54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 68, Number 7
Monday–Friday, June 5–9, 2023;
Spokane, Washington
Session F01: Poster Session I (4:00pm-6:00pm PT)
4:00 PM,
Tuesday, June 6, 2023
Room: Exhibit Hall C
Abstract: F01.00007 : Spin-Exchange Rate Coefficients for Rb-Xe and Cs-Xe Measured Using Rate Balance
Abstract
Presenter:
Chelsea V Weaver
(Washington State University)
Authors:
Chelsea V Weaver
(Washington State University)
Brian T Saam
(Washington State University)
Adnan I Nahlawi
(Washington State University)
Hyperpolarized noble gases, produced via spin-exchange optical pumping (SEOP), have many applications including precision magnetometry and lung MRI. The rate coefficient kse characterizes the collisional transfer of angular momentum from the alkali metal to the noble gas; there are three main methods [1] to measure it. The rate-balance method requires no assumptions about wall-relaxation, which for 129Xe is often non-negligible and temperature-dependent. Normally, the method requires a determination of both alkali-metal number density [A] and the polarization PA; we are pursuing a variant of this method in which we measure frequency shifts of both the alkali-metal resonance and the 129Xe NMR resonance under the same conditions. Measuring the NMR shift, which is proportional to PA[A], eliminates the need for direct measurement of PA or [A]. Using the expressions for the two frequency shifts [2] and forming their ratio, we obtain: kse-1 = (ΔfXe/ΔfA)([129Xe]τup/gs[2I + 1]), where gs is the electron g-factor, I is the alkali-metal nuclear spin, [129Xe] is the number density of 129Xe, and we have assumed that the enhancement factors [2] κAXe = κXeA = κ0. The characteristic spin-up time τup and the EPR shift ΔfA corresponding to full 129Xe polarization are measured by monitoring the alkali-metal EPR frequency via Faraday rotation. The NMR shift ΔfXe is measured by scanning a weak cw NMR excitation across the129Xe resonance at full 129Xe polarization (in both directions with respect to the applied magnetic field) and monitoring the alkali-metal EPR frequency to trace the NMR spectrum. We present preliminary measurements of kse for both Rb-Xe and Cs-Xe in vapor cells with a gas mixture at pressure on the order of 1 bar with 3% Xe, similar to the composition used in Xe flow-through polarizers. [1] B. Chann, et al., Phys. Rev. A, 66, 032703 (2002); [2] S.R. Schaefer, et al., Phys. Rev. A 39, 5618 (1989).