The photoionization of methane is reported for intensities up to 10(19) W/cm2 with linear and circular polarized light. While fragmental ions (e.g., CH3+, CH+, C+, C2+) created from 10(14) W/cm2 to 10(15) W/cm2 are formed by Coulomb explosion, ionization to form C3+ and C4+ involves Coulomb explosion and tunneling ionization. In ultrastrong fields, removal of a carbon K-shell electron from methane proceeds via tunneling and rescattering ionization, without the influence of molecular channels. Photoelectrons from methane at 10(19) W/cm2 extend up to kinetic energies of 0.6 MeV.

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The dissociative recombination of H 3 + with electrons can have two exit channels, namely e + H 3 + -H + H + H (channel I), and e + H 3 + -H 2 + H (channel II). A new technique has been developed which has been used to determine the relative contributions of channels I and II to the overall recombination process. Over the energy range from 0.01 to 0.05 eV it has been found that channel I dominates.

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