TY  - JOUR
A1  - Süß, Jasmin
A1  - Wehner, Johannes G.
A1  - Dostál, Jakub
A1  - Engel, Volker
A1  - Brixner, Tobias
T1  - Mapping of exciton-exciton annihilation in a molecular dimer via fifth-order femtosecond two-dimensional spectroscopy
JF  - Journal of Physical Chemistry Letters
N2  - We present a theoretical study on exciton–exciton annihilation (EEA) in a molecular dimer. This process is monitored using a fifth-order coherent two-dimensional (2D) spectroscopy as was recently proposed by Dostál et al. [Nat. Commun. 9, 2466 (2018)]. Using an electronic three-level system for each monomer, we analyze the different paths which contribute to the 2D spectrum. The spectrum is determined by two entangled relaxation processes, namely, the EEA and the direct relaxation of higher lying excited states. It is shown that the change of the spectrum as a function of a pulse delay can be linked directly to the presence of the EEA process.
KW  - exciton-exciton
KW  - Exziton
KW  - Spektroskopie
KW  - EEA
KW  - 2Dimensionale Spektroskopie
KW  - exciton
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-178420
UR  - https://aip.scitation.org/doi/full/10.1063/1.5086151
N1  - This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Süß et al., J. Chem. Phys. 150, 104304 (2019); https://doi.org/10.1063/1.5086151 and may be found at https://doi.org/10.1063/1.5086151.
VL  - 150
IS  - 10
ER  - 
TY  - JOUR
A1  - Hoche, Joscha
A1  - Schulz, Alexander
A1  - Dietrich, Lysanne Monika
A1  - Humeniuk, Alexander
A1  - Stolte, Matthias
A1  - Schmidt, David
A1  - Brixner, Tobias
A1  - Würthner, Frank
A1  - Mitric, Roland
T1  - The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes
JF  - Chemical Science
N2  - Fluorophores with high quantum yields are desired for a variety of applications. Optimization of promising chromophores requires an understanding of the non-radiative decay channels that compete with the emission of photons. We synthesized a new derivative of the famous laser dye 4-dicyanomethylen-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM),i.e., merocyanine 4-(dicyanomethylene)-2-tert-butyl-6-[3-(3-butyl-benzothiazol-2-ylidene)1-propenyl]-4H-pyran   (DCBT).   We   measured fluorescence lifetimes and quantum yields in a variety of solvents and found a trend opposite to the energy gap law.This motivated a theoretical investigation into the possible non-radiative decay channels. We propose that a barrier to a conical intersection exists that is very sensitive to the solvent polarity. The conical intersection is characterized by a twisted geometry which allows a subsequent photoisomerization. Transient absorption measurements confirmed the formation of a photoisomer in unpolar solvents, while the measurements of fluorescence quantum yields at low temperature demonstrated the existence of an activation energy barrier.
KW  - solvent-dependent fluorescence yield
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198707
UR  - https://doi.org/10.1039/C9SC05012D
VL  - 10
ER  - 
TY  - JOUR
A1  - Mueller, Stefan
A1  - Lüttig, Julian
A1  - Malý, Pavel
A1  - Ji, Lei
A1  - Han, Jie
A1  - Moos, Michael
A1  - Marder, Todd B.
A1  - Bunz, Uwe H. F.
A1  - Dreuw, Andreas
A1  - Lambert, Christoph
A1  - Brixner, Tobias
T1  - Rapid multiple-quantum three-dimensional fluorescence spectroscopy disentangles quantum pathways
JF  - Nature Communications
N2  - Coherent two-dimensional spectroscopy is a powerful tool for probing ultrafast quantum dynamics in complex systems. Several variants offer different types of information but typically require distinct beam geometries. Here we introduce population-based three-dimensional (3D) electronic spectroscopy and demonstrate the extraction of all fourth- and multiple sixth-order nonlinear signal contributions by employing 125-fold (1⨯5⨯5⨯5) phase cycling of a four-pulse sequence. Utilizing fluorescence detection and shot-to-shot pulse shaping in single-beam geometry, we obtain various 3D spectra of the dianion of TIPS-tetraazapentacene, a fluorophore with limited stability at ambient conditions. From this, we recover previously unknown characteristics of its electronic two-photon state. Rephasing and nonrephasing sixth-order contributions are measured without additional phasing that hampered previous attempts using noncollinear geometries. We systematically resolve all nonlinear signals from the same dataset that can be acquired in 8 min. The approach is generalizable to other incoherent observables such as external photoelectrons, photocurrents, or photoions.
KW  - Atomic and molecular interactions with photons
KW  - Optical spectroscopy
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-202529
VL  - 10
ER  -