Source of NMR line broadening for3He adsorbed on Grafoil

Hickernell, D. C.; Husa, D. L.; Daunt, J. G.; Piott, J. E.

doi:10.1007/bf00655621

J Low Temp Phys

1974

DOI: 10.1007/bf00655621

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Source of NMR line broadening for3He adsorbed on Grafoil

D. C. Hickernell

D. L. Husa

J. G. Daunt

et al.

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1976

1985

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Cited by 16 publications

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“…Hickernell et al (1974) measured the room temperature frequency shift of ethyl alcohol adsorbed on Grafoil with the magnetic field parallel and perpendicular to the f o i l . They used a cylindrical sample in which the normal to the Grafoil sheets was perpendicular to the axis of the cylinder.…”

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confidence: 99%

Orientational ordering of hydrogen molecules adsorbed on graphite

Kubik¹,

Hardy²,

Glättli³

1985

Can. J. Phys.

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The orientational behaviour of ortho-H2 and para-D2 molecules adsorbed on graphite has been studied by NMR from 0.3 to 12 K at coverages where the molecules form a [Formula: see text] registered lattice. We have observed that for 90% ortho-H2, the splitting of the high-temperature NMR doublet increases rapidly near 0.6 K and additional structure appears. We have identified this as a transition to the orientationally ordered pinwheel phase: one of the phases predicted by the mean field theory of Harris and Berlinsky. In contrast, the spectrum of 90% para-D2 evolves smoothly to a broad, weak structure as the temperature decreases, showing no evidence of ordering down to 0.3 K. This very different behaviour is unexpected, given that in the bulk solid both isotopes order at comparable temperatures. From the splitting of the high-temperature NMR doublets, we have deduced the crystal fields Vc and the effective quadrupole coupling constants Γ. For D2, Γ is somewhat less than the rigid lattice value, as expected in the presence of translational zero-point motion. However, for H2, Γ is anomalously small. The ortho–para conversion rates of H2 and D2 on our Grafoil substrate have also been measured.

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confidence: 99%

Orientational ordering of hydrogen molecules adsorbed on graphite

Kubik¹,

Hardy²,

Glättli³

1985

Can. J. Phys.

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Nuclear magnetic resonance of 3He adsorbed submonolayers on Grafoil and argon-coated Grafoil. I. Low coverages

Hegde

Daunt

1978

J Low Temp Phys

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Continuous-wave (cw) nuclear magnetic resonance measurements have been made at 5.SMHz of 3He adsorbed on Grafoil and on argon (monolayer)-coated Grafoil at coverages x <-0.40 (x = 1 corresponds to one monolayer), in the temperature range 0.35-4.21 K. To determine the fractional coverages, the adsorption area of the Grafoil and the monolayer coverages were determined from observations of argon and 3He adsorption isotherms. The results indicate that the adsorbed 3He is highly mobile and behaves as a two-dimensional nonideal Fermi gas. Relative magnetic susceptibilities determined from the NMR lines indicate that the onset of Fermi degeneracy is delayed by spin-independent -~He-3He interactions, as shown by the fit to the data of the quantum second virial coefficient expansion for the magnetic susceptibility. It is established that the residual (coverageindependent) linewidth is largely determined by spin-diffusion through local field gradients in voids in the Grafoil.

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Pulsed NMR study of submonolayer and multilayer 3He films adsorbed on Grafoil

Satoh

Sugawara

1980

J Low Temp Phys

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The nuclear spin relaxation times T I and T2 of submonolayer and multilayer 3He films adsorbed on Grafoil have been measured at temperatures between 1.2 and 4.2 K by a pulsed NMR technique. The T1 data for high-coverage films (solid and dense fluid phases) and the substrate registered phase are interpreted in terms of 3thermally activated vacancies. In solids the quantum exchange inherent in He is shown to be important at low temperatures. The data for multilayer films are discussed in the light of the particle exchange between layers and the relaxation time of each layer. The dynamical behavior of adatoms in the solid, fluid, and substrate registered phases as well as the nature of phase transitions between them are discussed on the basis of information obtained from the analysis of T1 and T 2 data. The present results as a whole seem to support the phase diagram determined by specific heat measurements. In addition, the nuclear susceptibility in submonolayer films has been measured by the same technique. The effect of Fermi degeneracy was not seen in the temperature range between 1.2 and 4.2 K.

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Source of NMR line broadening for3He adsorbed on Grafoil

Cited by 16 publications

References 7 publications

Orientational ordering of hydrogen molecules adsorbed on graphite

Orientational ordering of hydrogen molecules adsorbed on graphite

Nuclear magnetic resonance of 3He adsorbed submonolayers on Grafoil and argon-coated Grafoil. I. Low coverages

Pulsed NMR study of submonolayer and multilayer 3He films adsorbed on Grafoil

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