Isomer-resolved product detection

We use the synchrotron radiation at the Advanced Light Source (at the Lawrence Berkeley National Laboratory in Berkeley California to probe the products of elementary reactions between small free radicals (CH radicals, C atoms) and small oxygen and nitrogen containing molecules. The chemical reactions are initiated by pulsed laser photolysis and the reaction products are ionized by tunable vacuum ultraviolet which allows the detection of isomers of same mass but different ionization energy. The comparison of the experimental isomer distributions to quantum calculations provides fundamental information about the reaction mechanism. Detecting the isomers produced by reaction of C(3P) with small unsaturated hydrocarbons provides information about the molecular growth mechanisms in plasmas, combustion and interstellar chemistry.
                                                  Photoinization spectrum of the C + C3H6 reaction at 5 Torr and 360 K

Proposed mechanism for the reaction of ground state C(3P) atoms with butene isomers

The carbon atom is likely to add to the molecule instauration through cyclic addition followed by rapid isomerization of the adduct. The experimental data are consistent with either H-, CH3-, and –C2H5 elimination to form propargyl or substituted propargyl radicals. The isomeric structure of the final products depends on that of the butene reactant structure. 

The detection of resonance stabilized radicals from the C(3P) + butene isomers reactions suggests that their formation will be enhanced under plasma assisted combustion conditions considerably changing the molecular growth chemical scheme. The estimated branching ratios obtained in the present experiments are important data for the design of new combustion models under high-energy conditions such as those found in plasma.