Magnetic field assisted separators

Figure 1.56 Representations of magnetic field assisted separators, (a), (b) low intensity (c) high intensity (d) high gradient. Photographs with permission from Eriez.

The inhomogeneity of the micellar aggregate also affords assisted spin trapping and the exploitation of magnetic field effects on the charge separated ion pairs [48]. Optical modulation spectroscopy can be used, for example, to follow the decay of radicals formed in homogeneous solution and in SDS micelles. Enhancements of a factor of about 50 in the lifetimes and the steady state concentrations of the radical were observed in the micelle, and a kinetic analysis led to a value of 2 x 103 s 1 for the exit rate constant from the micelle [49]. 

As the preceding examples demonstrate, magnetic field effects can be useful in identifying the nature of charge-transfer intermediates in photoelectron transfer. In particular, with a better understanding of the relationships between AEhf and J, and between J and the separation distance, we can predict that magnetic-field experiments, similar to those pioneered by Weller, will assist in differentiating exciplexes and CIP s from SSIP s. 

Conventional filtration methods for separation generally use physioal devices such as membranes, sieves or filtration beds and force-driven methods suoh as settling, flotation or centrifugation. Some invoive the assistance of external (eleotrio or magnetic) fields. 

Figure 6 shows the effect of these avoided level crossings can be seen in hysteresis loop measurements. When the applied field is near an avoided level crossing, the magnetization relaxes faster, yielding steps separated by plateaus. As the temperature is lowered, there is a decrease in the transition rate due to reduced thermal-assisted tunneling. 

In 1907, J. J. Thomson observed that when a vacuum tube is filled with neon gas under low pressure, the introduction of magnetic and electric fields produces two parabolic luminescent paths of canal rays (see chapter 1), corresponding to two different masses (20 and 22) for charged particles. The potentially revolutionary results were treated cautiously since impurities could be the cause. In 1909, Francis William Aston (1877-1945) became Thomson s assistant at Cambridge. Aston and Thomson attempted to apply Graham s law of diffusion to separate the two different components of neon gas and, after thousands of cycles of diffusion operations, obtained in 1913 a mass difference of 0.7 between the hghter and heavier fractions. World War I delayed continuation of this groundbreaking project for a few years. 

For measuring heteronuclear dipolar couplings in oriented systems, a new separated local field experiment has been presented. The method is based on the dipolar assisted polarization transfer (DAPT) pulse sequence proposed recently for transfer of polarization between two spins I and DAPT utilizes the evolution of magnetization of the I and S spins under two... 

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