Some Thermodynamic and Quantum Aspects of NMR Signal Detection

by Stanislav Sykora (Extra Byte, Castano Primo, Italy), delivered at

the BFF6 2011 Workshop (Black Forest Focus on Soft Matter: Magnetic Resonance Microsystems),
organized by FRIAS, July 26-29, 2011, Saig (Freiburg), Germany.
See the program of this very good meeting.

Talk SLIDES ( PDF, 806 kB)   To cite/link this page: DOI 10.3247/SL4nmr11.002 NMR Articles and Posters
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Presentation Abstract

An electric LCR circuit which includes a coil containing magnetic moments can be analyzed using the method of virtual energies which is essentially a thermodynamic paradigm. Such an approach brings forth the primary character of the interaction term between the current and the magnetic moments. It will be shown, for example, that the so-called reciprocity theorem is a direct consequence of this interaction term. Analysis of the interaction uncovers also the limits of the classical law of Faraday induction and opens a road towards its generalization.

Furthermore, since the interaction term has a Hamiltonian form, it opens the possibility of making the current flowing in an inductive detector an integral part of a spin-system Hamiltonian. This, in turn, enables for the first time a full quantum analysis of the union of a spin-system and an inductive detector, thus overcoming the limitations implicit in handling the spin Hamiltonian in quantum mechanical way and its interaction with the detector in a completely unrelated classical manner.

The new approach to the quantum description of MR phenomena should help to resolve some of the known paradoxes of MR signal detection and find a number of practical applications, such as a better description of the so-called radiation damping (a term improperly associated with second-order spin-coil interaction effects), a better understanding of spin noise, and a better understanding of microcoil detector circuits.

Anticipating a more detailed paper, this presentation will outline the theory and thus allow, within the ideal setting of a Workshop, a peer discussion of the proposed paradigm.

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