Abstract
The pressure effects on the charge yield and ion nucleation induced by resonance enhanced multiphoton ionization (REMPI) in a diffusion cloud chamber have been investigated. The ion nucleation spectrum is similar to the charge spectrum produced by the chromophore ion, thus providing further evidence for the identity of the nucleating ions. The measured charge decreases as the carrier gas pressure increases. Models based on collisional quenching of the intermediate state and ion-electron collisional recombination have been used to interpret the observed pressure effects. (C) 1997 Elsevier Science B.V.