Observation and theoretical description of periodic geometric rearrangement in electronically excited nonstoichiometric sodium-fluoride clusters

We present two-color fs pump-probe spectra of Na2F which were recorded by employing excitation wavelengths around 1208 nm (pump) and ionization wavelengths around 405 nm (probe). The observed oscillatory structure of the signal with a period of 185 fs shows an excellent agreement with our simulated spectra. The employed ab initio Wigner distribution approach provides clear evidence that this observation is caused by photoinduced metal bond breaking followed by a butterfly-type periodic geometric rearrangement.     

Smectic membranes in motion: approaching the fast limits of x-ray photon correlation spectroscopy

The dynamics of the layer-displacement fluctuations in smectic membranes have been studied by x-ray photon correlation spectroscopy (XPCS). We report transitions from an oscillatory damping regime to simple exponential decay of the fluctuations, both as a function of membrane thickness and upon changing from specular to off-specular scattering. This behavior is in agreement with recent theories. Employing avalanche photodiode detectors and the uniform filling mode of the synchrotron storage ring, the fast limits of XPCS have been explored down to 50 ns.     

Size-fractionated characterization and quantification of nanoparticle release rates from a consumer spray product containing engineered nanoparticles

This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles (ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized environment. Time dependence of the particle size distribution in a size range of 10–500 nm and ENP release rates were studied using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size-calibrated electrostatic TEM sampler. The deposited particles were investigated using electron microscopy techniques in combination with image processing software. This approach enables the chemical and morphological characterization as well as quantification of released nanoparticles from a spray product. The differentiation of solid ENP from the released nano-sized droplets was achieved by applying a thermo-desorbing unit. After optimization, the setup was applied to investigate different spray situations using both pump and gas propellant spray dispensers for a commercially available water-based nano-silver spray. The pump spray situation showed no measurable nanoparticle release, whereas in the case of the gas spray, a significant release was observed. From the results it can be assumed that the homogeneously distributed ENP from the original dispersion grow in size and change morphology during and after the spray process but still exist as nanometer particles of size <100 nm. Furthermore, it seems that the release of ENP correlates with the generated aerosol droplet size distribution produced by the spray vessel type used. This is the first study presenting results concerning the release of ENP from spray products.     

Bethe Ansatz and the Spectral Theory of Affine Lie Algebra-Valued Connections I. The simply-laced Case

We study the ODE/IM correspondence for ODE associated to \({\widehat{\mathfrak{g}}}\)-valued connections, for a simply-laced Lie algebra \({\mathfrak{g}}\). We prove that subdominant solutions to the ODE defined in different fundamental representations satisfy a set of quadratic equations called \({\Psi}\)-system. This allows us to show that the generalized spectral determinants satisfy the Bethe Ansatz equations.     

Triple coincidence experiment to explore the two-electron continuum states of the projectile resulting from mutual ionization in 100-keV He0 + He collisions

The existence of the two-electron cusp in atomic collisions, i.e., the enhanced emission of two electrons in the forward direction with velocities equal to that of the projectile, has been investigated experimentally. Using a time-of-flight technique, the energies of the two electrons resulting from the simultaneous target and projectile ionization in 100-keV He(0)+He collisions have been measured by detecting triple coincidence between the electrons and the outgoing He(+) ion. The coincidence yield clearly shows a peak as a function of the electron energies at the expected cusp position. Furthermore, a strong correlation was found between the energies of the two electrons, which is traced back to an angular correlation of 180 degrees in the projectile-centered reference system.