The H plus n-C5H12/n-C6H14 -> H-2(v('),j('))+C5H11/C6H13 reactions: State-to-state dynamics and models of energy disposal

The rovibrational state distributions for the H-2 product of the H + n-C5H1 2/n-C6H14-->H-2 + C5H11/C6H13 reactions at 1.6 eV collision energy are repo rted. The results are compared to measurements made on the kinematically an d energetically similar H + RH -->H-2 + R (RH = CH4, C2H6, and C3H8) reacti ons as well as the atom-diatom reactions H + HX -->H-2 + X(HX = HCl, HBr). For the title reactions, as for all the comparison reactions, the product a ppears in few of the energetically accessible states. This is interpreted a s the result of a kinematic constraint on the product translational energy. Characteristic of the H + RH reactions we have previously studied, the tit le reactions show increasing rotational excitation of the H-2 product with increasing vibrational excitation of it, a correlation that gets stronger a s the size of the alkane increases. Trends and variations in the product en ergy disposal are analyzed and explained by a localized reaction model. Thi s model predicates a truncation of the opacity function due to competing re active sites in the polyatomic alkane reactant, and a relaxation of the oth erwise tight coupling of energy and angular momentum conservation, because the polyatomic alkyl radical product is a sink for angular momentum. (C) 20 01 American Institute of Physics.