A quantum description of radiation damping and the free induction signal in magnetic resonance

Journal Article · Sun Jul 07 04:00:00 EDT 2013 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4811180· OSTI ID:22121603

Tropp, James ^[1]

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1. General Electric Healthcare Technologies, 47697 Westinghouse Drive, Fremont, California 94539 (United States)

We apply the methods of cavity quantum electrodynamics (CQED), to obtain a microscopic and fully quantum-mechanical picture of radiation damping in magnetic resonance, and the nascent formation of the free induction signal. Numerical solution of the Tavis-Cummings model - i.e., multiple spins 1/2 coupled to a lossless single-mode cavity - shows in fine detail the transfer of Zeeman energy, via spin coherence, to excite the cavity - represented here by a quantized LC resonator. The case of a single spin is also solved analytically. Although the motion of the Bloch vector is non-classical, we nonetheless show that the quantum mechanical Rabi nutation frequency (as enhanced by cavity coupling and stimulated emission) gives realistic estimates of macroscopic signal strength and the radiation damping constant in nuclear magnetic resonance. We also show how to introduce dissipation: cavity losses by means of a master equation, and relaxation by the phenomenological method of Bloch. The failure to obtain the full Bloch equations (unless semi-classical conditions are imposed on the cavity) is discussed in light of similar issues arising in CQED (and in earlier work in magnetic resonance as well), as are certain problems relative to quantization of the electromagnetic near-field.

• OSTI ID: 22121603
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 1 Vol. 139; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BLOCH EQUATIONS
COUPLING
DAMPING
NUCLEAR MAGNETIC RESONANCE
NUMERICAL ANALYSIS
QUANTIZATION
QUANTUM ELECTRODYNAMICS
QUANTUM MECHANICS
RELAXATION
RESONATORS
SIGNALS
SPIN
STIMULATED EMISSION
VECTORS
ZEEMAN EFFECT