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Poster Session

Poster Session III

4:00 pm – 6:00 pm, Thursday June 19 Session S00 Oregon Convention Center:, Exhibit Hall E
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Spin-exchange optical pumping of 129Xe in the low-pressure regime

Poster 8
Presenter: Brian Timothy Saam (Washington State University)
Authors: Chelsea Weaver (Washington State University), Eleanor Terry-Welsh (Washington State University)

Hyperpolarized noble gases, produced via spin-exchange optical pumping (SEOP), have many applications including magnetic resonance imaging, magnetometry, and spin-polarized targets. Despite decades of research, several questions remain open in SEOP of 129Xe : van der Waals (vdW) molecules (e.g., RbXe) cause the spin-exchange rate coefficient kse to have a complicated dependence on gas density and composition, both of which affect the distribution of molecular lifetimes. The regime of low total gas density (≤ 0.1 amagat) has not been further explored since initial work by Happer and coworkers almost 40 years ago [1], likely because the narrow D1 absorption line in this regime is not suited to the high-power broadband diode lasers used for most applications. While kse is certainly larger at low density due to longer-lived vdW molecules, it has neither been fully characterized in this regime nor compared to alkali-metal spin-destruction rates to determine spin-exchange efficiency. There are also open questions concerning the molecular formation mechanism(s), whether there is an “X-factor” limit to the achievable 129Xe polarization, as has been observed with 3He SEOP [2], and the dependence of kse on magnetic field. We have undertaken a systematic experimental study of kse focused on this low-density regime employing multiple experimental techniques refined over the last several years, including the frequency-shift of the alkali-metal electron paramagnetic resonance (EPR) to determine the 129Xe polarization and direct measurements of alkali-metal density and polarization. We can measure kse up to three different ways under similar conditions to root out systematic errors and possibly to account for unusual physics such as the X-factor.   Refs: [1] X. Zeng, et al., Phys. Rev. A 31, 260 (1985); [2] W.C. Chen, et al., J. Appl. Phys. 116, 014903 (2014).

Funding acknowledgement

Suppported by NSF PHY-2110608

POSTERS (141)