Excitons and their equilibration
A very selective survey of exciton research is presented, with a focus on certain processes of relaxation, dephasing, and equilibration that occur during the exciton lifetime. One of these is Forster transfer, which can be viewed as either dephasing or equilibration. An old theorem of Kennard and Stepanov is discussed in a new context and proposed as a possible diagnostic tool for some exciton spectra.