Dissociative attachment in e--H2collisions

Abstract

A study is made of the dissociative attachment of slow electrons on rovibrational levels of the hydrogen and deuterium molecules close to its energetic threshold. The electron-molecule interaction is described with an effective range approximation, similar to a previous work on the HCl molecule by Teillet-Billy and Gauyacq. The parameters required by this description were extracted from ab initio data on the fixed- R e^--H₂ system by Gibson and Morrison (1984) and McCurdy and Mowrey (1982), a unique parameter being adjusted on the experimental data. Although a resonance H₂^- state could be defined, the present work does not introduce it as an intermediate of the process; the electron is captured directly via non-adiabatic coupling into a negative energy state. The increase of the dissociative attachment cross section with the internal energy of the molecule is well represented, in particular the difference between the vibrational and rotational enhancements is accounted for. The results are discussed and compared with the experimental data of Schulz and Asundi (1967) and Allan and Wong (1978).