Hydrogen-atom transfer reactions of ground-state atomic carbon

Bimolecular reactions of ground state atomic carbon, C(3P), with small, saturated H-X molecules are investigated in a crossed molecular beam configuration. C(3P) atoms are generated by laser ablation of graphite, and the diatomic reaction products are detected using laser induced fluorescence. From the resulting nascent product rovibrational distributions, insights into the gas-phase reaction dynamics are obtained.;First, the results of the endothermic reactions of C( 3P) with H2, HCL HBr, CH3OH and CH4 are described and discussed. Due to the endothermicity of these reactions (DeltaH = 6.80--22.8 kcal/mol), the technique of free ablation is used to generate a beam of atomic carbon with translational energies >60 kcal/mol. Product CH is detected in all reactions, demonstrating that translational energy can be used to enhance reactivity. Rovibrational distributions are similar, with CH produced predominantly in u = 0 and rotational energies ranging between 900--1100 cm--1. In addition, the CH spin-orbit and Lambda-doublet sublevels are equally populated. Comparisons to the CH internal state distributions obtained for the corresponding reactions of C(1D) with H 2 and HCl also show remarkable similarities. The combined experimental and theoretical evidence strongly suggests that an insertion pathway involving the participation of carbene intermediates may be the primary mechanism for these reactions of C(3P).;Investigations are continued with the experimental study of the exothermic reaction of carbon (3P) with CHCl3. Here, the translational energy of atomic carbon is varied by seeding in carrier gases to investigate the effects of collision energy, and to further elucidate the role of C(3P) insertion into saturated hydrocarbons. Product CCl is detected and nascent CCl internal energy distributions are obtained. CCl is determined to be highly rotationally excited (Trot = 1500--1800 K) and the first excited vibrational level is significantly populated. Excellent agreement is obtained between these results and statistical estimations based on prior calculations, indicating that the reaction proceeds via a long-lived insertion complex. This supports the conclusions drawn about the C(3P) with CH4 and CH3OH, for which the evidence also argued in favor of an insertion mechanism.