Study on resonance-enhanced multiphoton ionization (REMPI) of SO 2 in the range 365–405 nm

Abstract

The resonance-enhanced multiphoton ionization (REMPI) of SO 2 in the range 365–405 nm has been studied using mass-distinguished excitation spectra. Most of the resonance peaks for both parent ion SO 2 + and fragment ions SO +, S + and O + in the excitation spectra have been assigned to the transition SO 2( a ̃ 3 B 1) ← SO 2( X ̃ 1 A 1) . It has been reasonably assumed that SO 2(C̃ 1B 2), produced by the subsequent excitation of SO 2(ã 3B 1), plays a key role in generating the fragment ions. It seems that tragment ions come mainly from the photoionization of neutral fragments dissociated from SO 2(C̃ 1B 2) while the parent ion is formed directly by further photoionization of SO 2(C̃ 1B 2). That the resonance peaks of the parent ion appear generally narrower than those of fragment ions can also be explained by the known spectral properties of SO 2(C̃ 1B 2).