AG Zinth - Projects

LMU München
Fakultät für Physik



(c) 2002 BMO

Ultrafast Fluorescence Spectroscopy - The Kerr-Gate Setup
(Development of most modern methods in quantum optics for studies of ultra fast processes in chemistry and biology)

Our aim is to resolve the fastest steps in photochemistry and photobiology using femtosecond laser pulses. As fluorescence spectroscopy selectively monitors the dynamics of molecules in the primarily excited state it perfectly complements the often used transient absorption technique. Employing femtosecond time resolution we are capable of tracking the first steps after photo-excitation and getting detailed information about the excited state topology.
Some processes we have investigated so far:

  • fluorescence lifetimes down to the 100 fs time scale (beta-carotene)
  • ultrafast intersystem crossing in aromatic ketones
  • initial processes in photo-reactive systems (bacteriorhodopsin, azobenzene)
  • ultrafast solvation dynamics

We time resolve the fluorescence using a optical Kerr-gate setup. Here, the fluorescence light emitted by a molecule which has been excited with a femtosecond laser pulse is imaged onto this gate. This consists of two crossed polarizers and a Kerr-medium (a fused silica glass plate). A second laser pulse - the gate pulse - is overlapped with the fluorescence in the Kerr-medium. The birefringence of the Kerr-medium induced by this gate pulse opens the Kerr-cell for the duration of this pulse. Using a variable delay line this allows to record the fluorescence intensity at defined times after excitation. Since the fluorescence light is spectrally dispersed after the Kerr cell a complete spectrum can be recorded at a time.
Some technical details: We use a Clark CPA2001 system to pump a collinear optical parametrical amplifier (OPA) and a non-collinear OPA (NOPA). The OPA delivers the gate pulses at 1100 nm and the NOPA is used as excitation source for our samples. Employing second harmonic generation and large aperture UV-vis optical elements we are able to excite samples from 200 nm to 680 nm and detect fluorescence from 300 nm to 1000 nm. The time resolution of our set-up is ~ 70 fs.

Previous coworkers:  Gerald Ryseck
Bjoern Heinz
Peter Gilch

Publications:  "Excited State Processes of Nitrobenzaldehydes Probed by Ultrafast Fluorescence and Absorption Spectroscopy"
B. Heinz, T. Schmierer, S. Laimgruber, P. Gilch
J. Photochem. Photobiol. A: Chemistry, 199 (2008), 274-281

"Comparing a Photoinduced Pericyclic Ring Opening and Closure: Differences in the Excited State Pathways"
B. Heinz, S. Malkmus, S. Laimgruber, S. Dietrich, C. Schulz, K. Rück-Braun, M. Braun, W. Zinth, P. Gilch
J. Am. Chem. Soc. 129 (2007) 8577

"Ultrafast Photochromism: Structural and Electronic Dynamics of Indolyl Fulgimides"
M. Braun, S. Malkmus, F.O. Koller, B. Heinz, W. Zinth, C. Schulz, S. Dietrich, K. Rück-Braun
Ultrafast Phenomena XV, Springer Series in Chem. Physics 88, Eds. Andrew M. Weiner and R. J. Dwayne Miller, Springer-Verlag, Berlin (2006) 291-293

"Excited-state dynamics of bacteriorhodopsin probed by broadband femtosecond fluorescence spectroscopy"
B. Schmidt, C. Sobotta, B. Heinz, S. Laimgruber, M. Braun, P. Gilch
Biochimica et Biophysica Acta 1706 (2005) 165-173

"Monitoring an ultrafast photo-isomerization by femtosecond fluorescence, absorption, and IR spectroscopy"
P. Gilch, B. Schmidt, C. Sobotta, M. Braun, F. Koller, T. Schrader, A. Sieg, W. Schreier, W. Zinth
Ultrafast Phenomena XIV, Springer Series in Chem. Physics 79, Eds. T. Kobayashi, T. Okada, T. Kobayashi, K. A. Nelson, S. De Silvestri, Springer-Verlag, Berlin (2005), 462 - 464

"Femtosecond fluorescence and absorption dynamics of
an azobenzene with a strong push-pull substitution "

B. Schmidt, C. Sobotta, S. Malkmus, S. Laimgruber, M. Braun, W. Zinth, P. Gilch
Journal of Physical Chemistry A 108 (2004) 4399-4404

"A broadband Kerr shutter for femtosecond
fluorescence spectroscopy"

B. Schmidt, S. Laimgruber, W. Zinth, P. Gilch
Appl. Phys. B 76 (2003) 809-814

"Femtosecond Fluorescence Lifetimes Determined by an Intrinsic Raman Gate"
Q. An, W. Zinth, P. Gilch
Ultrafast Phenomena XIII, Springer Series in Chem. Physics 71, Proceedings of the 13th International Conference, Eds. R.D. Miller, M.M. Murnane, N.F. Scherer, A.M. Weiner, Springer, Berlin (2002) 435 - 437

"In situ determination of fluorescence lifetimes via inverse Raman scattering"
Q. An, W. Zinth, P. Gilch
Opt. Comm. 202 (2002) 209-216

"Femtosekundenfluoreszenzspektroskopie mit Hilfe des Kerr-Effekts -Entwicklung und Charakterisierung"
Bernhard Schmidt
Diploma thesis, 2001

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Letzte Änderung: 2024-06-17 19:32