Eur. Phys. J. Plus (2014) 129: 187
https://doi.org/10.1140/epjp/i2014-14187-x

Regular Article

Lamb shift in radical-ion pairs produces a singlet-triplet energy splitting in photosynthetic reaction centers

Department of Physics, University of Crete, 71103, Heraklion, Greece

^* e-mail: ikominis@physics.uoc.gr

Received: 22 March 2014
Accepted: 23 July 2014
Published online: 3 September 2014

Abstract

Radical-ion pairs, fundamental for understanding photosynthesis and the avian magnetic compass, were recently shown to be biological open quantum systems. We here show that the coupling of the radical-pair spin degrees of freedom to its decohering vibrational reservoir leads to a shift of the radical-pair magnetic energy levels. The Lamb shift Hamiltonian is diagonal in the singlet-triplet basis, and results in a singlet-triplet energy splitting physically indistinguishable from an exchange interaction. This could have significant implications for understanding the energy level structure and the dynamics of photosynthetic reaction centers.