Dipole rotator

Alternately, a benign shock compression model has been invoked to explain the polarizations. An elastic dipole-rotation model was first proposed... 

The principle of FMW involves the heating of both the solvent and the matrix by wave/matter interactions. The microwave energy is converted into heat by two mechanisms dipole rotation and ionic conductance. The heating is, therefore, selective with only polar or moderately polar compounds susceptible. Due to the use of low microwave energy the structure of target molecules remains intact. 

There is greatly renewed interest in electron solvation, due to improved laser technology. However it is apparent that a simple theoretical description such as implied by Eq. (9.15) would be inadequate. That equation assumes a continuum dielectric with a unique relaxation mechanism, such as molecular dipole rotation. There is evidence that structural effects are important, and there could be different mechanisms of relaxation operating simultaneously (Bagchi, 1989). Despite a great deal of theoretical work, there is as yet no good understanding of the evolution of free-ion yield in polar media. 

Differences in sample size, shape and composition can also affect heating rates. The last case particularly applies when ionic conduction becomes possible through the addition or formation of salts. For compounds of low molecular weight, the dielectric loss contributed by dipole rotation decreases with rising temperature, but that due to ionic conduction increases. Therefore as an ionic sample is microwave-irradiated, the heating results predominantly from dielectric loss by dipole rotation initially, but the contribution from ionic conduction becomes more significant with temperature rise. 

An exception is the intercollisional dip which may be striking, especially in lines generated by isotropic overlap-induced dipoles rotational lines are less affected. 

Fuoss, R. M. Electrical properties of solids. VI. Dipole rotation in high polymers. J. Am. Chem. Soc. 63, 369—378 (1941). Note The dielectric data of Fig. 15 were taken from Document No. 1460, Amer. Documentation Inst. Library of Congress, Washington, D. C. 

Due to the particular effects of the microwaves on matter (namely dipole rotation and ionic conductance), heating of the section, including its core, occurs instantaneously, resulting in rapid breakdown of protein crosslinkages. Furthermore, the extraction and recovery of a solute from a solid matrix with microwave heating is routinely obtained in the field of analytical chemistry (Camel, 2001). However, a definite, full explanation of the effects of microwave heating on the molecular aspect of antigen retrieval is awaited. 

The trajectories of the major portion part of dipoles-rotators occupy in this case almost all the sphere (it is seen in Figs. 7 and 9). Consequently, a nonhomogeneity of the potential (94) could be neglected also in this case. Thus again we may consider free rotation of a dipole, but now in a zero potential, unlike the small-(3 case considered above. Hence, the kinetic energy of a dipole... 

Inside a rectangular well a dipole rotates freely until it suffers instantaneous collision with a wall of the well and then is reflected, while in the field models a continuously acting static force tends to decrease the deflection of a dipole from the symmetry axis of the potential. Therefore, if a dipole has a sufficiently low energy, it would start backward motion at such a point inside the well, where its kinetic energy vanishes. Irrespective of the nature of forces governing the motion of a dipole in a liquid, we may formally regard the parabolic, cosine, or cosine squared potential wells as the simplest potential profiles useful for our studies. The linear dielectric response was found for this model, for example, in VIG (p. 359) and GT (p. 249). 

Fluctuating moments thus produce a relaxation proportional to their mean square value at a faster rate than that of permanent dipole rotations because of the added effect of the rotations in relaxing the 6p correlations. Although it seems to be gener-... 

Our final discussion in this chapter concerns a very recent and remarkable observation of an electric dipole rotational transition in the Hi molecular ion [257]. Since this... 

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