Magnetic field effect determination

In some systems, triplet BET can occur, as deduced from time-resolved optical spectroscopy, magnetic field effects, CIDNP, or optoacoustic calorimetry. Triplet BET is governed by energetic factors, which determine rates, and by the relative topologies of the potential surfaces of parent molecule, radical ions, and of accessible triplet or biradical states. Divergent topologies for different states may cause rearrangements. 

To summarize Section 18d, we can determine our four basic electrical parameters, n, p, p , and pp, in the presence of both single- and mixed-carrier magnetic field effects, from any four of the following equations ... 

The electron Zeeman effect arises from the interaction of unpaired electrons with the external magnetic field and determines the position at which resonance occurs [i.e., the deviation of the g-factor from the free electron value (g = 2.00232)]. Species with axial symmetry, such as Cu2+ and V " " (i.e., with one principal axis of symmetry, conventionally the z-axis, and equivalent x> and y-axes), exhibit two g-values, usually labeled gy = i.e., the g-value along... 

There are several approaches [4, 25] that try to determine the fraction of spin-correlated radical ion pairs in radiolysis. The transient emission and absorption [25] suffer, however, from the lack of exact data on the extinction coefficients and luminescence quantum yields of intermediate products. The magnetic field effect technique [4] is more straightforward. However, it requires a detailed knowledge of spin evolution in zero field which is a problem in most cases. 

Superficially, these estimates correlate well with the energy dependence of the singlet ratio determined from the magnetic field effects on the solute... 

The mechanism of Zeeman relaxation in collisions of molecules in electronic states with nonzero electronic orbital angular momenta is different from that in collisions of E-state molecules. The response of non-E-state molecules to a magnetic field is determined by both the electron spin and the orbital angular momentum of the electrons in the open electronic shell. The orbital motion of the electrons induces electronic anisotropy, which gives rise to multiple adiabatic interaction potentials between the collision partners [20]. Consider, for example, the collision system of a hydrogen atom in an excited P state and a structureless atom, such as He. The interaction between the atoms can be described by an effective potential as a function of the interatomic distance and an angle between the direction of the electronic F-orbital and the interatomic separation line. The angular dependence of this potential is the electronic anisotropy. An alternative description of the interatomic interaction can be... 

What is the difference between equations 16.14 and 16.11 In equation 16.14, we are considering the effect on one electron, whereas equation 16.11 is a more general case with more than one electron. For a single electron, the magnetic field effects are determined by m, whereas for multiple electrons the effects are better described by 7 and M . Therefore, for multiple electrons gj and Mj are the appropriate variables, and for a single electron g, and are the relevant variables. 

Although the resonance frequency of a nucleus in a magnetic field is determined principally by y, it also depends, slightly, on the immediate surroundings of the nucleus. This effect, the chemical shifty is of crucial importance for chemical applications of NMR because it allows one to distinguish nuclei in different environments. For example, the H spectrum of liquid ethanol (Figure 2) shows clearly that there are three types of protons (methyl, methylene and hydroxyl). 

In the above reaction scheme Solv" ", C-RH+, S represent the solvent cation, cyclohexane cation and hexafluorobenzene (HFB) anion respectively. The spin-dynamics of S and c-RH+ determine the magnetic field effect, since the spin wave-function for the ion pair (S / c-RH+) evolves differently at the different magnetic field strengths. The intensity of recombination fluorescence of the solution is determined by the rate of radiative deactivation of S [reaction (7)], which is accumulated within the simulation program. Although this model is not a complete description of the radiolysis of n-hexane which contains a solution of HFB and cyclohexane, it does however, take into account the most important aspect of the proposed relaxation mechanism, namely cross recombination. A more detailed reaction scheme for the radiolysis of n-dodecane is considered later in this chapter (in Sect. 8.6), which takes into account the excited state chemistry as well as spin-exchange reactions. 

The development of Remote Field Eddy Current probes requires experience and expensive experiments. The numerical simulation of electromagnetic fields can be used not only for a better understanding of the Remote Field effect but also for the probe lay out. Geometrical parameters of the prohe can be derived from calculation results as well as inspection parameters. An important requirement for a realistic prediction of the probe performance is the consideration of material properties of the tube for which the probe is designed. The experimental determination of magnetization curves is necessary and can be satisfactory done with a simple experimental setup. 

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