Nonsequential double ionization of small molecules induced by a femtosecond laser field - art. no. 023403

Nonsequential double ionization of several molecules such as N-2,CO2,C2H2, and C3H4 in strong laser fields has been unambiguously identified from the ion-yield measurements in comparison with a sequential ionization model in the 10(13)-10(15) W/cm(2) laser intensity range. This effect is observed ma inly using linearly polarized laser light. In circular polarization, nonseq uential double ionization might be present, for instance for the C2H2 molec ule, but with a much lower contribution than in linear polarization. The ex perimental method allows us to detect all the double-ionization decay chann els that are the molecular dication and the two-missing electron fragmentat ion channels. The validity of a single-ionization tunneling model developed for atoms has been extended to molecules, and a good agreement is observed in laser intensity ranges where single-ionization processes take place.