title: Systematic T1 improvement for hyperpolarized 129xenon.
abstract: The spin-lattice relaxation time T1 of hyperpolarized (HP)-(129)Xe was improved at typical storage conditions (i.e. low and homogeneous magnetic fields). Very long wall relaxation times T(1)(wall) of about 18 h were observed in uncoated, spherical GE180 glass cells of ∅=10 cm which were free of rubidium and not permanently sealed but attached to a standard glass stopcock. An "aging" process of the wall relaxation was identified by repeating measurements on the same cell. This effect could be easily removed by repeating the initial cleaning procedure. In this way, a constant wall relaxation was ensured. The Xe nuclear spin-relaxation rate 1/T1(Xe-Xe) due to van der Waals molecules was investigated too, by admixing three different buffer gases (N(2), SF(6) and CO(2)). Especially CO(2) exhibited an unexpected high efficiency (r) in shortening the lifetime of the Xe-Xe dimers and hence prolonging the total T1 relaxation even further. These measurements also yielded an improved accuracy for the van der Waals relaxation for pure Xe (with 85% (129)Xe) of T(1)(Xe-Xe)=(4.6±0.1)h. Repeating the measurements with HP (129)Xe in natural abundance in mixtures with SF6, a strong dependence of T(1)(Xe-Xe) and r on the isotopic enrichment was observed, uncovering a shorter T(1)(Xe-Xe) relaxation for the (129)Xe in natural composition as compared to the 85% isotopically enriched gas.
authors.affiliation: Institute of Physics, Johannes Gutenberg University, Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Maricel
authors.initials: M
authors.lastname: Repetto
authors.affiliation: Jülich Centre for Neutron Science, Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstrasse 1, 85747 Garching, Germany.
authors.forename: Earl
authors.initials: E
authors.lastname: Babcock
authors.affiliation: Institute of Physics, Johannes Gutenberg University, Staudingerweg 7, 55128 Mainz, Germany. Electronic address: bluemler@uni-mainz.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Blümler
authors.affiliation: Institute of Physics, Johannes Gutenberg University, Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Heil
authors.affiliation: Institute of Physics, Johannes Gutenberg University, Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Sergei
authors.initials: S
authors.lastname: Karpuk
authors.affiliation: Institute of Physics, Johannes Gutenberg University, Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Kathlynne
authors.initials: K
authors.lastname: Tullney
keywords: (129)Xe; Break-up rate; Buffer gases; Destruction rate; Isotope; Laser polarization; Longitudinal; Relaxation; Spin–lattice; Van der Waals; Wall