PRESSURE EFFECTS ON THE CHARGE YIELD AND ION NUCLEATION INDUCED BY RESONANCE-ENHANCED MULTIPHOTON IONIZATION

The pressure effects on the charge yield and ion nucleation induced by resonance enhanced multiphoton ionization (REMPI) in a diffusion clou d chamber have been investigated. The ion nucleation spectrum is simil ar to the charge spectrum produced by the chromophore ion, thus provid ing further evidence for the identity of the nucleating ions. The meas ured charge decreases as the carrier gas pressure increases. Models ba sed on collisional quenching of the intermediate state and ion-electro n collisional recombination have been used to interpret the observed p ressure effects. (C) 1997 Elsevier Science B.V.