Nuclear magnetic susceptibility of3He adsorbed on graphite below 4.2 K

Grimmer, D. P.; Luszczynski, K.

doi:10.1007/bf00654557

Cited by 17 publications

(3 citation statements)

References 28 publications

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“…13 The same analysis applied to the data on the thick 3He film on Grafoil gives D, = 5 x 10 .5 cmZ/sec at 1.3 K, with a = 1.0 txm and o-= 8 x 10 -5. In this film, which is some 80 monolayers thick and which occupies about 20% of void volume in Grafoil, D~ is found to be very close to the value for the bulk liquid, as expected.…”

Section: He On Grafoilmentioning

confidence: 99%

“…Measurements of the nuclear magnetic susceptibility for 3He on Grafoil are presented and discussed elsewhere. 13 There are several general reviews of nuclear spin relaxation studies on molecules adsorbed on various substrates. 14,15 Of particular interest in these studies are questions relating to migration of molecules between different adsorbed states, anisotropic motion, and distribution of correlation times.14 Interpretation of NMR measurements in these systems is usually complicated by the relatively strong interactions between the adsorbed layer and the substrate, whose specific properties and surface impurities can in fact dominate the behavior of the adsorbed layer.…”

Section: Introductionmentioning

confidence: 99%

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NMR Relaxation times of 3He adsorbed on graphite below 4.2 K

Grimmer

Luszczynski

1978

J Low Temp Phys

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Pulsed NMR measurements were performed at 10 and 20 MHz on thin 3He films on graphitic surfaces in the temperature range between 0. 35 and 4.2 K. Most of the measurements reported here have been obtained with basal-planeoriented graphite (Grafoil) outgassed izt 130~ but in some experiments graphitized carbon black powder (Sterling b-T), vacuum-baked at 1100~ was used for comparison. The aHe coverages examined range from O. 1 to 80 monolayers on Grafoil and from 0.3 to 1.0 monolayers on Sterling FT. Measurements have also been made on 3He-4He films on Grafoil with one-monolayer quantity of 3He mixed with various amounts of 4He. The measured free-induction decay time T~, the spin-echo decay time T+2, and the spin-lattice relaxation time T1 suggest that the observed relaxation phenomena in 3He are largely governed by the 3He-substrate interaction. In 3 "~ r the case of He on Grafoil, T2 is much longer than T2, evidently as a result of large local magnetic field gradients and significant lateral mobility of 3He on this substrate. These results, in con]unction with a simple model of spin diffusion in restricted ~eometries, lead to values of the diffusion coefficient Ds of about 2.1 xlO-Scm /sec at 4.2K and 7.0xlO-6cm2/sec at 1.2K for one-monolayer coverages; these values of Ds are indicative of a nonlocalized 3He system. To verify the model used, the restricted diffusion analysis was applied to room-temperature measurements on C6F6 in Grafoil ; the values of the diffusion coefficient obtained in this way are in good agreement with diffusion rates measured directly in bulk liquid C6F6 at room temperature. In 3 t the case of He on Sterling FT, the restricted diffusion analysis of the T2 data gives Ds-~2 • lO-S cmZ/sec for 0.6 monolayer of 3He; this value of Ds suggests a relatively localized system. The measured T'2 is found to decrease monotonically with coverage and there is no evidence of any phase transition in 3He films for coverages up to one monolayer.

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Section: He On Grafoilmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

NMR Relaxation times of 3He adsorbed on graphite below 4.2 K

Grimmer

Luszczynski

1978

J Low Temp Phys

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“…The principal motivation for this paper was the quantitative analysis of data on nuclear magnetic susceptibility in 3He monolayers adsorbed on graphite below 4.2 K. 2 The data indicated a non-Curie behavior of the form that could be described by an ideal twodimensional Fermi-Dirac gas. The ideal-gas model is used here mainly as an aid in data analysis and its use does not imply that 3He atoms in monolayers behave as noninteracting particles.…”

Section: Introductionmentioning

confidence: 99%

The quantitative application of Fermi-Dirac functions to two- and three-dimensional systems

1981

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Expressions for the various physical parameters of the ideal Fermi-Dirac gas in two dimensions are derived and compared to the corresponding threedimensional expressions. These derivations show that the Fermi-Dirac functions most applicable to the two-dimensional problem are Fo(*7), FI(.7), and F~o(*7). Analogous to the work of McDougall and Stoner in three dimensions, these functions and parameters derived from them are tabulated over the range of the argument, -4 <_ '7 <-20. The physical applications of the tabulated 2D and 3D functions to 3He monolayer and bulk liquid 3He nuclear magnetic susceptibilities, respectively, are considered. Calculational procedures of fitting data to theoretical parameters and criteria for judging the quality of fit of data to both two-and three-dimensional Fermi-Dirac values are discussed.

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Nuclear Magnetic Resonance in Adsorbed Helium

Richards

1980

Phase Transitions in Surface Films

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Nuclear magnetic susceptibility of3He adsorbed on graphite below 4.2 K

Cited by 17 publications

References 28 publications

NMR Relaxation times of 3He adsorbed on graphite below 4.2 K

NMR Relaxation times of 3He adsorbed on graphite below 4.2 K

The quantitative application of Fermi-Dirac functions to two- and three-dimensional systems

Nuclear Magnetic Resonance in Adsorbed Helium

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