We report on the status of a users’ end-station, MAC: a Multipurpose station for Atomic, molecular and optical sciences and Coherent diffractive imaging, designed for studies of structure and dynamics of matter in the femtosecond time-domain. MAC is located in the E1 experimental hall on the high harmonic generation (HHG) beamline of the ELI Beamlines facility. The extreme ultraviolet beam from the HHG beamline can be used at the MAC end-station together with a synchronized pump beam (which will cover the NIR/Vis/UV or THz range) for time-resolved experiments on different samples. Sample delivery systems at the MAC end-station include a molecular beam, a source for pure or doped clusters, ultrathin cylindrical or flat liquid jets, and focused beams of substrate-free nanoparticles produced by an electrospray or a gas dynamic virtual nozzle combined with an aerodynamic lens stack. We further present the available detectors: electron/ion time-of-flight and velocity map imaging spectrometers and an X-ray camera, and discuss future upgrades: a magnetic bottle electron spectrometer, production of doped nanodroplets and the planned developments of beam capabilities at the MAC end-station.

We have investigated the possibility to track and control correlation dynamics of valence electrons in krypton (Kr) initiated by the absorption of one XUV photon. In this investigation, pump-probe experiments have been performed where monochromatized single harmonics at photon energies 29.6, 32.8, and 35.9 eV have been used as pump to populate different intermediate excited states. A temporally delayed NIR pulse probes the population of various decay channels via the detection of Kr2+ ion yields and its transient profiles. We observe that by varying the NIR pulse intensity within a range from 0.3×1013 to 2.6×1013 W/cm2, the shape of the Kr2+ transient profile changes significantly. We show that by varying the intensity of the NIR pulse, it is possible - (i) to control the ratio between sequential and non-sequential double ionization of Kr; (ii) to selectively probe quantum beat oscillations between Kr+∗ satellite states that are coherently excited within the bandwidth of the XUV pulse; and (iii) to specifically probe the relaxation dynamics of doubly excited (Kr∗∗) decay channels. Our studies show that the contribution of different ionization and decay channels (i)-(iii) can be altered by the NIR pulse intensity, thus demonstrating an efficient way to control the ionization dynamics in rare gas atoms.

No abstract

In this paper, the authors present the characterization experiments of a 20 fs vacuum ultraviolet beam from a high harmonic generation source. The beam hits a silicon sample and passes a triple reflection gold polarizer located inside an ultrahigh vacuum chamber. The polarizer's Malus curve was obtained; the total acquisition time for each point of the curve was 30 s. This aims to be the first vacuum ultraviolet time-resolved user station dedicated to ellipsometry. The high harmonic beam is generated by a 12 mJ, 1 kHz, 20 fs, in-house-developed laser and detected by a back-illuminated charge-coupled device.