Molecules in intense laser fields: Enhanced ionization in a one-dimensional model ofH2

A one-dimensional model of ${\mathrm{H}}_2$ is used to examine the nonlinear behavior of a pair of electrons in the presence of intense laser fields and fixed nuclei. We present ionization rates of ${\mathrm{H}}_2$ at different frequencies and intensities of short intense electromagnetic pulses by solving exactly the time-dependent Schrödinger equation for the above system as a function of internuclear distance. Anomalously high ionization rates are found at large critical internuclear separations, akin to similar results found previously in the one-electron molecule ${\mathit{H}}_2$ ${\mathrm{}}^{+}$. Independent one-electron and simultaneous two-electron ionizations are identified from the numerical simulations to occur at different intensities and frequencies. Field-induced barrier suppression models are shown to explain qualitatively the numerical results. © 1996 The American Physical Society.