Nuclear Magnetic Spin–Lattice Relaxation in Solid Deuterium below Tλ

Smith, M; White, D. R.; Gaines, J. R.

doi:10.1063/1.1670588

Cited by 14 publications

(2 citation statements)

References 8 publications

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“…As previously shown, the kinetic model predicts two measurable relaxation times differing widely in magnitude, Eq. (22). This is what is observed experimentally and as shown elsewhere 32 provides a basis for precise orth()-'para analysis from the measurements of the spin amplitude ratio SoC 00 ) / Sp( 00 ).…”

Section: The Liquidsupporting

confidence: 77%

Nuclear Spin—Lattice Relaxation in Ortho—Para Mixtures of Solid and Liquid Deuterium

Wang

Smith

White

1971

The Journal of Chemical Physics

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A comprehensive study of the nuclear spin-lattice relaxation in the hexagonal close packed phase of solid deuterium and the liquid is presented. All of the measurements covering the temperature range 2.S-20.3°K and for para concentration 2%-94% were carried out using a pulsed technique, the pulse sequence being saturation -T-90° at 8.0 MHz. It is shown that all of the experimental data can be accounted for on the basis of a kinetic model which assumes three principal relaxation mechanisms for the transfer of spin energy to the lattice from the two spin systems 1=1, J = 1 (para-D2) and 1=2, J =0 (ortho-D2). These are (1) the modulation of the intramolecular spin-spin interactions by the anisotropic electric quadrupolar intermolecular interactions which represents the most important process for the direct relaxation of para-D2, (2) the intermolecular spin-spin interaction modulated by the self-diffusion in the solid or liquid which represents the only direct process for relaxation of the ortho-D2, and (3) the adiabatic cross relaxation between the two spin systems, the indirect process for the relaxation of the ortho-D2 dependent on the extent of coupling between the two different spins. This varies from the extreme of strong coupling in the rigid solid, where the self-diffusion is negligible, to weak coupling in the high-temperature solid and liquid where thermal motion is significant. A quantitative explanation of the experimental results for the hexagonal close packed solid is given in terms of existing theories for the mechanisms mentioned above. For the rigid solid regime (up to approximately 14°K), where the relaxation is determined entirely by the first mechanism, this requires that an effective electric quadrupole coupling constant in the solid of from O.SS to 0.62ro be the coupling constant for the isolated pair. In the diffusion dominated regime, 14°K to the triple point all three mechanisms play an important role. Excellent agreement between theory and experiment is obtained for the same r eff, a self-diffusion coefficient Do=9.0SX 10-2 cm 2 /sec and an activation energy Ea =667 cal/mole, except for solids of very low para concentration. For the latter Do= 2.0X 10-2 cm 2 /sec and Ea=608 cal/mole. The theory predicts the observed frequency dependence of the spin-lattice relaxation in the diffusion-dominated regime. In the liquid state a spin-lattice relaxation time can be separately identified for each spin system. Whereas the para-D2 (l = 1, J = 1) results can be accounted for on a model which assumes mechanism (1) modified by the thermal motion in the liquid, no simple explanation is possible for the ortho-D 2 data.

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Section: The Liquidsupporting

confidence: 77%

Nuclear Spin—Lattice Relaxation in Ortho—Para Mixtures of Solid and Liquid Deuterium

Wang

Smith

White

1971

The Journal of Chemical Physics

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“…The increase in T1-l with decreasing temperature in the "paramagnetic" regime was observed in H2 by Amstutz et al 43 The anomalous increase in Tl at the transition, indicated by Eq. (22) has been observed by Smith et al 44 in D2•…”

Section: Nuclear Spin-lattice Relaxation Ratessupporting

confidence: 51%

Solid Hydrogen: The Ideal Analog of an Antiferromagnet

Harris

1971

Journal of Applied Physics

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A physically meaningful analogy is drawn between the ordering and dynamical behavior of molecular rotations in solid hydrogen and the ordering and dynamical behavior of magnetic spin systems. In solid hydrogen the magnitude J of the rotational angular momentum is a good quantum number. Molecules having J = 1 resemble spin one magnetic moments, whereas those with J = 0 are "non-magnetic." Solid solutions of these two species are analogs of magnetic alloys. The thermodynamic properties, in particular the order parameter, the specific heat, and the nuclear magnetic resonance properties are similar to those of magnetic systems. As for the dynamics, the small librations about the ground state are analogs of spin waves, and the interactions between the librational excitations are similar to, but larger than, the usual spin-wave interactions. This circumstance enables the direct observation of the two-libron spectrum and also leads to large anharmonic shifts in the single-libron spectrum. Disciplines PhysicsThis journal article is available at ScholarlyCommons: http://repository.upenn.edu/physics_papers/440 Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104A physically meaningful analogy is drawn between the ordering and dynamical behavior of molecular rotations in solid hydrogen and the ordering and dynamical behavior of magnetic spin systems. In solid hydrogen the magnitude J of the rotational angular momentum is a good quantum number. Molecules having J = 1 resemble spin one magnetic moments, whereas those with J =0 are "nonmagnetic." Solid solutions of these two species are analogs of magnetic alloys. The thermodynamic properties, in particular the order parameter, the specific heat, and the nuclear magnetic resonance properties are similar to those of magnetic systems. As for the dynamics, the small librations about the ground state are analogs of spin waves, and the interactions between the librational excitations are similar to. but larger than. the usual spin-wave interactions. This circumstance enables the direct observation of the two-Iibron spectrum and also leads to large anharmonic shifts in the single-Iibron spectrum.

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Orientational ordering in solid D2 from NMR studies. I. The hcp phase

Calkins

Banke

et al. 1986

J Low Temp Phys

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Nuclear Magnetic Spin–Lattice Relaxation in Solid Deuterium below Tλ

Cited by 14 publications

References 8 publications

Nuclear Spin—Lattice Relaxation in Ortho—Para Mixtures of Solid and Liquid Deuterium

Nuclear Spin—Lattice Relaxation in Ortho—Para Mixtures of Solid and Liquid Deuterium

Solid Hydrogen: The Ideal Analog of an Antiferromagnet

Orientational ordering in solid D2 from NMR studies. I. The hcp phase

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