Proton spin–lattice relaxation rate in supercooled H2O and H2 17O under high pressure

Abstract

The proton spin-lattice relaxation rate has been investigated as a function of pressure (p<250 MPa), temperature (180 K<T<300 K), and oxygen-17 enrichment (25.7 atom-%, 50.7 atom-%) in metastable water. Intramolecular proton-oxygen 17 dipolar interactions in light water in relation to deuterium electric quadrupole interactions in heavy water carry similar dynamic information and allow the complicated dynamic isotope effect in liquid water to be investigated in the whole metastable range. Under hydrostatic pressure the proton relaxation rate curve R 1 (T, p, wH) has been investigated at five different Larmor frequencies (100 MHz<w<500 MHz). These experiments unequivocally prove the isotropy of reorientational motions of water molecules on a nanosecond time scale and demonstrate the necessity to include fast quasilattice vibrations into a consistent interpretation of the relaxation rates in the dispersion regime.

Nuclear Magnetic Resonance characterization of traditional homeopathically manufactured copper ( Cuprum metallicum ) and plant ( Gelsemium sempervirens ) medicines and controls

“…Box 12: If we consider the relaxation between two non-identical spins I and S, the above equations should be modified in the following way 47,48 : It follows therefore that rotational relaxation via 17 O nuclear spin is not a confounding process.…”

High-pressure nuclear magnetic resonance probe designed for a narrow bore magnet system

“…In the second technique, usually referred to as high-pressure probe technique, a nonmagnetic autoclave of high mechanical strength (usually made of a beryllium-copper or titanium alloy) and the rf circuit required for the irradiation of the resonance frequency, are placed together in a wide bore magnet ͑ =72 mm͒ instead of a standard probe. Many different highpressure probe designs have been published, optimized, i.e., for high 12,39,40 or low temperature, 41-45 very high pressures 38,39,41,46,61 up to 15 kbar, 42 effective gas-solution mixing, 24,47,48 high spectral resolution, 49-53 high magnetic fields, 1,48,[54][55][56] or fast and easy handling. 1 A design, where the rf circuit also has to be built as in the probe technique but does not involve a metallic autoclave, is described by Castro and Delsuc.…”

“…[24][25][26][27][28][29] Nowadays mainly two different high-pressure NMR techniques are employed. 30 The first technique is referred to as the high-pressure cell technique and uses thick-walled glass, [31][32][33] Vespel, 29 or sapphire [34][35][36] tubes, or alternatively quartz capillaries, 37,38 which are placed in a commercial NMR probe in a similar way as an ordinary sample tube. The advantage of this technique is that the sophisticated properties (viz., short pulse length and a good B 1 profile of the radio frequency coils) of commercial probes can be used.…”

Density dependence of rotational and translational molecular dynamics in liquids studied by high pressure NMR

“…91. Within an isotropic diffusion model both sets of data could be described consistently using eqns (130, 131,45 and 48), as discussed at length by Lang et al (479) From the maxima of the relaxation rate curves, librationally averaged distances (Roll)= 0.106 nm and (RHH) =0.159 nm were obtained. Approximating the motional averaging factor F (eqn 59) by:…”

“…A solution to this problem was proposed by Lang and Liidemann (474' 4~6. 47~) and fully developed by Lankhorst et al (492) Lang et al (479) applied this approach in a HP-NMR study of undercooled light water to interpret proton relaxation rates in H20 and Hz t TO investigated as a function of pressure (p ~< 250 MPa), temperature (180 K~< T~<300 K) and Larmor frequency (100 MHz~<c%~<500 MHz). Oxygen-17 enrichment in light water provides an additional relaxation pathway to the proton spin system.…”