Two-dimensional spectroscopy for non-specialists

Detailed studies of the excitation dynamics in photosynthetic pigment-proteins require an application of a wide range of spectroscopic methods. From the later part of the previous century, pump–probe and time-resolved fluorescence spectroscopy provided an impressive amount of information. Being simple to grasp, these methods are well-understood and widely used by the photosynthesis research community. In the last fifteen years, two-dimensional (2D) spectroscopy was developed. It has significant advantages over other methods, in particular higher temporal resolution available and higher signal-to-noise ratio. Even though it provides considerable opportunities in research, both its experimental realization and theoretical description are rather complicated, making it somewhat difficult to understand and apply. This makes an unfortunate gap in the community, with spectroscopy experts being able to use the technique, but sometimes lacking the relevant biological knowledge, while biologists having that knowledge are dubious about 2D spectroscopy due to the complexity of the approach. This publication is an attempt to fill this gap by providing an accessible introduction to the concepts, principles and possible applications of the 2D spectroscopy, aimed at the biologically trained members of the photosynthesis research community. •2D spectroscopy is introduced to a wide audience.•Similarities and differences with pump–probe are highlighted.•Basic concepts, notation and conventions of 2D spectroscopy are described.