Isotope effects of the collinear reactions F + HBr, F + DBr and F + MuBr

Abstract

The collinear reaction F + HBr, F + DBr and F + MuBr yield three dynamical effects which are characteristic for exoergic hydrogen transfer reactions: (a) strong population inversion of vibrational product distributions due to approximate conservation of translational energy (Baer′s rule); (b) oscillatory reactivity, i.e. reaction probabilities oscillate smoothly versus collision energy; (c) a spectrum of sharp resonances superimposed on effect (b), i.e. extraordinary variations of reaction probabilities at specific resonance energies E_r and within specific resonance widths Γ_r. These effects are influenced by isotopic substitutions of the light atom, which is transferred between its heavy partners. As a general trend, the effects are supported by decreasing masses, from D via H to Mu. Detailed results are derived from exact quantum state-to-state reaction probabilities which are evaluated with the help of S-matrix propagations along the systems' hyperspherical radial coordinates, and they are interpreted with the help of an extended version of the diagonal corrected vibrationally adiabatic hyperspherical (DIVAH) method.