Fine interaction

Suppose we have an isolated system with a single unpaired electron and no hyper-fine interaction. Mononuclear low-spin Fe111 and many iron-sulfur clusters fall in this category (cf. Table 4.2). The only relevant interaction is the electronic Zeeman term, so the spin Hamiltonian is... 

The spin-orbit effect contributes both to the deviation of the molecular -tensor from the spin-only value, and to the metal hyper-fine interaction. We can use experimental values of the former to estimate the latter ... 

Since core polarization effects are not included in the present DSW calculations, no Fermi contribution to the metal hyper-fine interaction arises from the present wavefunction, although its contribution to the experimental tensor is significant. We have discussed such core polarization effects elsewhere.O, )... 

Oh, S.J. Cook, D.C. Townsend, H.E. (1998) Characterization of iron oxides commonly formed as corrosion products on steel. Hyper-fine Interactions 112 59-65 Ohmori, M. Matijevic, E. (1992) Preparation and properties of uniform coated inorganic colloidal particles. VII. Silica on hematite. J. Colloid Interface Sci. 150 594-598 Ohta, S. Effendi, S. Tanaka, N. Miura S. (1993) Ultisols of lowland Dipterocarp forest in East Kalimantan, Indonesia. Soil Sci. Plant Nutr. 39 1-12... 

Most structural characterization of these complexes has been carried out by EPR methods (64, 73- 76) and, with a few notable exceptions, the nickel(III) species show the expected elongated tetragonal geometry with axial coordination of solvent or counterions confirmed by hyper-fine interactions (Table I). The smallest member of the tetraaza macrocycle series, [12]aneN4, is unusual in that the ligand folds to give cis coordination because the metal ion is too large to allow a planar... 

Lubbers, R., Rupprecht, K., Wortmann, G., 2000. Hyper-fine Interactions 128, 115. 

AEq = 0.37 for the LS (1A1) state (relative to natural ion at 298 K). Debye-Waller factors were determined for the two states. The values -lnf(sT2) and -lnfi A,) follow the Debye model between 175 and 250 K with 0D (ST2) = 126 K and between 105 and 225 K with 0D (J Aj) = 150 K, respectively. Deviations encountered outside these regions were considered as evidence for the formation of cooperative domains as suggested by Sorai and Seki34,87T The difference between the Debye temperatures 0d(5T2) and 0d( Ai) may well be understood in terms of more rigidity in the lattice of the 2A state as compared to that of the ST2 state. A study of the magnetic hyper-fine interaction at 4.2K yielded VZZ( A1) < O. VZZ(5T2) > O, however, was concluded from the spin reversal of the texture-induced asymmetry of the Mossbauer line intensities. 

The unpaired electron with its spin S = 1/2 in a sample disposed into the resonator of the EPR spectrometer interacts magnetically a) with the external magnetic field H (Zeeman interaction) b) with the nuclear spin of the host atom or metal ion / (hyperfine interaction) c) with other electron spins S existing in the sample (dipole-dipole interaction). In the last case, electrons can be localized either at the same atom or ion (the so called fine interaction), for example in Ni2+, Co2+, Cr3+, high-spin Fe3+, Mn2+, etc., or others. These interac-tions are characterized energetically by the appropriate spin-Hamiltonian... 

The orientations of the monomers for a number of complexes found from hyper-fine interactions are given in Table 5 as effective angles yA for the proton acceptor and yD for the proton donor i.e. 

R505 P. C. Riedi, Cz, Kapusta, Y. Kohori and G. J. Tomka, Volume Dependence of NMR of Ordered Correlated Electron Systems , Hyper-fine Interact., 2000,128, 167... 

Oil slicks and oil on shorelines sometimes interact with mineral fines suspended in the water column and the oil is thereby transferred to the water column. Particles of mineral with oil attached may be heavier than water and sink to the bottom as sediment or the oil may detach and refloat. Oil-fines interaction does not generally play a significant role in the fate of most oil spills in their early stages, but can have an impact on the rejuvenation of an oiled shoreline over the long term. 

Similarly, the generic expression for the energy shift of a level induced via the hyper-fine interaction is given by... 

Sedimentation and oil-fines interaction Sedimentation is the process by which oil is deposited on the bottom of the sea or other water body. Once oil is on the bottom, it is usually covered by other sediments and degraded very slowly. Following the Exxon Valdez oil spiU in Prince William Sound, Alaska in March 1989, the process of oil-mineral fine aggregates was discovered as a mechanism affecting the rate of natural cleansing of oil residues from shorelines. " Oil-mineral aggregates were found to result from interactions among the oil residues, fine mineral particle, and seawater. Particles of mineral with oil attached may be heavier than water and sink to the bottom as sediment... 

Altliougli EPR is very sensitive to tlie surroundings of the paramagnetic cation, it cannot provide directly infonnation concerning the fine interactions with the framework. Such interactions can, however, be measured by ESEEM. This teclmique is particularly useful for the measurement of weak hyperfine interactions. The modulation frequencies are the NMR frequencies of the coupled nuclei. In disordered systems, the modulation frequencies are essentially the Lannor frequencies of the coupled nuclei, which serve to identify the coupled nuclei. The modulation depth can be related to the distance between the electron spin and the coupled nuclei, and to their number. The ESEEM measurements described here were carried out at 4 K using an operating frequency of 9.1 GHz. Both two-pulse and three-pulse sequences were employed. 

Elquation 5.1 4 indicates that at the 0 temperature, the morphological state of a coil is characterized by a balance of fine interaction effects concerned with the two-body attraction interactions being compensated for by the three-body repulsion interactions. 

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