Femtosecond pump-probe spectroscopy

Ellington et al.40) used femtosecond pump-probe spectroscopy to probe directly the arrival of electrons injected into the TiOz film with near- and mid-IR that probe the absorption at 1.52 jum and in the range of 4.1-7.0 jUm. Their measurements indicate an instrument limited 50 fsec upper limit on the electron injection time. These observations suggest that electron injection from Dye 2 to... 

Stock, G. and Domcke, W. (1990). Theory of femtosecond pump-probe spectroscopy of ultrafast internal conversion processes in polyatomic molecules, J. Opt. Soc. Am. B 7, 1971. 

Theoretical papers on effects directly observable in the very short time regime are notable in this years collection. The theory of femtosecond pump-probe spectroscopy of ultrafast Internal conversion processes in polyatomic molecules has been developed using the behaviour of the excited pyrazine molecule as an example . The solvation dynamics for an ion pair in a polar solvent can now be examined by the time dependence of fluorescence and by direct observation of photoinduced charge... 

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. 

The FuP group recently studied the photodissociation of Cr(CO)g with femtosecond pump-probe spectroscopy. Fu(i s results indicate that all fragment ions emerge from the photochemistry with an oscillation of the same period and phase,... 

K. Yokoyama, C. Silva, D.-H. Son, P.K. Walhout and P.F. Barbara, Detailed Investigation of the Femtosecond Pump-Probe Spectroscopy of the Hydrated Electron, J. Phys. Chem. A, 102 (1998), 6957. 

Fig. 6.8 Femtosecond pump-probe spectroscopy of diiodoBODIPY (10). (a) Inverted absorption spectrum (6) and transient absorption spectra at 0.5 (1), 20 (2), 50 (3), 110 (4), and 350 (5) ps delay between pump and probe pulses, (b) Differential absorption spectra of intermediate states obtained after modeling the experimental data by a three-exponential equation (see text) that is convoluted with the instrumental response function (1) zero delay (sum of all amplitudes, S2 state), (2) ultrafast relaxation of the S2 state (sum of A2, A3, A4 amplitudes), (3) thermalized Sj state (sum of A3 and A4 amplitudes), (4) Tj state (A4 amplitude). Reprinted with permission from [24]...

The high costs associated with specialist ultrafast laser techniques can make their purchase prohibitive to many university research laboratories. However, centralised national and international research infrastructures hosting a variety of large scale sophisticated laser facilities are available to researchers. In Europe access to these facilities is currently obtained either via successful application to Laser Lab Europe (a European Union Research Initiative) [35] or directly to the research facility. Calls for proposals are launched at least annually and instrument time is allocated to the research on the basis of peer-reviewed evaluation of the proposal. Each facility hosts a variety of exotic techniques, enabling photoactive systems to be probed across a variety of timescales in different dimensions. For example, the STFC Central Laser Facility at the Rutherford Appleton Laboratory (UK) is home to optical tweezers, femtosecond pump-probe spectroscopy, time-resolved stimulated and resonance Raman spectroscopy, time-resolved linear and non-linear infrared transient spectroscopy, to name just a few techniques [36]. 

The spectroscopic tool to be considered here is femtosecond pump/probe spectroscopy. This experimental technique uses two ultrashort laser pulses which are time-delayed with respect to each other. They are sent into a molecular sample and a signal is recorded as a function of the delay-time between the pulses. To be more specific, we assume the molecule to be in an inital state 0o) O). Here o) denotes the wave function for the nuclear motion and 0) the wave function of the electrons (the adiabatic separation of nuclear and electronic motion is assumed throughout). The pump pulse induces a transition and the resulting wave function which describes the molecule after the interaction with the electric field may be assigned as 0i l). We treat electronic excitation so that the molecule is prepared in another electronic state 1). After the pump pulse passed the sample, the molecule evolves unperturbed until the probe pulse starts interacting. This interaction results in a second excitation to (in our case) a final electronic state 2) with the respective nuclear wave function 1 2) The scheme just described is depicted in Figure 1 and illustrates the idea of many pump/probe experiments. 

The general complementarity of sensitivities in cw and femtosecond spectroscopy has been anticipated by Zewail [66] and it is verified for the Naa molecule excited to its electronic B state (see Sect. 3.2.4). This system has already been studied in great detail by various experimental and theoretical techniques such as cw two-photon ionization spectroscopy [68-70], femtosecond pump probe spectroscopy at high intensities [29, 30, 71], quantum ab initio studies [72-74], two-dimensional simulations of the pseudorot at ional progressions in the cw absorption spectra [75-78], and, finally, three-dimensional simulations by means of empirical potential-energy surfaces (PESs) [79, 80]. 

S. Rutz, E. Schreiber, and L. Woste, Femtosecond Pump Probe Spectroscopy on the K2 Molecule. Perturbations in Different Isotopomeres in Ultrafast Processes in Spectroscopy, O. Svelto, D. De Silvestri, and G. Denardo (eds.) (Plenum, New York, 1996), pp. 127-131. 

A. J. Dobbyn and J.M. Hutson, The Influence of the Ionisation Potential on the Simulated Ion Signal from Femtosecond Pump-Probe Spectroscopy , Chem. Phys. Lett. 236, 547 (1995). 

Y.J. Yan and S. Mukamel, Femtosecond Pump-Probe Spectroscopy of Polyatomic Molecules in Condensed Phases , Phys. Rev. A 41, 6485 (1990). 

R. de Vivie-Riedle and B. Reischl, Quantum Calculations of Femtosecond Pump-Probe Spectroscopy in K2 for Low Laser Field Intensities , Ber. Bun-senges. Phys. Chem. 99, 485 (1995). 

Nagarajan, V., Johnson, E., Williams, J.C., Parson, W.W. Femtosecond pump-probe spectroscopy of the B850 antenna complex of Rhodobacter sphaeroides at room temperature. J. Phys. Chem. B 103, 2297-2309 (1999)... 

Although much of the book focuses on physical theory, 1 have emphasized aspects of optical spectroscopy that are especially pertinent to molecular biophysics, and 1 have drawn most of the examples from this area. The book therefore covers topics that receive little attention in most general books on molecular spectroscopy, including exciton interactions, resonance energy transfer, single molecule spectroscopy, high-resolution fluorescence microscopy, femtosecond pump-probe spectroscopy, and photon echoes. It says less than is customary about atomic spectroscopy and about rotational and vibrational spectroscopy of... 

Henriksen, N. E. and V Engel (2001). Femtosecond pump-probe spectroscopy a theoretical analysis of transient signals and their relation to nuclear wave-packet motion. Int. Rev. Phys. Chem. 20, 93. 

Femtosecond Pump-Probe Spectroscopy of Photoinduced Tautomerism... 

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