Dissociative ionization of gas-phase chloromethanes by intense fields of picosecond and attosecond duration

The morphological features are explored of dissociative ionization (DI) of tetra-, tri-, and di-chloromethane molecules induced by intense electric fields of picosecond and attosecond duration. Picosecond-long fields are generated using linearly polarized light pulses (532 nm wavelength, 10¹³ W cm^-2 intensity) from a neodymium-doped yttrium aluminum garnet laser whereas attosecond-long fields are obtained by means of a fast (∼50 MeV) beam of Si³⁺ ions from a tandem accelerator. The temporal and directional properties of the intense fields that the chloromethanes are immersed in influence the DI pattern. For all three chloromethanes, the DI patterns measured in light-induced and in ion-induced fields differ from each other, and from those obtained using 70-eV electrons. The ion-impact results are conspicuous by the copious quantities of highly charged fragments and large fluxes of H⁺ ions, belying recently expressed expectations that short-duration field-molecule interactions would result in little or no fragmentation.