Formation of the HHF complex in the reaction of thermal fluorine atoms with hydrogen molecules in solid Ar

Abstract

The reaction of F atoms with H 2 in an Ar matrix was studied with EPR spectroscopy. F 2 photolysis produces two well-known doublets of the H atom trapped in different crystal sites. Heating gives rise to an EPR spectrum assigned to the H 2F complex ( A H = 50.8, A F = 1.85, A H ⩽ 0.15 mT), the formation of which is attributed to the reaction of diffusing thermal F t atoms with H 2. The shape and width of the spectrum of the complex changes drastically with temperature due to the transitions between two stable configurations: A ( a F = 3.2 mT, a H ⩽ 3.2 mT) and B ( a F = 0.5 mT, a H = 0.4 mT) with an Arrhenius-like dependence of rate ( E a = 80 cal/mol, ω 0 ∼ 3 × 10 10 s −1).