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Resonant Auger transitions from the 3d −1 5p photoexcited states in Kr to the 4s −1 4p −1 5p and 4s −2 5p levels and subsequent Auger decay to the 4p 4 and 4s4p 5 states of Kr 2+ are studied by means of angle-resolved electron spectroscopy. The angular anisotropy parameters β are determined for most of the prominent lines in the spectrum of emitted electrons. It is found that the first-step spectator transitions are strongly anisotropic, while the secondstep participator transitions are almost isotropic. Extensive multiconfiguration Dirac-Fock calculations are performed which include correlations in all of the states involved. Noticeable improvements are achieved in comparison with early calculations. The energy position of the main spectral lines and their intensities are described satisfactorily. It turns out that the interference effects due to coherent excitation of resonances influence the anisotropy of the Auger emission significantly. The calculated β parameters agree very well with the experiment.

Molecular wave-packet (WP) interferometry has been demonstrated in the A electronic state of the HgAr van der Waals complex with two time-delayed UV fs pulses at 254 nm. The interferograms of three vibrational levels in the WP's display almost 100% fringe contrast as a function of the interpulse delay tau, which is tuned with sub-10 as stability and resolution. It is clearly observed that the three interferograms show their dephasing and rephasing within a single vibrational period, allowing us to prepare arbitrary relative populations of the three levels by adjusting a single parameter tau.