Ultrafast proton migration and Coulomb explosion of methyl chloride in intense laser fields

Abstract

We investigated the ultrafast proton migration and the Coulomb explosion (CE) dynamics of methyl chloride (CH₃Cl) in intense femtosecond laser fields at the wavelengths of 800 nm (5.5 × 10¹⁴ W/cm²) and 400 nm (4 × 10¹⁴ W/cm²), respectively. Various fragment channels from molecular dication and trication were observed by coincidence momentum imaging through the measurement of their kinetic energy releases (KERs). The proton migration from different charged parent ions was analyzed from the obtained KER distributions. For the direct CE channel of CH₃⁺ + Cl⁺ and CH₃⁺ + Cl²⁺, the contribution of multiply excited electronic states and multicharged states is identified. In addition, the measurements of relative yields of the fragmentation channel at different laser wavelengths provide a selective control of proton migration for CH₃Cl molecules in intense laser fields.