Abstract
Electronic coherent multidimensional spectroscopy (CMDS) allows detailed studies of ultrafast dynamics in systems with highly congested complicated spectral bands. A wide variety of experimental implementations have been developed4 emphasizing different strengths of the methodology.
Originally, the two-dimensional electronic spectroscopy (2DES) was based on phase-sensitive detection of a coherent photon-echo type signal generated by three laser pulses. During the past decade, four-pulse generated incoherent action detection has become popular.
The concept was originally developed for fluorescence detected 2DES (F-2DES). Later, numerous other incoherent action detection methods have been used, e.g., based on photoelectrons, photocurrents, and photoions.
In this Viewpoint we briefly summarize the various approaches to interpreting the F-2DES and present our view with the intension of resolving at least some of the existing controversial issues.