Multielectron dissociative ionization ofO2in an intense picosecond laser field

The multielectron dissociative ionization of ${\mathrm{O}}_2$ has been studied using an intense picosecond laser at 610 and 305 nm in the ${10}^{13}$–${10}^{15}$ W/${\mathrm{cm}}^2$ laser intensity range. The excitation mechanisms producing multicharged dissociating molecular ions are determined from the kinetic energies and laser-intensity dependences of the atomic oxygen ions following the fragmentation of the molecule. Both at 305 and 610 nm, the multicharged atomic fragments (${\mathrm{O}}^{+}$,${\mathrm{O}}^{2+}$,${\mathrm{O}}^{3+}$,${\mathrm{O}}^{4+}$) are produced from parent molecular ions that are sequentially ionized as they dissociate. Moreover, the transitions occur at well-defined internuclear distances independent of the peak laser intensity. A comparison with previous results obtained on ${\mathrm{N}}_2$ and CO is discussed.