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  - 
TY  - JOUR
A1  - Malý, Pavel
A1  - Brixner, Tobias
T1  - Fluorescence‐Detected Pump–Probe Spectroscopy
JF  - Angewandte Chemie International Edition
N2  - We introduce a new approach to transient spectroscopy, fluorescence‐detected pump–probe (F‐PP) spectroscopy, that overcomes several limitations of traditional PP. F‐PP suppresses excited‐state absorption, provides background‐free detection, removes artifacts resulting from pump–pulse scattering, from non‐resonant solvent response, or from coherent pulse overlap, and allows unique extraction of excited‐state dynamics under certain conditions. Despite incoherent detection, time resolution of F‐PP is given by the duration of the laser pulses, independent of the fluorescence lifetime. We describe the working principle of F‐PP and provide its theoretical description. Then we illustrate specific features of F‐PP by direct comparison with PP, theoretically and experimentally. For this purpose, we investigate, with both techniques, a molecular squaraine heterodimer, core–shell CdSe/ZnS quantum dots, and fluorescent protein mCherry. F‐PP is broadly applicable to chemical systems in various environments and in different spectral regimes.
KW  - femtochemistry
KW  - FL spectroscopy
KW  - time-resolved spectroscopy
KW  - transient absorption
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-244811
VL  - 60
IS  - 34
SP  - 18867
EP  - 18875
ER  -