Paramagnetic techniques

Of the paramagnetic techniques listed above, magnetic circular dichroism (MCD) is one of the few techniques that can identify electronic structure specific to the dithiolene chelate bound to Mo/W (111, 112). Since at this point only a handful of studies have been accomplished, the salient points of each will be summarized. 

Here Ti is the spin-lattice relaxation time due to the paramagnetic ion d is the ion-nucleus distance Z) is a constant related to the magnetic moments, i is the Larmor frequency of the observed nucleus and sis the Larmor frequency of the paramagnetic elechon and s its spin relaxation time. Paramagnetic relaxation techniques have been employed in investigations of the hydrocarbon chain... 

We have used the paramagnetic relaxation technique to study the binding locations of 5.1c, S.lf, S.lg... 

Other O2 Measurement Techniques The oxygen concentration in the emission gases of combustion processes is often measured based on the strong paramagnetic character of oxygen. A sampling line with appropriate sample treatments is required with this method. 

Electron spin resonance (or electron paramagnetic resonance) is now a well-established analytical technique, which also offers a unique probe into the details of molecular structure. The energy levels involved are very close together and reflect essentially the properties of a single electronic state split by a small perturbation. 

Optically detected magnetic resonance (ODMR) has yielded valuable information about dynamics of long-lived pholoexcitations of conjugated polymers. The technique relies upon the paramagnetic interaction of excitations with an applied magnetic field. For a particle with non-zero spin, placed in a magnetic field, the Hamiltonian is ... 

Electron spin is the basis of the experimental technique called electron paramagnetic resonance (EPR), which is used to study the structures and motions of molecules and ions that have unpaired electrons. This technique is based on detecting the energy needed to flip an electron between its two spin orientations. Like Stern and Gerlach s experiment, it works only with ions or molecules that have an unpaired electron. 

Certainly, all three of the bands observed with SF-FTIR must arise from different species, since they appear and disappear with different time courses. The peak at 1904 cm probably corresponds with that observed by ENDOR under low CO conditions, but the relationship of the other two bands to those observed under high CO is not clear, since the ENDOR technique will only detect CO molecules bound to paramagnetic species, whereas FTIR should detect all species. The SF-FTIR technique has the potential to observe the binding and reduction of a wide range of nitrogenase substrates, provided that the appropriate spectroscopic range can be accessed. This will be technically difficult, but well worth the effort. 

Giauque s technique still is used in contemporary low-temperature research. A sample containing paramagnetic ions (Fe, for example) is bathed in liquid helium under reduced pressure to chill it to a temperature below 4.2 K. The sample is held in a strong magnetic field, which aligns the magnetic... 

The spin-Hamiltonian concept, as proposed by Van Vleck [79], was introduced to EPR spectroscopy by Pryce [50, 74] and others [75, 80, 81]. H. H. Wickmann was the first to simulate paramagnetic Mossbauer spectra [82, 83], and E. Miinck and P. Debmnner published the first computer routine for magnetically split Mossbauer spectra [84] which then became the basis of other simulation packages [85]. Concise introductions to the related modem EPR techniques can be found in the book by Schweiger and Jeschke [86]. Magnetic susceptibility is covered in textbooks on molecular magnetism [87-89]. An introduction to MCD spectroscopy is provided by [90-92]. Various aspects of the analysis of applied-field Mossbauer spectra of paramagnetic systems have been covered by a number of articles and reviews in the past [93-100]. 

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