An Introduction to Two-dimensional Electronic Spectroscopy and its Applications

Abstract: This thesis is written as an introductory compilation of two-dimensional electronic spectroscopy (2DES) and its applications. It introduces the concepts of 2DES where the aim is to provide an overview of the technique and a few of its more prominent applications for those who are not already familiar with the technique. 2DES is a third-order optics technique that utilizes three interactions with laser pulses and involves four transition dipole interactions and is thus a so-called four wave mixing (FWM) technique. A set-up utilizing a diffractive optics (DO) element and a local oscillator (LO) for heterodyne detection in a boxcar geometry is described. Theoretical description of 2DES is based on nonlinear response function formalism in the third order of perturbation theory. Basic concepts regarding the formalism and the projection of the mathematics as visualizable by double-sided Feynman diagrams will be explained. Research performed by multiple scientists has been focused on understanding the ultra-fast energy transfer efficiency in photosynthetic organisms and artificial systems. Some early studies suggested that the biological systems utilize electronic quantum coherent behaviour to improve the efficiency. This has however not been confirmed in other studies. One topic under inquiry is the very nature of coherent oscillations observed in the experiments. The chlorosome, Fenna-Matthew-Olson (FMO) protein and reaction centre (RC) of green sulphur bacteria has been of particular interest in the division of Chemical Physics and will therefore be mentioned throughout the discussion.