Robust solidXe129longitudinal relaxation times

Abstract

We find that if solid xenon is formed from liquid xenon, denoted "ice", there is a 10% increase of 129 Xe longitudinal relaxation T1 time (taken at 77 K and 2 Tesla) over a trickle-freeze formation, denoted "snow". Forming xenon ice also gives unprecedented reproducibility of 129 Xe T1 measurements across a range of 77-150 K. This temperature dependence roughly follows the theory of spin-rotation mediated by Raman scattering of harmonic phonons (SRRS), though it results in a smaller-than-predicted spin-rotation coupling strength cK0/h. Enriched ice 129 Xe T1 experiments show no isotopic dependence in bulk relaxation mechanisms at 77 K and at kilogauss fields.

Thermal annihilation of photo-induced radicals following dynamic nuclear polarization to produce transportable frozen hyperpolarized 13C-substrates

“… 17 would allow transporting the solid sample to a remote location prior to melting. It is noteworthy that it has also been demonstrated that hyperpolarized 129 Xe can be stored for an extended period of time and transported in the solid form at cryogenic temperature 28 29 .…”

Spin Hyperpolarization in Modern Magnetic Resonance

“…One focus of this review is on the measures that have been taken to circumvent the challenges presented by the transient nature of spin hyperpolarization. Examples include generating hyperpolarization in situ (i.e., at the point of detection) to avoid relaxation losses during transport, , choosing/changing the state of matter to take advantage of slower relaxation, for example, in cryogenically cooled solids, , transferring the hyperpolarization to slower-relaxing lower-γ nuclei with the possibility to transfer back to a high-γ nucleus for a more sensitive readout, , and temporarily storing hyperpolarization in long-lived spin states. ,− …”

A semi-empirical model to optimize continuous-flow hyperpolarized 129Xe production under practical cryogenic-accumulation conditions

“…The improved accumulation rates and absolute polarization achieved with the richer 129 Xe blend highlight the importance of solid-state T 1 relaxation in the 129 Xe snow as demonstrated in Figure 5, where 1000 mL accumulations were simulated for 129 Xe blends of f = 1%, 2% and 3% as a function of accumulation time. Here, two T 1 snow times are considered: 150 minutes, reported by M. E. Limes et al [21] for 129 Xe in 77 K polycrystalline snow, and the shorter 84 minutes in 129 Xe snow extracted from the experimental data in this work. Unsurprisingly, deviations in the behavior predicted for the two relaxation times are minimal for all three gas blends at low accumulation times (20 minutes or less).…”

“…One major motivation for cryogenic accumulation stemmed from Driehuys, et al [20], where the T 1 relaxation time in crystalline 'ice' 129 Xe was thought to be very long (180 minutes) at liquid N 2 temp (77 K) [52,53]. However, M. E. Limes et al [21] showed that the T 1 relaxation time in polycrystalline 'snow' at 2.0 T is 30 minutes shorter than in crystalline ice, suggesting that losses during cryogenic accumulation may be non-trivial. Norquay, et al…”

“…While some buffer gases can be separated directly from gaseous HP 129 Xe-e.g., isobutene by condensation [18] or H 2 by combustion [19]-the most commonly used buffer gases (N 2 and He) are removed by freezing out within a cryogenic trap submerged in liquid nitrogen [20]. HP 129 Xe is then deposited as polycrystalline 'snow', and the polarization is preserved, because the T 1 relaxation times of solid 129 Xe (150 minutes in snow-phase 129 Xe at 77 K in 2.08 T [21]) are longer than typical HP 129 Xe accumulation times of < 60 minutes. Gas flow rates and accumulation times are adjusted to cryogenically collect the desired volume of HP 129 Xe, and the xenon snow is sublimated to dispense the concentrated HP 129 Xe gas.…”