Laser selective chemistry

Zewail A H 1980 Laser selective chemistry—is it possible Phys. Today Nov, 27-33... 

Laser Selective Chemistry Is It Possible A. H. Zewail, Phys. Today 33, 27 (1980). 

R. D. Levine As emphasized by the speakers on femtosecond pumping schemes, an important point is that the initial excitation is localized within the Franck-Condon regime. The question is whether the sheer localization can be used to advantage to induce laser-selective chemistry (K. L. Kompa and R. D. Levine, Acc. Chem. Res. 27, 91 (1994)]. As we understand better the topography of potential-energy surfaces for polyatomic molecules, it may be possible to launch the system with such initial conditions that it will, of its own accord, proceed to cross a particular transition state and so exit toward a particular set of products. 

Other hand, the potential success of laser selective chemistry depends on the existence of metastable vibrational energy distributions. Structural information about the nature and effects of the weak bonding interaction are obtained from spectral shifts, intensities and, in favorable cases, rotational structure in the photodissociation spectra. Rotational structure, vibrational frequencies and band intensities are all influenced by the intramolecular potential. 

D. Goswami, C.W. Hillegas, J.X. Tull, and W.S. Waren, Generation of Shaped Femtosecond Laser Pulses New Appoaches to Laser Selective Chemistry in Femtosecond Reaction Dynamics, D.A. Wiersma (ed.) (North-HoIIand, Amsterdam, 1994), p 291. 

Zewail, A. H. (1980). Laser-selective chemistry is it possible Phys. Today 33,27. 

Modem photochemistry (IR, UV or VIS) is induced by coherent or incoherent radiative excitation processes [4, 5, 6 and 7]. The first step within a photochemical process is of course a preparation step within our conceptual framework, in which time-dependent states are generated that possibly show IVR. In an ideal scenario, energy from a laser would be deposited in a spatially localized, large amplitude vibrational motion of the reacting molecular system, which would then possibly lead to the cleavage of selected chemical bonds. This is basically the central idea behind the concepts for a mode selective chemistry , introduced in the late 1970s [127], and has continuously received much attention [10, 117. 122. 128. 129. 130. 131. 132. 133. 134... 

Quack M 1991 Mode selective vibrational redistribution and unimolecular reactions during and after IR-laser excitation Mode Selective Chemistry ed J Jortner, R D Levine and B Pullman (Dordrecht Kluwer) pp 47-65... 

This leads to the possibiUty of state-selective chemistry (101). An excited molecule may undergo chemical reactions different from those if it were not excited. It maybe possible to drive chemical reactions selectively by excitation of reaction channels that are not normally available. Thus one long-term goal of laser chemistry has been to influence the course of chemical reactions so as to yield new products unattainable by conventional methods, or to change the relative yields of the products. 

Mode-selective chemistry The use of laser beams to control the outcome of a chemical reaction by exciting specific energy states of the reactants. 

Hence for producing expensive and sensitive chemicals, vdW complexes laser-induced chemistry may become a useful method, which will fulfill the dream of site-selective chemistry. ... 

The possibility of controlling chemical reactions by selective excitation of the reactants and by coherent control of the excited state wavefunction (as illustrated in Sect. 10.1.4) may open a new fascinating field of laser-induced chemistry. 

The reactions in Equations (22.1) and (22.2) were prepared by generating the H atoms with a microwave discharge and the HOD molecule in selected overtones by using laser excitation in the visible. The reaction in Equation (22.1) was prepared with four quanta in the H-OD stretch and produced nearly pure H2 -I- OD products. Conversely, when the HO-D stretch was prepared with five quanta, nearly pure HD -f OH products were found. The conclusion is that mode-selective chemistry can be realized by localizing vibrational... 

The formation and dissociation of chemical bonds is of prime concern in chemistry, and with the advent of ultrafast high-intensity lasers, selective bond dissociation using appropriate laser pulses as molecular tweezers and scissors has received extensive and intense attention. - Theoretical approaches to laser-assisted control of chemical reactions have kept pace and demonstrated remarkable success, with experimental results reinforcing the theoretical ideas. The development of... 

TUMOUR DESTRUCTION USING LASER-INDUCED CHEMISTRY (SELECTIVE RELEASE OF SINGLET OXYGEN)... 

Levis RJ, Rabitz H (2002) Closing the loop on bond selective chemistry using tailored strong field laser pulses. J Phys Chem A 106 6427... 

ABSTRACT. Selective chemical reactivity has played a long and vital role in the development of laser technology. Some recent examples of selective reactivity as applied to the understanding of rare gas halide excimer lasers and the search for novel chemically driven lasers are discussed. The future of selective chemistry as a component of laser development is projected. 

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