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Updated: Aug 23, 2026

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Approximate solutions of the Bloch-McConnell equations for two-site chemical exchange
Daniel Abergel1, Arthur G Palmer
1Laboratoire de Chimie, Ecole Normale Supérieure 24, rue Lhomond, 75005 Paris, France. daniel.abergel@ens.fr
Abstract:
Approximate formulas for the transverse-relaxation rate constant and resonance frequency have been derived for nuclear spins subject to two-site chemical exchange. The new results are more accurate than previous approximations when chemical exchange does not approach the fast-exchange limit or when site populations are not highly asymmetric. Results are derived from an effective average evolution operator that contains contributions from both exact eigenvalues of the Bloch-McConnell equations. These expressions are useful for interpretation of chemical exchange processes in NMR spectroscopy.
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