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Accueil > Séminaires > Année 2023 > Séminaire d’Audrey Scognamiglio

Séminaire d’Audrey Scognamiglio

Institute of Physics, University of Freiburg, Germany

par Martrenchard-Barra Séverine - 20 juin 2023

Ultrafast electronic relaxation of tetracene in the gas phase : the role of non-adiabatic couplings

Polyacenes are promising systems for application in organic photovoltaics, given their potential to produce multiple charge carriers from a single absorbed photon in a process known as singlet fission [1]. The ultrafast excitation dynamics of PAH following the absorption of a photon in the visible to the UV range provides a fundamental understanding of the underlying molecular energetics, and sheds light on the role of the non-adiabatic couplings in the electronic and nuclear relaxation.
We present a femtosecond time-resolved photoion and photoelectron study of the free tetracene molecule excited into its brightest singlet state, followed by a fast electronic relaxation into lower lying singlet states (Fig. 1). Since the excitation into higher lying states goes along with the production of thermal electrons [2], unavoidable multiphoton absorption, and the possibility for the electrons to correlate to different cationic states, corresponding experiments are challenging. However, experimental results are in agreement with theoretical investigations of the non-adiabatic relaxations in polyacenes which were realized independently [3].

Fig. 1 3D representation of the thermal background subtracted photoelectron spectra as a function of the pump-probe delay. Relevant photoelectron features are indicated with the black stars.

[1] T. M. Clarke and J. R. Durrant, Chemical Reviews, 110, 6736-6767 (2010).
[2] J. O. Johansson, G. G. Henderson and E. E. B. Campbell, J. Phys. Chem. A, 118, 8067-8076 (2014)
[3] E. Posenitskiy, M. Rapacioli, B. Lepetit, D. Lemoine and F. Spiegelman, Phys. Chem. Chem. Phys. 21. 12139 (2019)

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