Non-dissociative and dissociative ionization of a CO$^{+}$ beam in intense ultrashort laser pulses

We have investigated the ionization of CO$^{+}$ beams in intense ultrashort laser pulses. With the recent upgrades to our coincidence three-dimensional momentum imaging method we are able to measure both non-dissociative and dissociative ionization of the molecular-ion beam targets. Using CO$^{+}$ as an example, we have found that non-dissociative ionization (leading to the metastable dication CO$^{2+})$ involves a direct transition, i.e. the molecule is ionized with little or no internuclear distance stretch. Dissociative ionization (C$^{+}$+O$^{+})$ occurs both directly and indirectly, stretching first and then ionizing. Our results show that the yield of dissociative ionization is higher than that of non-dissociative ionization and can be manipulated with the laser pulse duration by suppressing the indirect ionization path using ultrashort pulses ($\le $10 fs).