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Dissociative electron attachment in effusive beams of has been studied in the incident electron energy range 0 - 11 eV. Two processes are observed at 2.4 and around 4.55 eV. From the ion kinetic energy and angular distributions, the symmetries of the dissociative resonant states have been determined as and . In the sulphur vapour formation occurs at zero energy and around 4 and 7.5 eV, in addition to the processes.

Ion yield spectra and angular distributions of Cl- and I- ions formed by dissociative electron attachment on ICl molecules have been obtained with a crossed-beam electron impact spectrometer, in the 0-6 eV energy range. Kinetic energy and angular measurements show that two ICl- states with 2 Pi 3/2 and 2 Pi 1/2 symmetry are involved in Cl- ion formation, one around 0.85 eV, associated with 2P3/2 neutral fragments, and the other around 4.55 eV (+I 2P1/2) respectively, whereas a 2 Sigma + and a 2 Pi resonance state are responsible for the I- (+Cl2P) ion formation around 1.45 and 3.7 eV respectively. The Cl- and I- relative differential cross sections do not show evidence of non-adiabatic dissociation processes. The analysis of the measured angular distributions also does not show any effect of the spin-orbit interaction upon the symmetry of the resonances, since they are found to have a pure Lambda -type symmetry.

Resume On utilise deux systemes d'echantillonnage differents pour l'etude de la discrimination en masse d'ions extraits d'un tube de derive; avec l'un de ces systemes, on realise un ecoulement visqueux; avec l'autre un ecoulement moleculaire. Dans le cas d'un ecoulement visqueux, on montre qu'au voisinage de l'orifice il y a competition entre l'ecoulement des ions dans le flux gazeux et le deplacement des ions dans le champ electrique. On n'observe pas de discrimination en masse dans l'analyse des ions O−, O2− et O3− resultant de l'attachement electronique dissociatif sur l'oxygene.

Dissociative electron attachment on an effusive beam of Na 2 is studied in the energy range 0–10 eV. A single Na − process is observed at a peak energy of 0.05 ± 0.05 eV. The attachment seems to concern mainly rovibrationally excited Na 2 . An absolute energy-integrated cross section of (3.6 ± 1.8) × 10 −18 cm 2 eV is determined by comparison with the known Na positive-ionization cross section.

The resonant state CO-(Cls) -1 (2pπ) 2 . first reported by King has been observed to decay by multiple Auger effect in all the positive-ionization channels of CO. The relative abundances for the resonant formation of CO + . CO 2+ . C + . O + , C 2+ ions have been measured. the decay to neutral states by normal Auger transitions is observed in the (O- + C + ion-pair formation.

Br- formation in HgBr2 has been studied by means of two cross-beam electron impact spectrometers, one equipped with a trochoidal electron monochromator and a magnetic mass analyser and the other one equipped with two 127 degrees electrostatic energy filters and a quadrupole mass analyser. It is found that the Br- cross section in the energy range 0-7 eV exhibits two peaks, at zero energy and 4.15 eV respectively. The energy distributions of Br- ions are obtained in the energy range of the second process, different interpretations are discussed.