Toward a quantitative analysis of the temperature dependence of electron attachment to SF 6 .

New flowing afterglow/Langmuir probe investigations of electronic attachment to SF ₆ are described. Thermal attachment rate constants are found to increase from 1.5 × 10 ^-7 cm ³ s ^-1 at 200 K to 2.3 × 10 ^-7 cm ³ s ^-1 at 300 K. Attachment rate constants over the range of 200-700 K (from the present work and the literature), together with earlier measurements of attachment cross sections, are analyzed with respect to electronic and nuclear contributions. The latter suggest that only a small nuclear barrier (of the order of 20 meV) on the way from SF ₆ to SF ₆ ^- has to be overcome. The analysis shows that not only s-waves but also higher partial waves have to be taken into account. Likewise, finite-size effects of the neutral target contribute in a non-negligible manner.