Absolute cross sections have been measured for reactants typically found in carbon tetrafluoride (CF(4)) discharges for collision energies below a few hundred electron volts. The reactions investigated include collision-induced dissociation and dissociative electron transfer reactions for CF(+)(3) and F(+) colliding with CF(4), and collisional electron detachment for F(-) colliding with CF4. Also presented are measurements of energies and relative intensities of ions generated in dc Townsend CF4 discharges with E/N values ranging from 4 x 10(-18) V m(2) to 25 x 10(-18) V m(2) [4 to 25 kTd]. Ion energy and ion intensity data for the Townsend discharges are analyzed in light of the measured cross sections.

Integral and differential cross section measurements at low collision energies for the N 2 + + CH 4 / CD 4 reactions Measurements of total cross sections for collision induced dissociation, proton abstraction, and charge transfer have been made for collisions of CH 4 ϩ with CD 4 , H 2 , and Ar. The laboratory collision energies range from a few up to 400 eV, and isotopic substitutions have been made where possible to investigate any possible isotope effects, and for some reactants, to more closely identify the product ions. Cross sections for all reaction channels are observed to be small; Շ5 Å 2 for the methane target, Շ0.5 Å 2 for the hydrogen target, and Շ2 Å 2 for the argon target. For the methane and hydrogen targets, proton abstraction is observed at low energies while charge transfer occurs for energies տ10 eV. The implications of internal energy present in the CH 4 ϩ projectile for the cross section measurements is discussed. In addition, decomposition of CD 4 H ϩ is addressed in terms of recent calculations related to the structure of the CH 5 ϩ ion.

Insulating gas mixtures containing SF6 have been promoted to serve as replacements for pure SF6 in order to reduce SF6 atmospheric emission. It has been argued that some synergism may be achieved by choosing proper buffer gases in mixtures with SF6 such that the buffer gases efficiently slow down electrons into an energy range where the electron attachment cross section for SF6 is large. A complete understanding of the dielectric properties of SF6 mixtures obviously requires information about electron detachment from SF6" as collisional electron detachment may be the principal source of discharge initiation in SF6 mixtures. In this paper, we report total cross-section measurements for electron detachment and collision induced dissociation for collisions of SF6"with N2 for collision energies ranging up to a few hundred eV. The experimental results are analyzed using a two-step collision model where the unimolecular decomposition of collision ally excited SF6" ions is described in a statistical framework.