Ionization of highly excited (Rydberg) atoms and attachment of ultraslow electrons to the SF6 molecule

The rate constants for collisional quenching by SF6 molecules of the Rydberg (nP series) states of sodium with principal quantum numbers n=23-40 are measured on selective three-step laser excitation in the atomic beam. It is shown that the main contribution to the quenching is from ionization involving the formation of an ion pair. It is found that the rate constant of the process is independent of n and is K-bar=(4.4±0.2)x10-7 cm3/s. The result accords with the data for the Rb ns- and nd-series and the Xe nf-series with other orbital momenta and confirms the validity of the quasiclassical description of the electron motion. A critical analysis of the data on the rate constants for slow electron attachment obtained by direct methods yields K≤(2.6±0.4)x10-7 cm3/s. The possible causes of the discrepancy between the values for the rate constant for electron attachment obtained by different methods are discussed