Spin Dynamics in Radical Pairs

This book sheds new light on the dynamical behaviour of electron spins in molecules containing two unpaired electrons (i.e. a radical pair). The quantum dynamics of these spins are made complicated by the interaction between the electrons and the many nuclear spins of the molecule; they are intractable using analytical techniques, and a naïve numerical diagonalization is not remotely possible using current computational resources. Hence, this book presents a new method for obtaining the exact quantum-mechanical dynamics of radical pairs with a modest number of nuclear spins. Readers will learn how a calculation that would take 13 years using conventional wavepacket propagation can now be done in 1 day, and will also discover a new semiclassical method for approximating the dynamics in the presence of many nuclear spins.

The new methods covered in this book are shown to provide significant insights into three topical and diverse areas: charge recombination in molecular wires (which can be used in artificially mimicking photosynthesis), magnetoelectroluminescence in organic light-emitting diodes, and avian magnetoreception (how birds sense the Earth’s magnetic field in order to navigate). 

Introduction.- Quantum Mechanics.- Semiclassical Approximations.- Molecular Wires.- Avian Magnetoreception.- Magnetoelectroluminescense.- Conclusions and Further Work.

Alan Lewis graduated in 2013 with a first class honours degree in Chemistry from the University of Oxford. While studying he began his research career investigating molecular dynamics. He also completed his D.Phil. at the University of Oxford, where, supervised by Prof. David Manolopoulos, he studied both quantum and semiclassical theories of spin dynamics and their applications to radical pairs. In 2017, Alan moved to the University of Chicago to pursue research in electronic structure theory.