He-/sup 19/F coupling. The relaxation time of the fluorine dipolar reservoir in the Aldrich substrate is of the order of minutes at 3 K and 2.5 T, even in the presence of /sup 3/He.
- Research Organization:
- H.C. Oersted Institute, Copenhagen (Denmark)
- OSTI ID:
- 5841568
- Journal Information:
- J. Low Temp. Phys.; (United States), Vol. 74:5-6
- Country of Publication:
- United States
- Language:
- English
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SUPERCONDUCTIVITY AND SUPERFLUIDITY
FLUORINE 19
J-J COUPLING
HELIUM 3
TEFLON
NUCLEAR MAGNETIC RESONANCE
ELECTRON SPIN RESONANCE
FILM FLOW
MAGNETIC DIPOLES
MAGNETIC FIELDS
MAGNETIZATION
MATHEMATICAL MODELS
PARAMAGNETISM
RELAXATION TIME
SCANNING ELECTRON MICROSCOPY
SPIN
SPIN-SPIN RELAXATION
SUBSTRATES
SUPERFLUIDITY
SURFACES
TEMPERATURE DEPENDENCE
ULTRALOW TEMPERATURE
VACANCIES
ANGULAR MOMENTUM
COUPLING
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DIPOLES
ELECTRON MICROSCOPY
EVEN-ODD NUCLEI
FLUID FLOW
FLUORINATED ALIPHATIC HYDROCARBONS
FLUORINE ISOTOPES
HALOGENATED ALIPHATIC HYDROCARBONS
HELIUM ISOTOPES
INTERMEDIATE COUPLING
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MAGNETISM
MATERIALS
MICROSCOPY
MULTIPOLES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PARTICLE PROPERTIES
PETROCHEMICALS
PETROLEUM PRODUCTS
PLASTICS
POINT DEFECTS
POLY
POLYETHYLENES
POLYTETRAFLUOROETHYLENE
RELAXATION
RESONANCE
STABLE ISOTOPES
SYNTHETIC MATERIALS
640450* - Fluid Physics- Superfluidity
656002 - Condensed Matter Physics- General Techniques in Condensed Matter- (1987-)