Dissociation dynamics of positive-ion and negative-ion fragments of gaseous and condensed Si(CH3)2Cl2 via Si 2p, Cl 2p, and Cl 1s core-level excitations

Lu, K. T.; Chen, J. M.; Lee, J. M.; Chen, C. K.; Haw, S. C. Taiwan

The state-selective positive-ion and negative-ion dissociation pathways for gaseous and condensed Si(CH₃)₂Cl₂ following Cl 2p, Cl 1s, and Si 2p core-level excitations have been characterized. The excitations to a specific antibonding state (15a₁^* state) of gaseous Si(CH₃)₂Cl₂ at the Cl 2p, Cl 1s, and Si 2p edges lead to significant enhancement of fragmented ions. The ion enhancement at the specific core-excited states is closely correlated to the ion kinetic energy distribution. The results deduced from ion kinetic energy distribution are consistent with the molecular orbital calculations in Si(CH₃)₂Cl₂ using the ADF package. The Cl^- desorption yields for Si(CH₃)₂Cl₂/Si(100) at ~ 90 K are notably enhanced at the 15a₁^* resonance at both Cl 2p and Si 2p edges. The resonant enhancement of Cl^- yield occurs through the formation of highly excited states of the adsorbed molecules. These results provide an insight into the comprehensive understanding of the state-selective ionic fragmentation of molecules via core-level excitation.

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