State-selective dissociative double ionization of CH₃I and CH₂I₂ via I 4d core-hole states studied by multi-electron-ion coincidence spectroscopy

The dissociative double ionization of CH₃I and CH₂I₂ irradiated with extreme ultraviolet light at hv = 100 eV is investigated by multi-electron-ion coincidence spectroscopy using a magnetic bottle type electron spectrometer. The spin-orbit state-resolved Auger electron spectra for the I 4d core-hole states, (I 4d_3/2)⁻¹ and (I 4d_5/2)⁻¹, provide clear identifications of electronic states of CH₃I²⁺ and CH₂I₂²⁺. The dominant ion species produced after the double ionization correlate with the Auger electron energy, showing that different fragmentation pathways are open depending on the electronic states populated by the Auger decay. Theoretical calculations are performed to understand the fragmentation from the doubly charged states and the observed spin-orbit specificity in the Auger decay.