Reactive scattering of a supersonic oxygen atom beam : O + H₂S

Abstract

Reactive scattering of O atoms with H₂S molecules has been studied at an initial translational energy E≅30 kJ mol^-1 using a supersonic beam of O atoms seeded in He. Reactive scattering of HSO radicals is nearly isotropic but slightly favours the backward hemisphere with a product translational energy E′_av∼26 kJ mol^-1. The total reaction cross section was measured as a function of initial translational energy by using a He/Ne buffer gas mixture to vary the O atom velocity. The threshold energy E ₀ = 14 ± 2 kJ mol^-1 for the formation of HSO product is in good agreement with the activation energy for the overall reaction of O atoms with H₂S molecules. Hence the formation of HSO product represents an important primary pathway for the O + H₂S reaction which is initiated by bonding of the electrophilic O atom to the lone pair electrons of the S atom. The potential energy surface for H atom displacement has a barrier in the exit valley which promotes nearly isotropic scattering and high product translational energy. The heat of formation of the HSO radical is estimated as ΔH _f(HSO) = -6 ± 8 kJ mol^-1.