ABSTRACT
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.1-90 Theoretical approaches to laser-assisted control of chemical reactions have kept pace and demonstrated remarkable success,24,28 with experimental results17,18,20,26 reinforcing the theoretical ideas. The development of
7.1 Introduction .................................................................................................. 113 7.2 Method .......................................................................................................... 114
7.2.1 Diatomic Systems: IBr and HI .......................................................... 114 7.2.2 Triatomic System: HOD ................................................................... 117 7.2.3 Triatomic System: 18O16O16O ............................................................ 118
7.3 Results and Discussion ................................................................................. 119 7.3.1 Selective Control of IBr Photodissociation ....................................... 119 7.3.2 Selective Control of HI Photodissociation ........................................ 125 7.3.3 Selective Control of HOD Photodissociation ................................... 129 7.3.4 Selective Control of 18O16O16O Photodissociation ............................ 154
7.4 Concluding Remarks .................................................................................... 157 Acknowledgments .................................................................................................. 159 References .............................................................................................................. 159
theory and experiments has largely focused on the design of appropriate laser pulses to obtain the desired product from photodissociation reactions, often requiring field attributes that may not be realized on the basis of chemical considerations and may also be difficult to reproduce under normal laboratory conditions.6-10,21,24,28 The photodissociation yield has, however, also been found to be extremely sensitive to the initial vibrational state from which photolysis is induced, and results for H2
+25, HI,22,29 HCl,19 and HOD3,4,23,46,49,55-61 reveal a crucial role for the initial state of the system in product selectivity and enhancement. This critical dependence on the initial vibrational state indicates that a suitable choice of a single optimal initial vibrational state or an optimized linear superposition of the field-free vibrational states may be another route to photodynamic control of selective bond dissociation. The different established theoretical methods that use lasers to control chemical reactions have been reviewed recently6-13,15,23,24,27,28 and are based on field design. It is our purpose in this contribution to present results from our work that provide encouraging alternatives for selective control of bond dissociation using simple laser pulses, in conjunction with the use of an appropriately chosen single field-free vibrational state3,4,34,57-61 or an optimal linear combination4,14,30-33,57,58 thereof as the initial state to be subjected to this simple laser pulse.
