Fig. 4.

Build-up of hp ¹³¹Xe spin polarization P as a function of SEOP time, t_p, at 2 × 10⁻³ T. Optical pumping was carried out for mixtures I (5% Xe, open circle), II (20% Xe, open square), and III (93% Xe, open triangle) under 40 W laser illumination in a pair of Helmholtz coils. Data were collected at 9.4 T after a stopped-flow delivery cycle of duration t_p. Inset: magnification of short-time polarization build-up for mixture III. The curves are fits of the data to Eq. (4), and the fitting parameter, A lead to the following maximum polarization P values: mixture I, 2.24 ± 0.03%: mixture II, 0.438 ± 0.007%; and mixture III 0.0256 ± 0.0005%.Values for the rate constant B are: mixture I, 0.030 ± 0.001 s⁻¹; mixture II, 0.037 ± 0.002 s⁻¹; mixture III, 0.085 ± 0.006 s⁻¹.