Improved insights in time-resolved photoelectron imaging.

Time-resolved photoelectron imaging (TRPEI) is a highly differential technique for the detailed study of non-adiabatic energy redistribution dynamics operating in the electronically excited states of molecules following the absorption of ultraviolet light. This Perspective briefly reviews the main elements of the TRPEI method but also seeks to address some of its limitations. With the help of various examples drawn from our own recent work, we illustrate some of the challenges commonly encountered during the analysis and interpretation of experimental data and introduce some initial thoughts on approaches to help deal with them. We also discuss some novel methods that aim to expand the capabilities and utility of the TRPEI technique by extending the observation window along the photochemical reaction coordinate(s) and improving the temporal resolution. Given the widespread use of TRPEI and related ultrafast spectroscopies, we anticipate that this Perspective will be of broad interest to a sizeable research community. Furthermore, we hope it will also serve as a useful overview for those engaging with this topic for the first time.