The CO⁺(A ²Π) RA electron spectra of CO*

Figure 4. The CO⁺(A ²Π) RA electron spectra of CO*. Upper panel: results are shown for Gaussian-shaped pulses of 4 fs duration, carrier frequency of 534.2 eV (i.e. the excitation of the O(1s⁻¹π*, v_r = 5) resonance) and different peak intensities computed employing the full formalism (Total) within the two models: no-DICES (dashed curves) and DICES (solid curves). The peak intensities chosen for the calculations (indicated near each spectrum) are those marked by the vertical dotted lines in figure 2. The electron energies corresponding to the energy positions of the v' vibrational levels of the CO⁺(A ²Π) state are marked by vertical dotted lines. Lower panel: weak-field RA electron spectra. Open circles: experiment [50]; dashed–dotted curve: the experiment [50] convolved with an apparatus function of 135 meV FWHM, which corresponds to a τ = 4 fs pulse; solid squares: calculations performed with a τ = 15 fs pulse, which corresponds to the experimental resolution in [50]. The no-DICES (dashed curves) and DICES (solid curves) calculations for a 4 fs pulse are nearly indistinguishable for weak fields.

Abstract

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*.