Dissociative ionization of H2+ using intense femtosecond XUV laser pulses

The dissociative ionization of H-2(+) interacting with intense, femtosecond extreme-ultraviolet laser pulses is investigated theoretically. This is done by numerical propagation of the time-dependent Schrodinger equation for a collinear one-dimensional model of H-2(+), with electronic and nuclear motion treated exactly within the limitations of the model. The joint energy spectra (JESs) are extracted for the fragmented electron and nuclei by means of the time-dependent surface flux method. The dynamic interference effect, which was first observed in one-electron atomic systems, is in the present work observed for H-2(+), emerging as interference patterns in the JESs. The photoelectron and the nuclear energy spectra are obtained by integration of the JESs. Without the JESs, the photoelectron spectrum itself is shown to be inadequate for the observation of the dynamic interference effect. The resulting JESs are analyzed in terms of two models. In one model the wave function is expanded in terms of the essential states of the system, consisting of the ground state and the continuum states, allowing for the interpretation of the main features in the JESs in terms of dynamic interference. In the second model the photoelectron spectra from fixed-nuclei calculations are used to reproduce some features of the JESs using simple reflection arguments. The range of validity of these models is discussed and it is shown that the consideration of the population of excited vibrational states is crucial for understanding the structures of the JESs.