Revealing and controlling nuclear dynamics following inner-shell photoionization of N2

In this paper, we apply the Monte Carlo wave packet method to study the ultrafast nuclear dynamics following inner-shell photoionization of N2 exposed to an ultrashort intense x-ray pulse. The intermediate states in N2+ are highly excited so that autoionization takes place from these states to the quasibound or dissociative electronic states in N2++. The nuclear kinetic energy release (KER) spectra following double ionization of N2 are obtained by using the spectral methods. The very sharp peaks in the nuclear KER spectra, which were, however, absent from many relevant experiments due to a limited vibrational resolution, can be ascribed to the long-lived vibrational resonances supported by the quasibound states in N2++. The origins for the other main characteristic structures appearing in the nuclear KER spectra are also identified. To control the fragmentation dynamics of doubly ionized N2, the x-ray-pump-infrared-probe setting is employed. It is found that the laser-induced one-photon resonant transitions between the dissociative 11 pi g state and the quasibound 11 pi u state at around R = 3 a.u. are responsible for suppression or enhancement of the signals at different energy regions in the nuclear KER spectra. In addition, the delay-dependent nuclear KER distributions are constructed to achieve time-resolved imaging and controlling of the ultrafast nuclear dynamics that takes place following inner-shell photoionization of N2.