Pump-probe experiment performed schematic

Time-resolved spectroscopy is performed using a pump-probe method in which a short-pulsed laser is used to initiate a T-jump and a mid-IR probe laser is used to monitor the transient IR absorbance in the sample. A schematic of the entire instrument is shown in Fig. 17.4. For clarity, only key components are shown. In the description that follows, only those components will be described. A continuous-wave (CW) lead-salt (PbSe) diode laser (output power <1 mW) tuned to a specific vibrational mode of the RNA molecule probes the transient absorbance of the sample. The linewidth of the probe laser is quite narrow (<0.5 cm-1) and sets the spectral resolution of the time-resolved experiments. The divergent output of the diode laser is collected and collimated by a gold coated off-axis... 

Figure 4. Schematic of pump-probe (saturated abs tion) experiment performed in single crystal PTS-polydiaceytlene platelet is the intense pump beam and Ej is the attenuated probe beam, is the relative time delay between the two beams, and DET is the photo-detector used to measure the transmitted probe power.

Nanosecond laser Flash Photolysis experiments were performed with 355 and 532 nm laser pulses from a Brilland-Quantel Nd YAG system (5 ns pulse width) in a front face (VIS) and side face (NIR) geometry using a pulsed 450 W XBO lamp as white light source. Similarly to the femtosecond transient absorption setup, a two beam arrangement was used. However, the pump and probe pulses were generated separately, namely the pump pulse stemming from the Nd YAG laser and the probe from the XBO lamp. A schematic representation of the setup is given below in Fig. 7.3. 0.5 cm quartz cuvettes were used for all measurements. 

The quantum yield of the radical pair triplet is also in the CP47-RC complexes clearly temperature dependent. We determined the yields for temperatures between 4 K and 200 K and modelled the yields by the exciton-radical pair equilibrium model of Schatz et al (note that relative yields are more accurate, since all experiments have been performed in the same setup with identical probe pump geometry for this reason, the shape of the temperature curve is more reliable than the absolute quantum yield values). The model is schematically reproduced in Fig.5. 

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