Ion-pair formation in the collision of high Rydberg argon atoms with SF6 and C6F6 and negative ion lifetimes

The ion-pair formation in collision between argon atoms in high Rydberg states (HR) with SF6 and C6F6 has been investigated. The absolute cross sections are inversely proportional to the Ar(HR) velocity and increase monotonically with increasing principal quantum number n. Measurements of the negative ion lifetimes against autodetachment are reported and are >20 μsec for SF6- and approx.1 and >20 μsec for C6F6-. The present data are reviewed in light of the theoretical predictions of ''free electron'' models and the results of free electron experiments