A Study on Multiphoton Ionization-Dissociation of OCS Molecule using Time-of-Flight Mass Spectrometry

Multiphoton ionization-dissociation process of OCS molecules is studied using time-of-flight mass spectrometer with apulsed ultraviolet laser. Four ion peaks assigned to OCS⁺, S’, CO⁺ and C⁺ are observed under 278.5nm（I¹Π-X¹Σ⁺ （000-000））, 280.0nm（F¹Π-X¹Σ⁺）) and 281.1nm laser irradiation with different laser power. According to the experimental results, the multiphoton ionization-dissociation machanism of OCS molecule at those wavelengths are proposed as follow: First, OCS molecule is ionized to generate OCS⁺ via （2+1） photon （two photon resonant excitation and one photon ionization） process at 278.5nm and 280.0nm as well as 3 photon nonresonant ionization process at 281.1nm respectively. Then, OCS⁺ can absorb one more photon and dissociate to produce S⁺ and CO. In addition, CO⁺ and C⁺ might be generated from multiphoton ionization-dissociation of CO molecules.