Picosecond laser chemistry

Figure 5. Schematic diagram of a time-resolved fluorescence spectrometer using a picosecond laser as an excitation source. Inset diagram intensity/time/ wavelength surface for poly (acenaphthalene) in benzene at 20°C. Excitation wavelength 295 nm. (Reproduced with permission from Ref. 21. Copyright 1987 Chemistry in Australia.)...

Robinson, G. W., Caughey, T. A., Auerbach, R. A. Picosecond emission spectroscopy with an ultraviolet sensitive streak camera. In Advances in Laser Chemistry/Springer Series in Chemical Physics. Tlewafl, A. H. (Ed.) p. 108, Berlin, Heidelberg, New York Springer 1978 Robinson, G. W. et al. J. MoL Struct 47, 221 (1978)... 

In conclusion, picosecond time-resolved studies of IVR in beam-isolated molecules has been very fruitful over the past six years. Together with high-resolution spectroscopic studies, the approach should help us further in unraveling the details of the dynamics of vibrational motion in large molecules and in chemical processes at low and high energies, so that one may ultimately direct the fate of energy redistribution in laser chemistry experiments. 

Picosecond Laser and Spectroscopy Laboratory of the Department of Physical Chemistry, State University, Nijenborgh 16, 9747 A G Groningen, The Netherlands... 

We can indeed claim that this is an example of photoselective laser chemistry. The competition between relaxation and reaction of photoex-cited electrons in clusters represented in Fig. 14(b) is reminiscent of the competition in many laser-induced chemical processes, stimulated by the selective absorption of one or more photons, such as photodissociation, photoionization, isomerization, and so forth in polyatomic molecules, where the coupling of many vibrational modes provides energy randomization and relaxation on picosecond time scales. 

Femtosecond Real-Time Spectroscopy of Small Molecules and Clusters attempts to give a detailed overview of a small part of this new and exciting field situated at the boundary between physics and chemistry. The main subject of this book is research into the ultrafast dynamics of gas-phase molecules and clusters after excitation with intense femtosecond or picosecond laser pulses. Many textbook-like examples are presented. 

The mechanisms proposed by both of these groups to explain the details of the chemistry of esters that give rise to short-lived nitrenium ions are not the only mechanisms that could fit these data. Further developments in this area will require application of picosecond spectroscopic methods to ion pairs generated by laser flash photolysis. 

This narrative echoes the themes addressed in our recent review on the properties of uncommon solvent anions. We do not pretend to be comprehensive or inclusive, as the literature on electron solvation is vast and rapidly expanding. This increase is cnrrently driven by ultrafast laser spectroscopy studies of electron injection and relaxation dynamics (see Chap. 2), and by gas phase studies of anion clusters by photoelectron and IR spectroscopy. Despite the great importance of the solvated/ hydrated electron for radiation chemistry (as this species is a common reducing agent in radiolysis of liquids and solids), pulse radiolysis studies of solvated electrons are becoming less frequent perhaps due to the insufficient time resolution of the method (picoseconds) as compared to state-of-the-art laser studies (time resolution to 5 fs ). The welcome exceptions are the recent spectroscopic and kinetic studies of hydrated electrons in supercriticaF and supercooled water. As the theoretical models for high-temperature hydrated electrons and the reaction mechanisms for these species are still rmder debate, we will exclude such extreme conditions from this review. 

During the last decade, the technology of laser-driven picosecond accelerators has been successfully applied to pulse radiolysis experiments in diverse areas of chemistry The reliability of the accelerators and their beam characteristics, and the development of real-time, non-destructive beam diagnostics to monitor them, have provided a... 

James R Wishart received a B.S. in Chemistry from the Massachusetts Institute of Technology in 1979 and a Ph.D. in Inorganic Chemistry from Stanford University in 1985 under the direction of Prof Henry Taube. After a postdoctoral appointment at Rutgers University, in 1987 he joined the Brookhaven National Laboratory Chemistry Department as a Staff Scientist in the Radiation Chemistry Group. He founded and presently supervises the BNL Laser-Electron Accelerator Facility for picosecond electron pulse radiolysis. His research interests include ionic liquids, radiation chemistry, electron transfer, and new technology and techniques for pulse radiolysis. He has authored over 90 papers and chapters, and is the co-editor of Advances in Chemistry Series o. 254, Photoehemistry and Radiation Chemistry. 

The versatility of OMCDs and, of course, advances in laser technology have been responsible for the increasing numbers of applications of picosecond spectroscopy to problems in areas of physics, chemistry, and biology. 

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