Molecular Reaction Dynamics Femtochemistry

One of the most exciting possibilities of ultrafast laser techniques is to follow the course of fundamental chemical reactions on the relevant timescale at which they occur. Previously, it was only possible to know the individual states of molecules A and B before reacting and the final state of the compound molecule AB. In contrast, the details of the chemical reaction can now be followed on a femtosecond scale with information on how chemical bonds are formed and broken. In particular, the existence of transition states has been demonstrated. This new field of science is frequently referred to as femtochemistry [9.191-9.204], for which A. Zewail was awarded a Nobel prize in chemistry (1999). 

A further type of reaction, which can be studied by femtosecond spectroscopy, is photoisomerisation, i.e., the optically induced transformation of one molecular structure into another. When cis-stilbene is excited by a femtosecond pulse, the central double bond is weakened allowing a rotation of the benzene rings to yield the trans-stilbene configuration (Fig. 9,37). The 

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The second advantage of a Q-first approach is that it opens the door to an early introduction of the modem and enthralling. Thermodynamics is perceived (with let s admit, some truth) to be pass6 the modem age is built around quantum theory and its implications for atoms, molecules, and materials. If we want to excite our students, then we are more likely to be able to do so with a quantum than with a thermodynamic function. Through the early introduction of quantum ideas we open the door to the presentation of modem topics, including spectroscopy, molecular reaction dynamics, femtochemistry, computation, and the emerging fields embraced by nanotechnology and nanoscience. In short, we have the opportunity to expose our students to the shock of the new. 

Manz, J. (1997). Molecular wave packet dynamics theory for experiments 1926-1996. In Femtochemistry and femtobiology ultrafast reaction dynamics at atomic-scale resolution (ed. V. Siindstrom), pp. 80-318. Imperial College Press, London. 

The variety of manifestations in time of coherent development of molecular dynamics also includes such phenomena as mono- and bimolecular chemical reactions. Thus, Seideman et al [342] suggest the idea of governing the yield of a reaction by suddenly creating coherent superposition of two states of the transient complex and applying a second pulse with fixed delay for the dissociation of the complex. The appearance of coherent beats in femtochemistry , in particular, at photodissociation, has been analyzed by Zewail (review [404]). 

Zewail AH. 2001. Femtochemistry recent progress in studies of dynamics and control of reactions and their transition states . In Atomic and Molecular Beams, Campargue R (ed.). Springer Berlin 415-476. 

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