1) Could you explain the significance of your article to the non-specialist? 

The quantum phenomenon known as resonance is associated with temporary trapping of the energy in the internal degrees of freedom of a reaction intermediate. In the F+H2 reaction, the results of our quantum mechanical calculations reveal two interfering resonance pathways leading to the product HF to be scattered selectively in the same direction of the F atom hitting the H2 molecule. The origin of this quantum structure, recently observed in molecular beam experiments, has been explained applying the semiclassical complex angular momentum analysis appropriate to cope with the phenomenology observed in chemical reaction dynamics, a field which lies at the borderline where overall behaviour can be given an intuitive classical picture, over which quantum phenomena superpose. 

2) What has motivated you to conduct this work? 

Now that we and others have developed state-of-the-art computer codes which can accurately model chemical reactions, agreement with recent experiments can be demonstrated. The results require further interpretation, e.g., identification of physical mechanisms governing the reaction. Because of the semiclassical nature of atomic motion one would like to understand reactions as a result of a number of simple processes such as atoms moving along nearly classical trajectories or being trapped in resonance states. 

3) Where do you see this work developing in the future? 

For the first time, we have a tool for an accurate semiclassical analysis of angular scattering, which can be systematically applied to analyse the chemical kinetics of systems of practical interest and predict novel features and phenomena. 

4) Are there any particular challenges facing future research in this area? 

Further improvements are awaited in the accuracy of our computer codes and of potential energy surfaces, as well as further development of semiclassical techniques and of complex angular momentum analysis, in order to cope with the ample phenomenology emerging from both the calculations and the experiments.