Freiburg 2024 – scientific programme
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MO: Fachverband Molekülphysik
MO 16: Ultrafast Dynamics I
MO 16.6: Talk
Wednesday, March 13, 2024, 15:45–16:00, HS 3044
Excited state dynamics of BN-9,10-naphthalene: The impact of replacing CC by BN — •Floriane Sturm, Michael Bühler, Christoph Stapper, Johannes Schneider, Holger Helten, Ingo Fischer, and Merle Röhr — Julius-Maximilians-Universität Würzburg
Substituting CC by BN units is an excellent means to modify the optoelectronic properties of PAHs.1-3 In our research, the excited state spectroscopy and dynamics of BN-9,10-naphthalene were studied by picosecond time-resolved photoionization in a supersonic jet. A REMPI spectrum reveals the S1 origin at 33841 cm−1, which is in very good agreement with theory. Several vibrational bands were resolved and assigned by comparison with computations. A [1+1] photoelectron spectrum via the S1 origin yielded an adiabatic ionization energy of 8.27 eV. Selected vibrational bands were investigated by pump-probe photoionization. While the origin as well as several low-lying vibronic states exhibit lifetimes in the ns-range, a monoexponential decay is observed at higher excitation energies, ranging from 400 ps, at +1710 cm−1 to 13 ps at +3360 cm−1. Based on quantum chemical calculations, the deactivation is attributed to a conical intersection to the ground state. In order to access it, an energy barrier has to be passed, which requires sufficient excess energy.
[1] M. J. D. Bosdet, W. E. Piers, Can. J. Chem., 87, 8-29 (2009).
[2] H. L. van de Wouw, R. S. Klausen, J. Org. Chem., 84, 1117-1125 (2019).
[3] Z. Liu, T. B. Marder, Angew. Chem. Int. Ed., 47, 242-244 (2008).
Keywords: supersonic jet; excited state dynamics; picosecond time resolution; pump-probe photoionization; velocity map imaging