Transient electronic absorption
Femtosecond Transient Electronic Absorption Spectroscopy (fs-TEAS) is the most versatile tool for the investigation of ultrafast processes and the main work horse in our group. The molecules in the sample solution contained in a thin (0.1 - 1 mm) flow cell or in a wire-guided free-flowing laminar liquid film are photo-excited by a 20 - 25 fs UV or VIS laser pulse from a wavelength-tunable non-collinear optical parametric amplifier (NOPA) equipped with a prism pulse compressor and an optional frequency-doubling stage. The optical response of the sample is then interrogated as function of pump-probe delay time by a broadband supercontinuum pulse in the UV-VIS or near-IR spectral region generated in sapphire or CaF2.
Schematic experimental setup for femtosecond broadband transient electronic absorption spectroscopy.
Our current setup has an additional beam path for single-color detection in the UV. (c) F. Temps
Thanks to a fast frame transfer (FFT) readout CCD camera, single-shot detection electronics at 1 kHz, and a pulse-to-pulse discriminator, we reach a broadband detection sensitivity of ΔOD ≤ 2 × 10-6, at a time resolution of Δt ~ 25 - 35 fs. An additional single-color probe beam (not shown in the figure below) allows us to follow the dynamics at deep-UV wavelengths with a detection sensitivity of ΔOD ≤ 5 × 10-6.
- K. Röttger, S. Wang, F. Renth, J. Bahrenburg, F. Temps, "A Femtosecond Pump-Probe Spectrometer for Dynamics in Transmissive Polymer Films", Appl. Phys. B 118, 185 - 193 (2015). DOI: 10.1007/s00340-014-5967-y
- K. Röttger, R. Siewertsen, F. Temps, "Ultrafast Electronic Deactivation Dynamics of the Rare Nucleobase Hypoxanthine", Chem. Phys. Lett. 536, 140 - 146 (2012). DOI: 10.1016/j.cplett.2012.03.106
- F. Renth, M. Foca, A. Petter, F. Temps, "Ultrafast Transient Absorption Spectroscopy of the Photo-Induced Z - E Isomerization of a Photochromic Furylfulgide," Chem. Phys. Lett. 428, 62 - 67 (2006).