Spin rotation effects and spin waves in gaseous 3He↑

Nacher, Pierre-Jean; Tastevin, Geneviève; Leduc, Michèle; Crampton, S. B.; Laloë, Franck

doi:10.1051/jphyslet:01984004509044100

Cited by 72 publications

(30 citation statements)

References 17 publications

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“…Spin waves in dilute gases were predicted at the beginning of the eighties [1,2] and confirmed experimentally soon after [3,4,5]. They can be understood in two equivalent ways, either as a consequence of spin mean field [1], or in more microscopic terms as the cumulative result of the identical spin rotation effect (ISRE) -an effect taking place during binary collisions between identical atoms [2].…”

Section: Pacs Numbersmentioning

confidence: 99%

Cumulative Identical Spin Rotation Effects in Collisionless Trapped Atomic Gases

2009

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We discuss the strong spin segregation in a dilute trapped Fermi gas recently observed by Du et al. with "anomalous" large time scale and amplitude. In a collisionless regime, the atoms oscillate rapidly in the trap and average the inhomogeneous external field in an energy dependent way, which controls their transverse spin precession frequency. During interactions between atoms with different spin directions, the identical spin rotation effect (ISRE) transfers atoms to the up or down spin state, depending on their motional energy. Since low energy atoms are closer to the center of the trap than high energy atoms, the final outcome is a strong correlation between spins and positions. PACS numbers:Spin waves in dilute gases were predicted at the beginning of the eighties [1, 2] and confirmed experimentally soon after [3,4,5]. They can be understood in two equivalent ways, either as a consequence of spin mean field [1], or in more microscopic terms as the cumulative result of the identical spin rotation effect (ISRE) -an effect taking place during binary collisions between identical atoms [2]. Similarly, the Faraday effect is a rotation of the spin of photons that can be seen, either as a consequence of a macroscopic index of refraction, or as resulting from the accumulation of microscopic forward scattering events between photons and atoms.Experiments with ultracold atomic gases have renewed the interest in spin waves. In 2002, a group at JILA [6] showed that, in an trapped ultracold atomic gas of bosons, the ISRE can result in a spontaneous spatial "segregation" of two atomic internal states |1 and |2 (equivalent to a pseudo-spin 1/2). Several groups then proposed a theoretical explanation of these observations, using either one-dimensional spin 1/2 hydrodynamic [7] or kinetic [8,9] equations. More recently, Du et al. from Duke University [10] did an experiment that explores the properties of spin waves in quantum gases of fermions ( 6 Li) in the collisionless Knudsen regime, while most previous experiments were performed in the hydrodynamic regime (see nevertheless [11]). The spin segregation they observe is a hundred times larger and a hundred times slower than would be predicted by hydrodynamic theory. They call this spectacular effect "anomalous spin segregation" and suggest that its explanation may require "a modification of spin wave theory or possibly a new mechanism" for fermions.The purpose of this letter is twofold. First we argue that no modification of spin wave theory is necessary to understand the experiment; the physical mechanism behind the observations is the usual ISRE. The difference between bosons and fermions is not essential; what is important is the collisionless regime. Second, we discuss why this collisionless regime, combined with the presence of a trap, gives access to unexpected and interesting new physics. In fact, one can observe the ISRE almost as in an ideal experiment, where a single spin polarized atom is sent through a target of a gas polarized in another direction, and where t...

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Section: Pacs Numbersmentioning

confidence: 99%

Cumulative Identical Spin Rotation Effects in Collisionless Trapped Atomic Gases

2009

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“…Recently, several experiments on spin waves in dilute, non-degenerate systems have been reported, in the case of HT [8,9], of very dilute solutions of 3Hei in superfluid 4He (where the 'He-atoms behave very similarly to a real gas) [10] and 3 HeT [11]. Those Figure I gives a schematic view of the situation : two pairs of coils, each in opposition, are mounted around a spherical sample.…”

Section: Physics Abstractsmentioning

confidence: 99%

“…The experimental set-up is very similar to that described previously [11], except for the NMR coils which are set as described in the preceding paragraph. Optical pumping with a laser creates nuclear polarization in a gas at room temperature, while gas diffusion through a long glass pipe transfers the nuclear polarization to a second cell at liquid helium temperatures; in the lower part of the system, solid hydrogen is used as a cryogenic coating to suppress the strong nuclear relaxation which would be produced by bare glass walls at a few degrees Kelvin where the transverse magnetization never exceeds a small fraction ( 10 %) of the longitudinal one, so that a linearized spin diffusion theory [3,8,9] can be used.…”

Section: Physics Abstractsmentioning

confidence: 99%

“…On the other hand, the magnetic gradients are reduced with the help of superconducting shielding and sets of coils creating pure gradients of the longitudinal static field, as described in reference [11]; the motional narrowing conditions are fulfilled and in practice, values of T2 ranging from 1 s to 10 s, or more, are accessible. It is therefore not difficult to distinguish,between the spin wave signal and a possible spurious signal due to the total transverse magnetization of the sample, which would decay with a much longer time constant (2) The diffusion modes corresponding to higher n or I values also contribute to the signal, but only weakly (see the Appendix of Ref.…”

Section: Physics Abstractsmentioning

confidence: 99%

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Direct detection of spin waves in gaseous 3He↑

et al. 1985

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“…But only limited polarization (of order 1%) could be obtained due to fast wall relaxation. It was only with the use of non-relaxing cryogenic coatings providing long T 1 s [57] that polarized 3 He could be successfully cooled as a highly polarized gas, or liquid [58], allowing for instance studies of the effect of spin-polarization on quantum properties of gaseous 3 He [59,60]. This series of studies in dense polarized systems obtained by cryogenic methods is currently focused on the non-linear NMR behavior that results from the action of distant dipolar fields in hyperpolarized liquids [61].…”

Section: Hyperpolarization Of Noble Gasesmentioning

confidence: 99%

Magnetic Resonance Imaging: From Spin Physics to Medical Diagnosis

Nacher

2009

The Spin

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Abstract. Two rather similar historical evolutions are evoked, each one originating in fundamental spin studies by physicists, and ending as magnetic resonance imaging (MRI), a set of invaluable tools for clinical diagnosis in the hands of medical doctors. The first one starts with the early work on nuclear magnetic resonance, the founding stone of the usual proton-based MRI, of which the basic principles are described. The second one starts with the optical pumping developments made to study the effects of spin polarization in various fundamental problems. Its unexpected outcome is a unique imaging modality, also based on MRI, for the study of lung physiology and pathologies.

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Spin rotation effects and spin waves in gaseous 3He↑

Cited by 72 publications

References 17 publications

Cumulative Identical Spin Rotation Effects in Collisionless Trapped Atomic Gases

Cumulative Identical Spin Rotation Effects in Collisionless Trapped Atomic Gases

Direct detection of spin waves in gaseous 3He↑

Magnetic Resonance Imaging: From Spin Physics to Medical Diagnosis

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