Nuclear Magnetic Resonance ofXe129in Natural Xenon

Abstract

Nuclear magnetic resonance studies of natural xenon have been continued using fluid samples with improved purity. The Xe 129 spin-lattice relaxation time in the gas was found to be inversely proportional to the density: 1/7*1 = (5.0db0.5)X10 -6 p, where 7i is in sec and p in amagats. For the liquid in equilibrium with its vapor, the relaxation time throughout the temperature range 0° to -72°C is 1000±200 sec. In both the gas and the liquid the paramagnetic shift in the resonant value of the local field H at the nucleus, relative to its value for the isolated atom in the same external field, is directly proportional to the density and the external field: AH = + (4.22=L0.05)X10~7 pH 0 , where AH and H 0 are in G and p is in amagats. The above T\ and AH data agree well with a relationship derived by Torrey involving an analysis of the fluctuating magnetic field at a nucleus due to the rotation of a diatomic configuration. The derivation is based on Ramsey's theory of the chemical shift and the spin-rotational coupling which exist when two atoms are sufficiently close to interact. * Based on a

Hyperpolarized xenon in NMR and MRI

“…The main relaxation mechanism at high densities was confirmed to be spinrotation, as identified by the older studies (Streever andCarr 1961, Hunt andCarr 1963). For lower pressures, which can only be efficiently investigated using hyperpolarized xenon, they suggested that wall effects become dominant below 3 amagat.…”

“…The influence of pressure and temperature on the chemical shift in gas, liquid and solid, as well as the underlying mechanisms have been studied. Streever and Carr (1961) and then Hunt and Carr (1963) studied the range of chemical shifts and longitudinal relaxation rates in gaseous and liquid xenon. Their observations showed that the chemical shift is accurately proportional to density over a range extending from rarefied gases well into the liquid phase, and determined the proportionality constant to be 0.422 ppm (the density being expressed in amagat).…”

“…Detailed information about the relaxation behaviour of xenon was gained from the studies of (Streever and Carr 1961), followed by Brinkmann et al (1962) and Hunt and Carr (1963). Streever and Carr determine the density dependence of the relaxation time in gas as T 1 ∼ ρ −2.1±0.4 for pressures between 48 and 73 atm, with the maximum measured T 1 of 2600 ± 600 s at 48 atm.…”

Novel nuclear magnetic resonance techniques for studying biological molecules

“…This enhancement factor represents a loss of almost two orders of magnitude compared to the 129Xe polarization typically prepared by the optical pumping apparatus. It is likely that paramagnetic impurities in the metal valves and tubing were responsible for this loss in polarizatio~, because the T 1 relaxation times of xenon in the solid, liquid, and gas phases are extremely long, and no significant loss of polarization is suffered during transitions between phases [58,144,162,163]. Furthermore, once the supercritical state was achieved, the 129Xe polarization was observed to last for hundreds of seconds.…”

Robust solidXe129longitudinal relaxation times

“…The corresponding Hamiltonian is given by c K (r)K · N, with coupling strength c K (r) between a nuclear spin K and the rotational angular momentum N of a pair of xenon atoms separated by a distance r [17]. In the gas and liquid phases, the rotational angular momentum N of the pair is provided by a colliding pair of Xe atoms-transient and/or persistent (van der Waals) dimers [6,[18][19][20]. In the solid phase, the orbital angular momentum of a neighboring Xe pair comes from the phonon bath, which can be analyzed to determine the ex- * mlimes@princeton.edu Xe T1 data from this work shown plotted vs. temperature for both naturally abundant ice and snow, as well as comparable data from Refs.…”