Molecular Ionization of Chloromethane in Strong Fields: Nearest Neighbor Gateway to Highly Charged Ions

The strong and ultrastrong field-molecule interaction is a complex, many-body process involving multiple ionization processes that evolve during an ultrafast laser pulse. We present ion yields and molecular fragment energies for the ionization of chloromethane (CH$_{3}$Cl) in a laser field with intensities spanning from 10$^{14}$ W/cm$^{2}$ to 10$^{17}$ W/cm$^{2}$. As the laser intensity increases, ionization of CH$_{3}$Cl is observed to pass from molecular tunnelling, to enhanced ionization, to an atomic-like response. The energy spectra of the ions show no dependence on the intensity and have their source in dissociative molecular ionization. A classical model of an aligned C-Cl ion is used to dynamically model the interaction. Following an initial molecular ionization process, our results show enhanced ionization is a driving influence in the formation of low charge states until ionization become atomic-like and involves tightly bound ion states whose ionization is unaffected by nearest neighbor ions of similar ion charge.