Polarization limits in K-Rb spin-exchange mixtures

Lancor, Brian; Walker, Thad

doi:10.1103/physreva.83.065401

Cited by 19 publications

(16 citation statements)

References 13 publications

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“…where we've assumed pumping with perfectly monochromatic light with frequency ν. Measurements by Romalis et al [20] and more recently by Lancor et al [31][32][33] indicate that |T d | is of order 0.1 ps for alkali-3 He collisions. Using this value, we find that (3σ 3 .…”

Section: The Alkali X-factorsmentioning

confidence: 99%

Development of high-performance alkali-hybrid polarizedHe3targets for electron scattering

et al. 2015

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We present the development of high-performance polarized 3 He targets for use in electron scattering experiments that utilize the technique of alkali-hybrid spin-exchange optical pumping. We include data obtained during the characterization of 24 separate target cells, each of which was constructed while preparing for one of four experiments at Jefferson Laboratory in Newport News, Virginia. The results presented here document dramatic improvement in the performance of polarized 3 He targets, as well as the target properties and operating parameters that made those improvements possible. Included in our measurements were determinations of the so-called X-factors that quantify a temperature-dependent and as-yet poorly understood spin-relaxation mechanism that limits the maximum achievable 3 He polarization to well under 100%. The presence of this spinrelaxation mechanism was clearly evident in our data. We also present results from a simulation of the alkali-hydrid spin-exchange optical pumping process that was developed to provide guidance in the design of these targets. Good agreement with actual performance was obtained by including details such as off-resonant optical pumping. Now benchmarked against experimental data, the simulation is useful for the design of future targets. Included in our results is a measurement of the K-3 He spin-exchange rate coefficient k K se = (7.46 ± 0.62)×10 −20 cm 3 /s over the temperature range 503 K to 563 K.

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Section: The Alkali X-factorsmentioning

confidence: 99%

Development of high-performance alkali-hybrid polarizedHe3targets for electron scattering

et al. 2015

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“…At other regimes, SE collisions can be utilized to incoherently transfer polarization between different atomic states [10,11], as is widely used in the production of hyper-polarized noble gases for medical imaging [12], spin-polarized targets [13], and precision measurements [14,15]. The incoherent transfer of polarization via SE collisions was also demonstrated in a hybrid system of two alkali species [16,17], improving magnetometery sensitivity by optically pumping one specie at a given optical-depth and monitoring the other [18]. However, the coherent effects of the SE collisional interaction between different species of alkali atoms have never been investigated.In this Letter, we demonstrate a coherent coupling of two alkali species, potassium (K) and rubidium (Rb), induced by random SE collisions.…”

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confidence: 99%

Coherent Coupling of Alkali Atoms by Random Collisions

2015

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Random spin-exchange collisions in warm alkali vapor cause rapid decoherence and act to equilibrate the spin state of the atoms in the vapor. In contrast, here we demonstrate experimentally and theoretically a coherent coupling of one alkali species to another species, mediated by these random collisions. We show that the minor species (potassium) inherits the magnetic properties of the dominant species (rubidium), including its lifetime (T_{1}), coherence time (T_{2}), gyromagnetic ratio, and spin-exchange relaxation-free magnetic-field threshold. We further show that this coupling can be completely controlled by varying the strength of the magnetic field. Finally, we explain these phenomena analytically by mode mixing of the two species via spin-exchange collisions.

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“…10). This comes from off-resonant pumping of the K atoms by the resonant Rb light (Lancor and Walker, 2011) and limits the useful density ratios to 𝒟 < 10. Chen et al (2007b) observed similar results and found that the polarization decline was not observed if hybrid cells were optically pumped with 770 nm light.…”

Section: Spin-exchange Optical Pumpingmentioning

confidence: 99%

“…Finally, even for narrow band pumping hybrid K:Rb mixtures exhibit reduced maximum polarizations at high 𝒟 due to off-resonant absorption of the Rb pumping light by the K atoms (Lancor and Walker, 2011), see Fig 10. This effect limits the useful values of 𝒟 <10.…”

Section: Spin-exchange Optical Pumpingmentioning

confidence: 99%

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Optically polarizedHe3

et al. 2017

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This article reviews the physics and technology of producing large quantities of highly spin-polarized 3He nuclei using spin-exchange (SEOP) and metastability-exchange (MEOP) optical pumping. Both technical developments and deeper understanding of the physical processes involved have led to substantial improvements in the capabilities of both methods. For SEOP, the use of spectrally narrowed lasers and K-Rb mixtures has substantially increased the achievable polarization and polarizing rate. For MEOP nearly lossless compression allows for rapid production of polarized 3He and operation in high magnetic fields has likewise significantly increased the pressure at which this method can be performed, and revealed new phenomena. Both methods have benefitted from development of storage methods that allow for spin-relaxation times of hundreds of hours, and specialized precision methods for polarimetry. SEOP and MEOP are now widely applied for spin-polarized targets, neutron spin filters, magnetic resonance imaging, and precision measurements.

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Polarization limits in K-Rb spin-exchange mixtures

Abstract: We present measurements of the optical absorption of K vapor at 795 nm due to the presence of high-pressure He gas. The results set a limit on the polarization attainable in hybrid spin-exchange optical pumping of 3 He.

Cited by 19 publications

References 13 publications

Development of high-performance alkali-hybrid polarizedHe3targets for electron scattering

Development of high-performance alkali-hybrid polarizedHe3targets for electron scattering

Coherent Coupling of Alkali Atoms by Random Collisions

Optically polarizedHe3

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