Two-step Coulomb explosions of diatoms in intense laser fields

A two-step model of Coulomb explosions of diatoms in intense laser fields is presented. In this model the molecule loses several electrons when the atoms are at the equilibrium internuclear distance and then fast Coulomb explosions occur until the products reach a critical distance R(c) congruent to 9 Bohr, at which several additional electrons are lost due to a recently discovered maxima of ionization rates occurring at R = R(c). Then the subsequent Coulomb explosion for the higher-charged ions takes place. The total combined Coulomb explosion energy agrees well with experimental results, showing striking regularities. The origin and intensity dependence of unexpectedly high ionization rates of dissociating nuclei at preferential, large internuclear distances R = R(c) is also discussed and an analytic expression for R(c) is derived.