Overview of some quantum effects in chemistry

This article is a brief tutorial dealing with the conceptual aspects of (i) excitation transfer in molecular assemblies, such as occurs in the early steps of photosynthesis, (ii) radiationless transitions, which are ubiquitous participants in the light induced isomerization reactions that support vision and (iii) active control of product selection in a chemical reaction. All of these processes exhibit explicit quantum effects that arise from competition between coherent and incoherent evolution of the initial state of the system expressed in the atom and/or electron dynamics. Topic (iii) is associated with how a molecular assembly can be designed to optimize the use of coherent processes to improve efficiency of conversion of the initial excitation to product under the constraint that there are fluctuations in the surrounding medium.