Reactive scattering of a supersonic fluorine-atom beam: F + C2H5I, C3H7I, (CH3)2CHI

Reactive scattering of F atoms with C 2 H 5 I, C 3 H 7 I and (CH 3 ) 2 CHI molecules has been studied at an initial translational energy E ≈ 38 kJ mol -1 using a supersonic beam of F atoms seeded in He buffer gas. Centre-of-mass angular distributions of IF scattering show peaking in the forward and backward directions, which is consistent with reaction via persistent F-I-C 2 H 5 , F-I-C 3 H 7 and F-I-CH(CH 3 ) 2 complexes with lifetimes greater than two rotational periods. The extended microcanonical theory indicates that the angular distribution of reactive scattering for F + C 2 H 5 I arises from a range of transition state configurations generated by internal rotation about the extended C-I bond. The reactive scattering for F + C 3 H 7 I arises from a wide range of transition-state configurations, with sharply peaked forward and backward scattering from extended configurations and mildly peaked scattering from more contracted configurations. However, the range of transition-state configurations is much more limited for F + (CH 3 ) 2 CHI. This distinction confirms the persistence of significant C-I bonding, which restricts the rotation of the IF and C 2 H 5 , C 3 H 7 or (CH 3 ) 2 CH fragments in these product transition states.