Lay summary
In the last years a tremendous progress has been made in understandingcombustion processes on the basis of chemical reactions, kinetics andthermodynamics. Still many highly important processes and elementaryreactions remain poorly understood. It is a challenge to reveal thedynamic aspects of chemical reaction paths. The aim of this project is theapplication of nonlinear ultrafast spectroscopy to unveil the 'real' timedynamics of combustion relevant molecules.
For this reason we proposed to extend variants of the nonlinearfemtosecond spectroscopic methods into the ultraviolet frequency range.Especially in the combustion research field where many species absorb inthe UV, the amount of possibly investigated species will be enlarged.Hence a successful application of the proposed 'two time delayed UV-fsCARS' method would provide a new tool for investigations in thefuture.
In this project, the importance of molecular dynamics should be linked totwo, in detail yet unsolved combustion relevant questions:

First, formaldehyde often appears as intermediate in combustion relevantreaction mechanisms and therefore plays a major role in the combustionprocess. We aim to investigate the dissociation dynamics of formaldehyde.Though formaldehyde has some model character (due to its well knownspectroscopy), it still provides interesting and unknown dynamicsconcerning its uni-molecular dissociation after photo excitation. Thevarious dissociation channels of the molecule (‘molecular’ and ‘radical’)compete with each other, and additional information about possible fasttunnel rates is expected to be obtained from the applied ultrafastspectroscopic methods.

Second, the origin of the soot production is still not fully understoodand of major importance to combustion research. In this context theinvestigations should be extended to larger molecules such as e.g1,5-hexadiyne. Femtosecond spectroscopy is proposed to be applied tofollow the fast nuclear rearrangements of C6H6 species preliminary to theformation of the first benzene ring. Hereby the main focus is on the fastreaction path of the propargyl ‘self-reaction’. This ring closure pathincludes several intermediates, which are the target of our interest. Thegoal is to monitor some of the fast nuclear rearrangements involved inthis process in real time.