DISSOCIATIVE RECOMBINATION AND DISSOCIATIVE EXCITATION OF (HEH-HE-4 -ABSOLUTE CROSS-SECTIONS AND MECHANISMS())

Absolute cross sections have been determined for the dissociative reco mbination and dissociative excitation of (HeH+)-He-4 electron energies below 30 eV. The dissociative recombination cross section is in semiq uantitative agreement with recent theoretical results by Sarpal, Tenny son, and Morgan [J. Phys. B 27, 5943 (1994)] and Guberman [Phys. Rev. A 49, R-1277 (1994); in XIXth International Conference on the Physics of Electronic and Atomic Collisions, Whistler, Canada, AIP Conf. Proc. No. 360, edited by L. J. Dube, J. B, A. Mitchell, J. W. McConkey, and C. E. Brion (AIP, New York, 1995), p. 307], The calculated resonant s tructure below a collision energy of 1 eV was not fully reproduced by the experiment, The quantum states of the dissociative recombination p roducts at 0 eV collision energy have been determined; ground-slate he lium and excited hydrogen atoms (n=2) are dominantly formed, in agreem ent with recent predictions by Guberman. The dissociative excitation h as an onset around 10 eV and follows the shape of the dissociative rec ombination cross section, illustrating that both processes start with the formation of doubly excited neutral slates that lie in the ionizat ion continuum as well as in the dissociation continuum. The dissociati ve excitation cross section is in quite good agreement with recent cal culations by Orel and Kulander.