  Radical-ion-pair reactions were recently shown to represent a rich
biophysical laboratory for the application of quantum measurement theory
methods and concepts, casting doubt on the validity of the theoretical
treatment of these reactions and the results thereof that has been at the core
of spin chemistry for several decades now. The ensued scientific debate,
although exciting, is plagued with several misconceptions. We will here provide
a comprehensive treatment of the quantum dynamics of radical-ion-pair
reactions, generalizing our recent work and elaborating on the analogy with the
double-slit experiment having partial "which-path" information. This analogy
directly leads to the general treatment of radical-ion pair reactions covering
the whole range between the two extremes, that of perfect singlet-triplet
coherence and that of complete incoherence.
