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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 12: Molecular Electronics and Excited State Properties I
CPP 12.3: Vortrag
Montag, 18. März 2024, 16:45–17:00, H 0106
Mapping Electronic Coupling in the Excited-State during Singlet Fission with Transient Two-Dimensional Electronic Spectroscopy — •Oskar Kefer1, Pavel V. Kolesnichenko1, Lukas Ahrens2, Jan Freudenberg2, Uwe H. F. Bunz2, and Tiago Buckup1 — 1PCI, Universität Heidelberg, Heidelberg — 2OCI, Universität Heidelberg, Heidelberg
Electronic coupling of an optically bright singlet- (S1S0) and a dark state, known as the correlated triplet pair (1[T1T1]), is a driving factor for singlet fission (SF). Detailed insight into the nature of the coupling is gained from theoretical considerations, due to the challenging nature of experimental confirmation. Transient two-dimensional electronic spectroscopy (transient 2DES) can directly study electronic-state correlations of singlet- and triplet excitons by utilizing an actinic-pump to launch SF beforehand.
We apply transient 2DES to spiro-linked SF-sensitizers, investigating the initial transformation of S1S0 to 1[T1T1]. Semi-quantum mechanical simulations allow extraction of relevant interaction parameters from measured cross-correlations of excited-states. Our findings indicate a direct SF-mechanism in the dimers, facilitated by non-adiabatic coupling between S1S0 and 1[T1T1]. A superposition of S1S0 and 1[T1T1] is formed, which shifts towards 1[T1T1], retaining the signatures of the coupled system even after completion. The experimental evidence reinforces the notion of the two interacting electronic states in equilibrium, a feat that was so far accessible only via computational methods.
Keywords: multidimensional; coupling; singlet fission; two dimensional electronic spectroscopy; transient