Hydrogen abstraction reactions by atomic fluorine. V. Time‐independent nonthermal rate constants for the 18F+H2 and 18F+D2 reactions

Abstract

The general time‐independent collision theory formulation for the bimolecular rate constant has been adapted for the description of hot atom systems. Two types of hot atom energy distribution functions have been considered in an application to the ¹⁸F+H₂ reaction system: (i) a δ‐function distribution, and (ii) a steady‐state Maxwellian distribution characterized by a hot atom temperature T_A. From the time‐independent solution of the Boltzmann equation together with microscopic reactive cross sections determined from quasiclassical trajectory computations, nonthermal ¹⁸F+D₂ processes. The results showed little sensitivity to the assumed shape of the hot atom energy distribution or to the magnitude of the barrier height along the reaction coordinate. The intermolecular kinetic isotope effect κ_H2/κ_D2 provided a sensitive probe of the average energy of hot reaction, suggesting an average ¹⁸F laboratory kinetic energy of 50±10 eV for the ¹⁸F+H₂ process under nuclear recoil conditions.