The magnetic moment of103Ru

The nuclear magnetic moment of¹⁰³Ru has been determined using the technique of low-temperature nuclear orientation on¹⁰³Ru as a dilute impurity in Fe. The Fe lattice was cooled to 1.7 mK using a PrNi₅ enhanced nuclear demagnetisation stage precooled with a³He–⁴He dilution refrigerator. The¹⁰³RuFe system was observed to have a long nuclear spin-lattice relaxation time, but analysis of the relaxation indicates that the¹⁰³Ru nuclei are close to thermal equilibrium with the Fe lattice at times>200 min after demagnetising. From the near thermal equilibrium anisotropy of the 497 keV -ray in¹⁰³Rh we have deduced the nuclear magnetic moment as |(¹⁰³Ru)|=0.18(2)_N. This value is almost independent of the choice of spinI=3/2 or 5/2 for the nucleus, but is only consistent with systematics ifI(¹⁰³Ru)=3/2 and <0. UsingI=3/2 we obtain the E2/M1 mixing ratio of the 497 keV -ray as =–0.42(4). The sign of the anisotropy of the 610 keV -ray from the 650 keV level in¹⁰³Rh is only consistent with an allowed -decay to the state ifI(650 keV,¹⁰³Rh)=5/2. The E2/M1 mixing ratio of the 610 keV -ray is then =+0.15(3) or +60( _–40 ⁺ ), <–80. From the initial rise in -ray anisotropy following demagnetisation we determine the Korringa constant for¹⁰³RuFe to beC=5.7(5) K·s.     

EFFECT OF SINGLET OXYGEN QUENCHERS ON OXIDATIVE DAMAGE TO LIPOSOMES INITIATED BY PHOTOSENSITIZATION OR BY RADIOFREQUENCY DISCHARGE

Abstract —Lipid model membrane systems, liposomes, may be oxidized by both toluidine blue Osensitized photo-oxidation and radiofrequency-discharge-generated singiet oxygen. Oxidation can be followed by the appearance of lipid peroxides, malondialdehyde formation, and ultimately by the lysis of the liposomes. Inhibition of oxidation is observed in both systems using either β-carotene or DABCO. These observations are consistent with the view that type II (singlet oxygen) reactions are involved in this photodynamic system.     

Neutron captue prompt gamma-ray activation analysis at the NIST Cold Neutron Research Facility

An instrument for neutron capture prompt gamma-ray activation analysis (PGAA) has been constructed as part of the Cold Neutron Research Facility at the 20 MW National Institute of Standards and Technology Research Reactor. The neutron fluence rate (thermal equivalent) is 1.5·10⁸ n ·cm^–2·s^–1, with negligible fast neutrons and gamma-rays. With compact geometry and hydrogen-free construction, the sensitivity is sevenfold better than an existing thermal instrument. Hydrogen background is thirtyfold lower.     

Structural similarities and differences among mixed-metal clusters containing a single M(PPh3) (M = Cu, Ag or Au) fragment

The heteronuclear metal clusters [H₃MRu₄(CO)₁₂(PPh₃)] and [MFe₃(μ-COMe)(CO)₁₀(PPh₃)] (M = Cu, Ag or Au) have been prepared; the gold-tetraruthenium cluster has a different metal core geometry to that adopted by the copper and silver analogues, whereas all three iron-Group IB mixed-metal clusters have the same geometry.     

Multiple state emission from rhodium(I) and iridium(I) complexes

The effect of temperature (2–100 K) on the emission spectra and lifetimes of [M(2 = phos)₂]ClO₄ (M = Rh(I), Ir(I): 2 = phos is cis-1,2-bis-(diphenylphosphino)ethylene) is interpreted with a two-level spin-orbit-split emitting manifold. For [Ir(2 = phos)₂]ClO₄, Δ? = 143cm^?1, τ(lower) = 999μs, and τ(higher) = 1.54 μs. For the rhodium species, Δ? = 35 cm^?1, τ(lower) = 5920 μs, and τ(higher) = 20.3 μs.