Coupled spin 1/2 systems

A quantum mechanical treatment combined with the density matrix formalism extends the description to include the dynamic spectra of spin-coupled systems. (34-38) Further developments in the theory and presentation thereof, in a form suitable for computer calculations, are due to Binsch et al., and to Kaplan et al. (14, 15, 39) However, even the recent theories are not rigorous in certain aspects and contain some errors. This is particularly true in the case of the intermolecular exchange of spins. 

Intense irradiation of a proton (or equivalent protons) at its resonance frequency in a spin-coupled system removes the proton s coupling effect on the neighboring protons to which it has been coupled. Thus successive irradiation of the protons of 1-propanol, for example, yields the following results ... 

A. X. Trautwein, E. BiU, E. L. Bominaar and H. Winkler, Struct. Bonding, 1991, 78, 1. A thorough overview on spin-Hamiltonian parameters and Mossbauer spectroscopy with a lot of examples of spin-coupled systems. 

Now let us examine the most fundamental 2D experiment, COSY, in terms of the product-operator formalism. Most of the relationships developed in the earlier equations will be utilized. The pulse sequence (Figure A6-1) involves two pulses separated by a period fj and followed by a second period t2 - 90°-fi 90°-t2(acquire). The effects of chemical shifts and coupling constants are expressed during both periods. The theory may be understood by examining a two-spin coupled system (nuclei i and j). The expression... 

For spin-coupled systems the EPR spectrum may be temperature dependent due to temperature-dependent populations of excited states. For example, in strongly antiferromagnetically coupled copper(II) dimers, there is no EPR signal at low temperatures, but a characteristic triplet (5 = 1) signal grows in as the temperature is increased due to thermal population of the excited state. ... 

SPIN-COUPLED SYSTEMS METAL-RADICAL SYSTEMS AND SPIN-COUPLED DINUCLEAR COMPLEXES 497... 

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