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

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 H2F complex (A(H) = 50.8, A(F) = 1.85, A(H) less than or equal to 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) less than or equal to 0.1 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, omega(0) similar to 3 x 10(10) s(-1)).