Elucidating photodynamics with ultrafast pulse sequences: pump-repump, multidimensional spectroscopy, and beyond

摘要

We demonstrate how diverse femtosecond spectroscopy approaches coalesce to a comprehensive understanding of photochemical reaction pathways, exemplarily for the ring-open isomers of merocyanine compounds. Pump-probe transient absorption spectroscopy discloses photo-induced ring closure, whereas coherent two-dimensional (2D) electronic spectra directly visualize whether there is photoisomerization. We further introduce coherent triggered-exchange 2D electronic spectroscopy, a versatile tool for analyzing excited states and associated reaction pathways, with the information from where the reaction started intrinsically preserved. Beyond that, third-order three-dimensional spectroscopy provides an intuitive picture for which reactants can be turned into which products, additionally exposing the reactive molecular modes connecting them.