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  - 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  -