Femtosecond broadband pump-probe spectroscopy

A theory for the ultrafast pump-probe spectroscopy of large polyatomic molecules in condensed phases was developed in the work [15]. A multimode Brownian oscillator model was used to account for high-frequency molecular vibrations and local intermolecular modes as well as collective solvent motions. A semiclassical picture was provided using the density matrix in Liouville space. Conditions for the observation of quantum beats, spectral diffusion, and solvation dynamics (dynamic Stokes shift) are specified. 

and M13, aluminum mirrors PMl, 30° off-axis parabolic mirror PM2, 90° off-axis parabolic mirror MS, dielectric mirror used to cut off the fundamental wedged BS, wedged beam splitter, used to split the WLC into probe and reference beams PI, P2, P3, and P4, fused silica prisms LI and L2, lenses with focal lengths —50 and 75 mm, respectively [16], (Reproduced with permission.) 

The femtosecond pump-probe absorption spectroscopy was used for the investigation of the SI-photoisomerization of cis-stilbene in compressed solvents [20]. The authors of the work [21] demonstrated a technique for femtosecond time-resolved optical pump-probe spectroscopy that allowed to scan over a nanosecond time delay at a kilohertz scan rate without mechanical delay line. Two mode-locked femtosecond lasers with 1 GHz repetition rate were linked at a fixed difference frequency of =11 kHz. One laser delivers the pump pulses, the other provides the probe pulses. The techniques enabled high-speed scanning over a 1-ns time delay with a time resolution of 230 fs. 

Fluorescence Picosecond Time-Resolved Single Photon Counting 

Another example of the fluorescence decay measurements was given in Ref [11]. In the picosecond single-photon counting system, the sample was excited by a 

---

A detailed description of experimental setup of the femtosecond broadband pump-probe spectroscopy was given in Ref [11, 16]. Schematic representation of the experimental setup is shown in Figure 11.3. The combination of femtosecond broadband pump-probe spectroscopy, with an expanded spectral range, and picosecond fluorescence decay measurements permitted more detailed analysis of electron transfer dynamics [17-19]. The authors disentangled the various kinetic... 

The mechanism and dynamics of photoinduced charge separation and charge recombination have been investigated in synthetic DNA hairpins possessing donor and acceptor stilbenes (stilbene-4,4 -dicarboxylic acid, bis(3-hydroxypropyl)amide of stilbene-4,4 -dicarboxylic acid, bis(2-hydroxyethyl)stilbene 4,4 -diether) (Figure 11.1) using femtosecond broadband pump-probe spectroscopy, nanosecond transient absorption spectroscopy, and picosecond fluorescence decay measurements [11]. Nanosecond time-resolved spectra of stilbenes attached to DNA are shown in Figure 11.4. 

Abstract. We present a novel instrument combining femtosecond pump-probe spectroscopy with broadband detection and confocal microscopy. The system has 200-fs temporal resolution and 300-nm spatial resolution. We apply the instrument to map excited state dynamics in thin films of polyfluorene-polymethylethacrylate blends. 

---