Showing papers on "Proton spin crisis published in 1973"
TL;DR: In this article, an experimental study of the proton spin-lattice relaxation time T1 has been made for H2O over the temperature interval from −16 to 145°C, and the experimental T1 behavior can be represented by the double exponential form of the rate expression used to treat the relaxation for the quadrupolar nuclei 2H and 17O in water.
Abstract: An experimental study of the proton spin‐lattice relaxation time T1 has been made for H2O over the temperature interval from −16 to 145°C. It is found that after correction for spin‐rotational interaction, the experimental T1 behavior can be represented by the double exponential form of the rate expression used to treat the relaxation for the quadrupolar nuclei 2H and 17O in water. The oxygen‐17 data are used to calculate the intramolecular contribution to the proton T1. The activation energies E1=9.4± 0.8 kcal/mole and E2=3.6± 0.1 kcal/mole for the two contributions to the intermolecular relaxation are in sufficiently good agreement with those for the intramolecular relaxation to indicate that the relaxation mechanism is the same in both cases. This mechanism involves two processes. The data indicate the process dominant at high temperature can be described as a rotational diffusion where the amplitude of angular motion increases with increasing temperature.
93 citations
TL;DR: In this article, the proton spin-lattice relaxation time was measured in a crystalline powder of NH 4 ClO 4 from room temperature to 4°K at Larmor frequencies of 22 and 56 MHz.
51 citations
TL;DR: In this article, two sharp peaks have been observed in the magnetic field dependence of the proton spin-lattice relaxation rate of 4-methyl 2,6-ditertiary butylphenol at liquidhelium temperatures.
Abstract: Two sharp peaks have been observed in the magnetic field dependence of the proton spin-lattice relaxation rate of $\ensuremath{\gamma}$-irradiated 4-methyl 2,6-ditertiarybutylphenol at liquidhelium temperatures. The peaks are attributed to resonances between the frequencies of tunneling rotation of the 4-methyl groups and the Larmor frequency of the unpaired electron spins associated with free radicals. One peak is assigned to the tunneling resonance of the methyl groups of the free radicals and the other to undamaged molecules.
36 citations
23 citations
TL;DR: T 1 ratios are found to be essentially constant for similar protons in compounds of widely differing molecular weight implying that segmental motion rather than bulk rotation is important in causing spin lattice relaxation.
21 citations
TL;DR: The exchange rate of the water protons in mouse tissues was determined for the first time in this article, and the process was studied by proton spin relaxation in the rotating frame.
19 citations
19 citations
TL;DR: Proton spin-spin relaxation times were measured as a function of temperature in the nematic phase of p.methoxybenzylidene and p.n.butylaniline using the 90°-45° echo as mentioned in this paper.
Abstract: Proton spin‐spin relaxation times ``T2'' were measured as a function of temperature in the nematic phase of p‐methoxybenzylidene‐p‐n‐butylaniline and in the nematic and smectic C phases of p‐n‐heptyloxyazobenzene using the 90°–45° echo. By comparing ``T2'' in these two liquid crystals, we infer that short range smectic order exists even 10° above the nematic‐smectic C phase transition in p‐n‐heptyloxyazobenzene. The angular dependence in ``T2'' was also determined in the smectic C phase at two different temperatures.
18 citations
TL;DR: Proton magnetic resonance measurements reveal on orientational order-disorder transition in solid ethylene at pressures above 468 bar near the melting line as mentioned in this paper, and strong indications that the rate of self-diffusion in the disordered solid is constant along the melting lines.
18 citations
TL;DR: Measurements on frog muscles in the Larmor frequency range 3 kHz to 75 MHz can be understood quantitatively by a log-gaussian distribution, which supports a close relation to protein solutions.
Abstract: The frequency dependence of the proton spin relaxation in muscle tissue shows that the mobility of the muscle water must be described by a continuous distribution of jumping times instead of the usually assumed two-phase model. Measurements on frog muscles (rana esculenta and rana pipiens, gastrocnemius) in the Larmor frequency range 3 kHz to 75 MHz can be understood quantitatively by a log-gaussian distribution, which supports a close relation to protein solutions.
15 citations
TL;DR: In this article, the (p, p'γ) correlation method was used to measure spin-flip angular distributions for the nuclear pairs 48, 50 Ti and 54, 56 Fe.
TL;DR: In this article, the effect of internal rotation and tumbling of the whole molecule in solution on the CH3 proton linewidth was analyzed for the anion of 3, 3′-dimethylbiphenyl.
Abstract: The proton relaxation has been studied in methyl substituted aromatic radical ions in solution. The linewidth parameter T2 of the protons in such radicals is governed by two intramolecular interactions, namely, the Fermi contact interaction and the anisotropic dipolar interaction. For the methyl protons the interactions are modulated in time by both internal rotation and tumbling of the whole molecule in solution. Equations have been derived to account for the effect of these motions on the CH3 proton linewidth. The resulting formulas are used to analyze the NMR proton linewidths for the anion of 3, 3′‐dimethylbiphenyl.
TL;DR: Sixty MHz NMR proton spectra of 15 2,4-substituted benzaldehydes and 12 methylbenzenes dissolved in different solvents have been accurately analyzed as mentioned in this paper.
TL;DR: In this article, it was shown that forbidden satellite transitions contribute to the lineshape of the trapped elctron EPR line in the 9 GHz spectrum, which has commonly been studied.
TL;DR: In this paper, the ππ exchange contribution at large impact parameter in high-energy elastic proton-proton scattering is evaluated from t -channel unitarity requirements, and the ISR data support the presence of such a contribution.
TL;DR: The frequency dependence of the proton spin dipolar relaxation time was measured in the range 24-32 MHz at 123, 127, and 131 °C in the nematic phase of the liquid crystal para-azoxyanisole as mentioned in this paper.
Abstract: The frequency dependence of the proton spin dipolar relaxation time was measured in the range 24–32 MHz at 123, 127, and 131 °C in the nematic phase of the liquid crystal para‐azoxyanisole. The experiment shows that in this liquid crystal a relaxation mechanism, too slow to relax the Zeeman energy, contributes to the relaxation of the dipolar energy. The experiment also shows that this relaxation rate does not depend on temperature or frequency within the range studied.
TL;DR: In this paper, the contribution of the intermolecular dipolar interactions has been separated by using Torrey's formula along with experimentally measured values of D. It has been found that the contributions from the proton- chlorine scalar coupling interaction and from the modulation of the intramolecular Dipolar interactions by the rotamer exchange are negligible.
TL;DR: In this article, the nuclear relaxation of a proton in an antiferromagnet CoCl 2 2H 2 O (T N = 17.2 K) was studied by using a simple phenomenological model for the spin fluctuation in onedimensional Ising spin system.
Abstract: The nuclear relaxation of proton has been studied in an antiferromagnet CoCl 2 2H 2 O ( T N =17.2 K) which is characterized by ferromagnetic linear chain of Ising-like spin S =1/2. With the external magnetic field applied along the spin axis, the field and temperature dependences of the nuclear relaxation time ( T 1 ) were measured in the three metamagnetic (antiferro-, ferri- and ferro-magnetic) states. The experimental analysis was made by using a simple phenomenological model for the spin fluctuation in onedimensional Ising spin system. It was found that the proton nuclear relaxation in CoCl 2 2H 2 O is closely related to the Ising spin excitation in its ferromagnetic linear chains.
TL;DR: The deuteron and proton spin-lattice relaxation rates of pyridine in a number of solvents were determined at 25°C using pulsed NMR techniques.
TL;DR: In this paper, the quark parton model predictions for muon pair production processes are reexamined in the light of recent experimental data of the proton and neutron structure functions.
TL;DR: In this article, the authors measured the relaxation time of the proton spin dipolar energy, T1D in hexagonal ice was measured to be 35 μsec at −24°C.
Abstract: The relaxation time of the proton spin dipolar energy, T1D in hexagonal ice was measured to be 35 μsec at −24°C. Within the accuracy of the experiment (±9%), no anisotrpy was observed when the crystal was rotated around the b axis. Measurements of the spin‐lattice relaxation time in the rotating frame T1ρ are reported for different rf fields, H1 at −2.4 and −24°C. At the lower temperature, at H1 of 7 G, T1ρ was anisotropic ([inverted lazy s] 24%) if the crystal was rotated around the b axis. This anisotropy is primarily a result of the anisotropy of the proton dipolar specific heat. The Slichter‐Ailion parameter p was calculated for rotational jumps accompanying the ultra slow diffusion of the water molecule. If two protons only are considered (one water molecule), the parameter p is isotropic and equals −0.2. The calculation was made also for the two water protons and two first neighbors. The isotropic average of this p is −0.05 if rotational jumps around two axes are excluded. If the ice lattice is simu...
TL;DR: In this article, it was shown that the rise in multiplicity with increasing perpendicular momentum transferred to the leading proton seen in recent experiments can be explained as due to double quark-quark scattering in the Glauber quark multiple-scattering model.
Abstract: It is shown that the rise in multiplicity with increasing perpendicular momentum transferred to the leading proton seen in recent experiments can be simply explained as due to double quark-quark scattering in the Glauber quark multiple-scattering model. The quark-quark inelastic-scattering amplitude is entirely consistent with the quark-quark elastic amplitudes obtained previously for elastic proton-proton scattering.
TL;DR: In this article, the procedure for treating molecular interaction is simplified by using the intermolecular orthogonalized orbital given by the method of Lowdin, and the accuracy of the approximation is examined, giving examples of the proton spin density of the solvated electron and the delocalization energy between chemically-interacting molecules.
Abstract: The procedure for treating the molecular interaction is simplified by using the intermolecular orthogonalized orbital given by the method of Lowdin, and the accuracy of the approximation is examined, giving examples of the proton spin density of the solvated electron and the delocalization energy between chemically-interacting molecules. The following is then concluded: the intermolecular orthogonalized orbital is a kind of perturbed wavefunction of the molecule interacting with the other system and can most reasonably be applied when the Mulliken-type approximation for the intermolecular integrals can well be used. Its utility with regard to the three-system problem is also briefly discussed.
TL;DR: In this paper, the authors measured proton spin-lattice relaxation times and differentiated the syn- and anti-isomers of substituted cyclobutanes, in accordance with calculated relative values.
Abstract: Measurement of proton spin–lattice relaxation times has differentiated the syn- and anti-isomers of substituted cyclobutanes, in accordance with calculated relative values.