2DSPEC - Simulating two-dimensional electronic spectroscopy: Capturing the complexities of photo-induced excitedstate molecular processes
Lead Research Organisation:
University College London
Department Name: Chemistry
Abstract
We aim to describe the 2-dimensional electronic spectroscopy (2DES) of biologically important macrocyclic molecules such as Zinc Pthalocyanines (ZnPCs) using first-principles computational methods. 2DES is a promising new technique to help unravel complicated excited-state dynamics, but at present new theoretical methods are required to help interpret the signals obtained. ZnPCs are a perfect target due to their rigidity and well-known photophysics. Due to their high symmetry (D4h), ZnPCs are subject to well-known Jahn-Teller (JT) and pseudo Jahn-Teller (PJT) interactions in the manifold of low-lying electronic states, in particular,
involving those of E symmetry. These JT and PJT interactions manifest themselves in the 2DES through the appearance of broad off diagonal peaks along with other electronic/vibrational contributions, making the spectra complicated. Discerning these vibronic contributions through the computation of 2DES signal by using the model JT/PJT Hamiltonians and comparing the structure of these signals with the experimentally determined one is crucial for a clear understanding of the 2DES spectroscopic map. Thus the main emphasis will be on unravelling the precise role of these vibronic coupling effects on the 2D signal. This will be done by a combination of computational and experimental work, with the former simulating the results of the latter. Overall, the planned systematic investigation of the 2D signal include mainly answering the following questions: (1) To what extent is dynamical information contained in the off-diagonal peaks? (2) How can the excited state excitations be treated? (3) Can we build simple model Hamiltonians that will allow detailed understanding? The study allows a detailed picture of the dynamics of photo-excited molecules to be obtained from 2DES and provides key understanding of the behavior of materials used in light-driven technologies and photoactivated biological processes such as photosynthesis.
involving those of E symmetry. These JT and PJT interactions manifest themselves in the 2DES through the appearance of broad off diagonal peaks along with other electronic/vibrational contributions, making the spectra complicated. Discerning these vibronic contributions through the computation of 2DES signal by using the model JT/PJT Hamiltonians and comparing the structure of these signals with the experimentally determined one is crucial for a clear understanding of the 2DES spectroscopic map. Thus the main emphasis will be on unravelling the precise role of these vibronic coupling effects on the 2D signal. This will be done by a combination of computational and experimental work, with the former simulating the results of the latter. Overall, the planned systematic investigation of the 2D signal include mainly answering the following questions: (1) To what extent is dynamical information contained in the off-diagonal peaks? (2) How can the excited state excitations be treated? (3) Can we build simple model Hamiltonians that will allow detailed understanding? The study allows a detailed picture of the dynamics of photo-excited molecules to be obtained from 2DES and provides key understanding of the behavior of materials used in light-driven technologies and photoactivated biological processes such as photosynthesis.