NMR instabilities and spectral clustering in laser-polarized liquid xenon

Abstract

To study how highly magnetized liquids behave in NMR experiments, we have performed low-field NMR on laser-polarized liquid 129 Xe, with nuclear polarization of up to 6%. Contrary to conventional NMR results, we find that instabilities develop after a large pulse, leading to an unexpectedly abrupt decay of the signal. In contrast, the NMR spectrum after a small pulse collapses to a series of unusually sharp lines ͑spectral cluster-ing͒, whose widths correspond to precession lifetimes longer than a half minute. We discuss the key role of long-range dipolar coupling in such spin dynamics.

Optically pumped InP: Nuclear polarization from NMR frequency shifts

“…This is equivalent to assuming that γ P ∆B d τ decay ≪ 1, where ∆B d represents the variation of the demagnetizing field over the irradiated region. Further, with the use of a small flip angle, we avoid the instabilities predicted theoretically 49 , and observed experimentally 50 , with large flip angles applied to highly polarized spin systems.…”

Hyperpolarized xenon in NMR and MRI

“…Because of the very large nuclear magnetization of liquid xenon, and as a manifestation of the combined effect of long range dipolar interaction and radiation damping (Lin et al 2000), the NMR signal following strong radiofrequency pulses presents an unexpected chaotic behaviour, resulting in an abrupt decay of the transverse magnetization (Jeener 1999, Nacher et al 2000, Sauer et al 2001. Suppression of these instabilities led Romalis and Ledbetter (2001) to a particularly stable, highly magnetized system.…”

“…An alternative solution, which benefits from both increased density over gas phase and the efficiency of Xe as a solvent (Rentzepis and Douglass 1981) is to use liquid Xe for imaging, or as a solvent, for magnetization transfer to other nuclear species. Because of the high magnetization density, combined effects of the distant dipolar field and radiation damping give rise to interesting dynamics in polarized Xe liquid (Jeener 1999, Nacher et al 2000, Sauer et al 2001, Romalis and Ledbetter 2001, Jeener 2002.…”

Controlling the dipole-dipole interaction using NMR composite rf pulses

“…In this dense liquid, 3 He nuclear spins 1/2 are polarized by optical pumping up to 20% and present a strong long range dipolar interaction 6 in comparison with solids where the dynamics is dominated by promiscuous spins. Peculiar dynamical behaviours have been observed, in particular spectral clustering at low tip angle and the instability of the uniform magnetization at large tip angle 7,8 . In this system, the MS has been successfully applied to stabilize the NMR evolution and should allow to gain insight on the development of incipient turbulent spin dynamics 5,9 .…”