4. Fs Transient Absorption Spectrometer
The chemical events are initiated by an actinic and resonant femtosecond laser pulse (pump) and the photophysical and photochemical events are probed by another ultrafast laser (probe) pulse. The pump-induced changes to the spectrum that are monitored simultaneously over a wide wavelength range by white light super-continuum and detected by the combination of a spectrograph and CCD-camera or photomultiplier tube. The setup features a time resolution of as short as 90 fs over a time window of 4 ns and a spectral range starting from 300 up to 1700 nm. When a longer time window is needed, the setup uses 2 or 3 delay lines and reaches 8-12 ns. This configuration is called “Extended transient absorption”
2 independent laser systems for excitation and 1 for probe, 2 independent detection schemes
The goal here is to interrogate the dynamics of the electronic ground, excited and intermediate states induced by a short excitation pulse. By recording transient absorption spectra, excited state processes like proton, electron and energy transfer can be revealed.