TY  - JOUR
A1  - Knorr, Johannes
A1  - Rudolf, Philipp
A1  - Nuernberger, Patrick
T1  - A comparative study on chirped-pulse upconversion and direct multichannel MCT detection
N2  - A comparative study is carried out on two spectroscopic techniques employed to detect ultrafast absorption changes in the mid-infrared spectral range, namely direct multichannel detection via HgCdTe (MCT) photodiode arrays and the newly established technique of chirped-pulse upconversion (CPU). Whereas both methods are meanwhile individually used in a routine manner, we directly juxtapose their applicability in femtosecond pump-probe experiments based on 1 kHz shot-to-shot data acquisition. Additionally, we examine different phase-matching conditions in the CPU scheme for a given mid-infrared spectrum, thereby simultaneously detecting signals which are separated by more than 200 cm−1.
KW  - Ultrafast spectroscopy
KW  - Upconversion
KW  - infrared spectroscopy
KW  - Lithium niobate
KW  - CCD, charge-coupled device
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-111334
ER  - 
TY  - JOUR
A1  - Brixner, Tobias
A1  - Koch, Federico
A1  - Kullmann, Martin
A1  - Selig, Ulrike
A1  - Nuernberger, Patrick
A1  - Götz, Daniel C. G.
A1  - Bringmann, Gerhard
T1  - Coherent two-dimensional electronic spectroscopy in the Soret band of a chiral porphyrin dimer
JF  - New Journal of Physics
N2  - Using coherent two-dimensional (2D) electronic spectroscopy in fully noncollinear geometry, we observe the excitonic coupling of β,β'-linked bis[tetraphenylporphyrinato-zinc(II)] on an ultrafast timescale in the excited state. The results for two states in the Soret band originating from an excitonic splitting are explained by population transfer with approximately 100 fs from the energetically higher to the lower excitonic state. This interpretation is consistent with exemplary calculations of 2D spectra for a model four-level system with coupling.
KW  - optics
KW  - quantum optics
KW  - laser
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-96139
ER  - 
TY  - JOUR
A1  - Verma, Pramod Kumar
A1  - Steinbacher, Andreas
A1  - Schmiedel, Alexander
A1  - Nuernberger, Patrick
A1  - Brixner, Tobias
T1  - Excited-state intramolecular proton transfer of 2-acetylindan-1,3-dione studied by ultrafast absorption and fluorescence spectroscopy
JF  - Structural Dynamics
N2  - We employ transient absorption from the deep-UV to the visible region and fluorescence upconversion to investigate the photoinduced excited-state intramolecular proton-transfer dynamics in a biologically relevant drug molecule, 2-acetylindan-1,3-dione. The molecule is a ß-diketone which in the electronic ground state exists as exocyclic enol with an intramolecular H-bond. Upon electronic excitation at 300 nm, the first excited state of the exocyclic enol is initially populated, followed by ultrafast proton transfer (≈160 fs) to form the vibrationally hot endocyclic enol. Subsequently, solvent-induced vibrational relaxation takes place (≈10 ps) followed by decay (≈390 ps) to the corresponding ground state.
KW  - time resolved spectroscopy
KW  - ground states
KW  - fluorescence spectra
KW  - absorption spectra
KW  - ultraviolet light
KW  - hydrogen bonding
KW  - excited states
KW  - reaction mechanisms
KW  - fluorescence
KW  - solvents
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-181301
VL  - 3
ER  - 
TY  - JOUR
A1  - Knorr, Johannes
A1  - Sokkar, Pandian
A1  - Schott, Sebastian
A1  - Costa, Paolo
A1  - Thiel, Walter
A1  - Sander, Wolfram
A1  - Sanchez-Garcia, Elsa
A1  - Nuernberger, Patrick
T1  - Competitive solvent-molecule interactions govern primary processes of diphenylcarbene in solvent mixtures
JF  - Nature Communications
N2  - Photochemical reactions in solution often proceed via competing reaction pathways
comprising intermediates that capture a solvent molecule. A disclosure of the underlying
reaction mechanisms is challenging due to the rapid nature of these processes and the
intricate identification of how many solvent molecules are involved. Here combining
broadband femtosecond transient absorption and quantum mechanics/molecular mechanics
simulations, we show for one of the most reactive species, diphenylcarbene, that the
decision-maker is not the nearest solvent molecule but its neighbour. The hydrogen bonding
dynamics determine which reaction channels are accessible in binary solvent mixtures at
room temperature. In-depth analysis of the amount of nascent intermediates corroborates
the importance of a hydrogen-bonded complex with a protic solvent molecule, in striking
analogy to complexes found at cryogenic temperatures. Our results show that adjacent
solvent molecules take the role of key abettors rather than bystanders for the fate of the
reactive intermediate.
KW  - Reaction kinetics and dynamics
KW  - Photochemistry
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-165954
VL  - 7
ER  -