Entropy Considerations in Spin-Selective Radical-Ion-Pair Reactions

TL;DR

This paper compares different theoretical models of spin-selective radical-ion-pair reactions using entropy as a fundamental measure to evaluate their physical plausibility and consistency.

Contribution

It introduces an entropy-based framework to assess and compare competing quantum theories of radical-ion-pair reactions, highlighting the importance of fundamental physical principles.

Findings

Entropy constrains the validity of quantum reaction models

The traditional and alternative theories differ in their entropy predictions

Entropy considerations can identify physically plausible models

Abstract

Radical-ion-pair reactions were recently shown to manifest a host of non-trivial quantum effects accounted for by quantum measurement theory. An alternative approach purporting to describe the fundamental quantum dynamics of spin-selective radical-ion pair reactions was introduced most recently, bringing to three the competing theories, including the one traditionally used in spin chemistry. We here consider entropy as a fundamental concept enabling a comparison of the predictions of these theories against what is physically acceptable on quite general grounds.