Showing papers on "Proton spin crisis published in 1970"
55 citations
TL;DR: The results of neutron activation, spectrochemical analysis and EPR measurements show that the amount of paramagnetic ions present in samples of protein solutions cannot be responsible for the decrease of T1 with respect to pure water.
52 citations
22 citations
TL;DR: In this article, the values of π-electron contributions to (H,H) coupling are calculated for a variety of unsaturated hydrocarbons using several different methods.
20 citations
20 citations
TL;DR: In this paper, the geminal coupling constant in some amino acids was found to increase with pH and this increase can account for the reported broadening of the α proton resonances of the corresponding amino acids with increasing pH.
14 citations
TL;DR: In this paper, the signs of the intermethyl proton spin-spin coupling constants in ortho, meta, and para xylene derivatives (interbenzylic coupling) have been determined by double resonance techniques.
Abstract: The signs of the intermethyl proton spin–spin coupling constants in ortho, meta, and para xylene derivatives (interbenzylic coupling) have been determined by double resonance techniques. and are positive, negative, and positive, respectively, in agreement with the predictions of theories based on σ–π interactions. The magnitudes of the coupling constants are discussed in terms of the values predicted by these theories.
11 citations
10 citations
TL;DR: In this paper, the shape of the 40 MHz proton magnetic resonance absorption line of powdered (NH4)2Ce(NO3)6 at liquid helium temperature is explained by proton spin isomerism as suggested by Tomita for solid methane.
9 citations
TL;DR: In this article, the authors studied the proton spin-lattice relaxation times of bisphenol-A polycarbonate, butyl rubber, and blends of the two polymers in the temperature range 90°-450°K.
Abstract: Proton spin-lattice relaxation times of bisphenol-A polycarbonate, butyl rubber, and blends of the two polymers were studied at 18 Mc/sec in the temperature range 90°-450°K. The proton spin-lattice relaxation is primarily dipolar in each polymer, due to methyl group reorientation and to reorientation of chain segments. In a blend of bisphenol-A polycarbonate with 7 and 10 wt of butyl, a nonexponential decay of magnetization was observed in the temperature range 280°-380°K. This was explained by the existence of two spin temperatures in these blends, indicating that processes which bring about the equilibrium within the spin system are slow compared to the spin-lattice relaxation times of the two components of the blend.
7 citations
TL;DR: In this paper, the proton spin-lattice relaxation time of solid methane has been measured during the conversion of the spin modifications at 4.2 K. Conversion is catalyzed by oxygen impurities.
TL;DR: In this paper, the authors measured the proton spin-lattice relaxation times of four UO2·xH2O hydrates-hydroxides at 23 Mc/sec in the temperature range from + 50 to − 140°C.
Abstract: Proton spin–lattice relaxation times of four UO2·xH2O hydrates–hydroxides have been measured at 23 Mc/sec in the temperature range from + 50 to − 140°C. The observed relaxation rate is explained as being due to reorienting water molecules and to Sz (U4+)I+ (H) coupling.
TL;DR: In this article, the proton spin -lattice relaxation time of aniline-d2 in deuterated benzene solution was determined as a function of concentration and temperature over the temperature interval 260-360 °K using a pulsed nuclear magnetic resonance technique.
Abstract: The proton spin – lattice relaxation time of aniline-d2 in deuterated aniline solution was determined as a function of concentration and temperature over the temperature interval 260–360 °K using a pulsed nuclear magnetic resonance technique. In addition the proton spin – lattice relaxation time of aniline-d2 in deuterated benzene solution at 20 °C was also determined. It was found that the activation energies of the intra- and inter-molecular relaxation rates were of similar magnitude, viz. 4.5 and 4.4 kcal/mole, respectively. It was also found that at 20 °C the rotational correlation time, τr, of the C6H5NH2 molecule in infinitely dilute perdeutero benzene solution was approximately half that of the partially deuterated aniline molecule, viz. 3.0 × 10−12 and 6.3 × 10−12 s, respectively, and that τr of C6H5ND2 in infinitely dilute perdeutero aniline solution is much larger than in infinitely dilute perdeutero benzene solution and is equal to 19 × 10−12 s.