Pressure studies of subthreshold photoionization: CH 3I, C 2H 5I and C 6H 6 perturbed by Ar and SF 6

Abstract

Subthreshold photoionization spectra of CH 3I doped into Ar and SF 6, and C 2H 5I and C 6H 6 doped into SF 6, are reported for variations in both the dopant number density ρ D and perturber number density ρ P. The ρ D and ρ P dependence of the subthreshold structure is discussed in terms of the excited state processes of electron attachment and associative ionization. The variation in the subthreshold photocurrent as a function of ρ D and ρ P leads to the determination of the effective rate constants for these processes. These constants are then analyzed with respect to the properties of the excited dopant Rydberg state. For CH 3I, the variations in the effective rate constants are discussed in terms of ground-state dopant and perturber properties.