Welcome to the Web Site of the European Network on REACTION DYNAMICS: Experimental and Theoretical Studies on the Dynamics of Reactions of Atoms and Radicals of Fundamental and Practical Importance

REACTION DYNAMICS is part of the Improving Human Potential (IHP) projects in Fifth Framework Programme of the European Commission. Co-ordinator is Prof. P. Casavecchia. Contract number is: HPRN-CT-1999-00007. Operation of the Network started on March 1, 2000. The planned duration is 4 years.
 

    The principal aim is to advance significantly our knowledge of the dynamics of elementary chemical reactions which are also of relevance in areas of practical importance, such as combustion-, atmospheric-, and astro-chemistry.
    To this end, we have combined, in an unprecedented synergistic effort, internationally distinguished teams of experimentalists and theoreticians. They will employ state-of-the-art experimental techniques, based on sophisticated molecular beam and laser spectroscopic methods, state-of-the-art quantum chemical methods for calculating the potential energy surfaces that describe the reactions studied experimentally, and state-of-the-art quantum and classical methods for performing computations of scattering properties and thermal rate constants on these surfaces and for also predicting quantities difficult to measure. The majority of processes to be studied are reactions which involve transient species (atoms and radicals), of central chemical importance, with simple molecules, and which have escaped so far detailed experimental and theoretical dynamic investigation. Experimentally, the methods to be used have been established very recently in the participating laboratories. Theoretically, the effort will also tackle what are two major challenges for the next decade: (i) the inclusion of multiple surfaces and the role of electronically non-adiabatic coupling in reaction dynamics, and (ii) the formidable dimensionality problem, which represents the bottleneck for progress in the treatment of more complex reactive systems.
 

     The network consists of the following participants:
 

The joint research programme has three main aims:
- We plan to use state-of-the-art powerful complementary experimental techniques to study the detailed dynamics of important chemical reactions of great relevance from both fundamental and practical points of view.
- We plan to use state-of-the-art quantum chemical methods for calculating the potential energy surfaces (PESs) which describe the collision processes studied experimentally, and on these surfaces we plan to carry out scattering calculations using state-of-the-art quantum mechanical as well as classical methods, in order to predict the quantities which are experimentally measured. The combination of the experimental and theoretical approaches has the goal of reaching an unprecedented level of understanding of molecular reactive collisions and then of the forces that drive chemical reactivity, a central theme of chemistry.
- The Network will provide an excellent and unique opportunity to train a group of young scientists through involvement in an exciting top quality scientific project in which the joint experimental and theoretical collaboration across eight  leading European laboratories is a distinctive characteristic. The young researchers will be working with state-of-the-art equipment, both experimental and theoretical, and will therefore acquire a wide range of scientific and technical skills.

We will focus on the following benchmark reactions:
                                             (1)         Cl(²P_3/2,1/2) + H₂ -> HCl + H
                                              (2)        O(¹D) + H₂ -> OH + H
                                              (3)        N(²D) + H₂ -> NH + H
                                              (4)        C(¹D) + H₂ -> CH + H
                                              (5)        OH +  H₂ -> H₂O + H
                                              (6)        OH + CO -> CO₂ + H

Reaction (1), the rate determining step in the H₂-Cl₂ chain reaction, has fascinated chemists since the past century and has played a central role in the development of fundamental gas-phase kinetics. It is also representative of a host of Cl abstraction reactions of interest in the atmosphere. Reactions (2)-(4) are also of interest in the ozone chemistry of the atmosphere, in combustion and in astrochemistry. The interest in the reactive scattering of the hydroxyl radical with the hydrogen molecule (reaction (5)) origins from several reasons. It represents the chain propagation step in the combustion of hydrogen and is the main source of water in hydrocarbon/air flames at normal pressure conditions. This reaction is also thought to be of major importance for the interstellar OH and H₂O masersin forming the regenerative step for the former and the active medium for the latter process. Besides these practical reasons, the full quantum mechanical treatment of this system, containing 3 light atoms, becomes feasible nowadays, being the reaction of choice for exact quantum-mechanical state-to-state scattering calculations on four-atom systems. Reaction (6) is the second most important reaction in combustion and is also of paramount importance in the atmosphere, since it represents the main removal pathway of the ubiquitous OH radicals; it is also of some relevance in astrophysics. Because of this practical interest, the kinetics of reactions (1-6) have been extensively studied, but, despite considerable theoretical and experimental work over the last decade, their dynamics is still not well understood. New, systematic measurements in a wide range of energies and examination of the stereodynamics using state-of-the-art techniques will be conducted to provide a detailed quantitative understanding of these processes and a robust data base for comparison with state-of-the-art theory. State-of-the-art theoretical studies are in turn essential for the understanding and interpretation of experimental measurements, as previous work as demonstrated (e.g., for F+H₂). A new theoretical approach capable to deal with the dimensionality problem (the most prominent current restriction on the theoretical side) will be developed in order to extend similar dynamics studies of more complex reactions, which are of relevance in practice (in particular in combustion and atmospheric chemistry).

tackle unsolved problems in current treatments of benchmark 3-atom reactions, e.g. the role of multiple PES and non-adiabatic effects on the reactions Cl(²P_3/2,1/2)+H₂ and O(¹D)+H₂.
extend the fundamental comparison between experiments and exact theory to systems characterized by a deep potential well between reactant and products, e.g. O(¹D)+H₂ leading to OH+H via the PES of H₂O, N(²D)+H₂ leading to NH+H via the PES of the NH₂ radical, and C(1D)+H₂ leading to CH+H via the PES of the CH₂ radical.
  explore in great detail two prototypical four-atom reactions, OH+H₂, OH+CO, NH+NO and their reverse, at the state-to-state level, by looking also at the inelastic part of the collisions.
  pave the way towards the understanding of more complex chemical systems.

To this end we have put together in this Network four leading experimental groups (in Europe and worldwide) and four leading  theoretical groups (in Europe and worldwide).