Electron attachment to the SF6 molecule

Abstract

Various models for transition between electron and nuclear subsystems are compared in the case of electron attachment to the SF6 molecule. Experimental data, including the cross section of electron attachment to this molecule as a function of the electron energy and vibrational temperature, the rate constants of this process in swarm experiments, and the rates of the chemionization process involving Rydberg atoms and the SF6 molecule, are collected and treated. Based on the data and on the resonant character of electron capture into an autodetachment ion state in accordance with the Breit–Wigner formula, we find that intersection of the molecule and negative ion electron terms proceeds above the potential well bottom of the molecule with the barrier height 0.05–0.1 eV, and the transition between these electron terms has both the tunnel and abovebarrier character. The limit of small electron energies e for the electron attachment cross section at room vibrational temperature takes place at e ≪ 2 meV, while in the range 2 meV ≪ e ≪ 80 meV, the cross section is inversely proportional to e. In considering the attachment process as a result of the interaction between the electron and vibrational degrees of freedom, we find the coupling factor f between them to be f = aT at low vibrational temperatures T with a ≈ 3 × 10−4 K−1. The coupling factor is independent of the temperature at T > 400 K.