The effect of an electric field on the relaxation of a spin- nucleus by a paramagnetic ion in fluid solution is calculated. The model relates to a spin—echo experiment, and depends on inter-ionic magnetic dipole—dipole relaxation. It is shown that under optimum conditions, using electric fields of strength ⪅ 10 MV m±1, the value of the nuclear T2 may be changed by about 50%.
We have studied, using infrared spectroscopy, the variation according to temperature of the widths of about ten fundamental vibration bands of furan and thiophene. This experimental investigation allowed us to determinate an approximation of the vibrational widths for each band. Adding to the above, the low frequency results obtained and those yielded by Raman diffusion measurements at room temperature, it has been possible to give a more accurate evaluation of the vibrational and rotational contributions to the widths of the bands. We have deduced the vector and tensor angular correlation times and their comparison has offered an opportunity to work out a model of molecular diffusion showing the motions of thiophene and furan in the liquid phase.
Ultrasonic absorption data in ethanol—ethyl chloride solutions reported by Solovyev et al. have been re-examined using a reaction scheme based on ethanol self-association monomer ⇌ dimer ⇌ trimer It is concluded that the excess absorption observed is due primarily to the monomer—dimer process which is assumed to be the faster step. The concentration of trimer formed is small below 0.2 mole fraction ethanol but increases rapidly above this point. The self-association of ethanol in this system is confirmed qualitatively by a PMR study.
This paper shows how a choice may be made on the basis of statistical theory between alternative dielectric dispersion equations hypothesised to fit sets of experimental data. It also shows how to find the best values and probable ranges of the parameters in the equations.
It is intended for non-specialists in statistics, and to this end the application of statistical inference to the problem is outlined descriptively, with detailed references to some recent textbooks, so as to enable the necessary background to be rapidly pieced together.
A computational approach appropriate to dielectric dispersion equations, and some features of programs devised to implement it for the Debye and the Cole—Cole equations are described.
The best fit parameters and confidence intervals obtained for these two equations when the procedures are applied to an extensive literature collection of data on water are tabulated and discussed.
It is found that the improvement in fit of the Cole—Cole equation over the Debye throughout the complete temperature range from 0 to 75 °C makes it a near statistical certainty that there is some spread of relaxation times in water over all this temperature range. At 20 °C, for example, the probability of the improvement in fit not being due to chance is greater than 99.5 %, while the 90 % confidence interval for h, the Cole—Cole spread parameter, is 0.008 < h < 0.018.
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