Total ion yield after the exposure of CO to a coherent Gaussian-shaped pulse of duration 4 fs and carrier frequency of 534.2 eV (i.e
Figure 2. Total ion yield after the exposure of CO to a coherent Gaussian-shaped pulse of duration 4 fs and carrier frequency of 534.2 eV (i.e. the excitation of the O(1s−1π*, vr = 5) resonance). Upper panel: contributions of different physical mechanisms to the exact result (DICES). These include approximations involving contributions of only the resonant channel (Resonant), of only the direct ionization channel (Direct), of both the direct and resonant channels and the interference between them (Interference) and contributions of all mechanisms including the direct PI of the resonance (Total). Lower panel: calculations performed including all ionization mechanisms (i.e. without approximations (Total)) but for different models of the nuclear dynamics, i.e. the atomic-like model (Atomic), rotation-free model (no DICES) and the exact model accounting for the vibrational and rotational degrees of freedom (DICES). The vertical dotted lines indicate the peak intensities chosen for the calculation of the RA spectra in figure 4.
The dynamics of the resonant Auger (RA) decay of the core-excited CO*(1s−1π*) molecule in intense x-ray laser pulses is studied theoretically. The present approach includes the impact of the analogue of conical intersections of the complex potential energy surfaces of the ground and 'dressed' resonant states induced by intense x-ray pulses. It also takes into account the decay of the resonance and the direct photoionization of the ground state, both populating the same final ionic states coherently, as well as the direct photoionization of the resonance state itself. The individual impacts of these physical processes on the total ion yield, the CO+(A 2Π) electron spectrum and the ro-vibrational distributions of the neutral molecules remaining in the ground electronic state after the laser pulse has expired are analysed and compared to those reported previously for the C*O resonance. It is also demonstrated that the RA effect of molecules by strong laser pulses of resonant carrier frequency is an efficient process to produce two-site double-core-hole–one-particle states of CO*.