Pressure studies of subthreshold photoionization: CH3I, C2H5I and C6H6 perturbed by Ar and SF6 Original Research Article

Subthreshold photoionization spectra of CH3I doped into Ar and SF6, and C2H5I and C6H6 doped into SF6, are reported for variations in both the dopant number density ρD and perturber number density ρP. The ρD and ρP 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 ρD and ρP 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 CH3I, the variations in the effective rate constants are discussed in terms of ground-state dopant and perturber properties.