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In this work we present the results from two experiments dedicated to search for quadrupolecollective isovector valence-shell excitation, the states with so-called mixed proton-neutron symmetry (MSS), in nuclei around the doubly magic nucleus 208Pb. 212Po was studied in an α-transfer reaction. 204Hg was studied in an inverse kinematics Coulomb excitation reaction on a carbon target. Both experiments provide indications for existence of one-phonon MSSs. Those are the first experimentally identified MSSs in the mass A ≈ 208 region.

The one-quadrupole phonon excitation of mixed symmetry, the 2+1,ms state, is a fundamental building block of nuclear structure. This article gives a summary of our recent experimental research on this excitation mode in the A =90 and A =130 mass regions.

Electrically charged metallic microparticles and nanoparticles have been trapped under a free surface of superfluid 4He in a vertical static electric field. We report the details of the trapping technique and the observed dynamics of the trapped particles moving along the surface and driven by surface waves, by a static horizontal electric field, and by a thermal counterflow within the surface layer of liquid He. [ABSTRACT FROM AUTHOR]

The formation of high-mass stars is one of the major topics of astrophysical research, in particular the process of accretion from largescale clouds down to small-scale cores. We have selected the nearby, filamentary, high-mass star forming complex NGC6334 to study the gas velocity at different scales and probe the infall rates onto the protostellar cores embedded in the NGC6334-I and I(N) clusters. This study makes use of single-dish and interferometric submillimeter observations, complemented with 3D numerical non-LTE radiative transfer modeling. We measure a mass accretion rate of 10-5Mʘ yr-1 throughout the filament increasing up to 10-3Mʘ yr-1 towards the densest regions where high-mass stars are forming. At smaller scales, our 3D model is consistent with accretion rates of 10-3Mʘ yr-1 towards the clusters, and 10-4Mʘ yr-1 onto the protostars. [ABSTRACT FROM AUTHOR]

We present results from radiative transfer modeling of the continuum emission towards Sagittarius B2 (hereafter Sgr B2). We have developed a radiative transfer framework - Pandora - that employs RADMC-3D (Dullemond 2012) for a self-consistent determination of the dust temperature. With this pipeline, we have set-up a single model that consistently reproduces the thermal dust and freefree continuum emission of Sgr B2 spanning four orders of magnitude in spatial scales (0.02-45 pc) and two orders of magnitude in frequency (20-4000 GHz). [ABSTRACT FROM AUTHOR]

Present performance and future development of the free-electron lasers (FELs) in Hamburg--FLASH for the extreme ultraviolet and the European XFEL for the soft and hard x-ray regimes--are presented. As an illustration of the unprecedented characteristics of these sources a few recent examples of experiments performed in the area of atomic, molecular and optical (AMO) physics are described. The results highlight in particular the available high photon intensities, the short pulse durations and the coherence of the FEL beam. Nonlinear processes involving for the first time inner-shell electrons, time-resolved experiments on the few femtosecond timescales, and imaging experiments on small particles have been the focus of these studies, demonstrating the unique potential of short-wavelength FELs and pointing to numerous exciting future opportunities. [ABSTRACT FROM AUTHOR]

Electrically charged metallic micro- and nanoparticles are trapped under a free surface of superfluid He in a vertical static electric field. We observe a static deformation of the charged liquid surface in the form of a Taylor cone and the emission of a charged liquid helium jet (electrospray). Our numeric calculations reproduce the static shape of the cone. [ABSTRACT FROM AUTHOR]

Ultrafast extreme ultraviolet and X-ray free-electron lasers are set to revolutionize many domains such as bio-photonics and materials science, in a manner similar to optical lasers over the past two decades. Although their number will grow steadily over the coming decade, their complete characterization remains an elusive goal. This represents a significant barrier to their wider adoption and hence to the full realization of their potential in modern photon sciences. Although a great deal of progress has been made on temporal characterization and wavefront measurements at ultrahigh extreme ultraviolet and X-ray intensities, only few, if any progress on accurately measuring other key parameters such as the state of polarization has emerged. Here we show that by combining ultra-short extreme ultraviolet free electron laser pulses from FERMI with near-infrared laser pulses, we can accurately measure the polarization state of a free electron laser beam in an elegant, non-invasive and straightforward manner using circular dichroism.

Metal clusters serve as model systems to study basic problems of electronic correlation. Vacuum ultraviolet light from the free-electron laser FLASH ionizes 5d electrons from mass-separated negatively charged clusters, thus transiently leading to core-ionized neutral systems. Shielding of the core hole affects the electron binding energy. From the strong deviation from expectations of the metallic droplet and jellium models we conclude on reduced electronic shielding once the cluster size falls below about 20 atoms. This suggests a metal-to-nonmetal transition, in agreement with previous local density approximation calculations.