Three-periodic nets and tilings: natural tilings for nets

Rules for determining a unique natural tiling that carries a given three-periodic net as its 1-skeleton are presented and justified. A computer implementation of the rules and their application to tilings for zeolite nets and for the nets of the RCSR database are described

Novel Collective Autoionization Process Observed in Electron Spectra of He Clusters

The ionization dynamics of He nanodroplets irradiated with intense femtosecond extreme ultraviolet pulses of up to 10^13\u2009\u2009W/cm2 power density have been investigated by photoelectron spectroscopy. Helium droplets were resonantly excited to atomiclike 2p states with a photon energy of 21.4 eV, below the ionization potential (Ip), and directly into the ionization continuum with 42.8 eV photons. While electron emission following direct ionization above Ip is well explained within a model based on a sequence of direct electron emission events, the resonant excitation provides evidence of a new, collective ionization mechanism involving many excited atomiclike 2p states. With increasing power density the direct photoline due to an interatomic Coulombic decay disappears. It indicates that ionization occurs due to energy exchange between at least three excited atoms proceeding on a femtosecond time scale. In agreement with recent theoretical work the novel ionization process is very efficient and it is expected to be important for many other systems

A velocity map imaging apparatus for gas phase studies at FERMI@Elettra

22The design and evaluation of a velocity map imaging spectrometer specifically optimised for experiments at the FERMI free electron laser source are described. Optimisation of the set-up for the detection of high energy electrons (experimentally calibrated up to 45 eV), reduction of scattered light and characterisation of the pulsed gas source are outlined. The instrument has been tested using synchrotron light at the GasPhase beamline at Elettra, the Italian synchrotron source, and the results are presented. © 2011 Elsevier B.V. All rights reserved.nonenoneP. O'Keeffe;V. Feyer;P. Bolognesi;M. Coreno;C. Callegari;G. Cautero;A. Moise;K. Prince;R. Richter;R. Sergo;M. Alagia;M. D. Simone;A. Kivimäki;M. Devetta;T. Mazza;P. Piseri;V. Lyamayev;R. Katzy;F. Stienkemeier;Y. Ovcharenko;T. Möller;L. AvaldiP., O'Keeffe; V., Feyer; P., Bolognesi; M., Coreno; C., Callegari; Cautero, Giuseppe; A., Moise; K., Prince; R., Richter; R., Sergo; M., Alagia; M. D., Simone; A., Kivimäki; M., Devetta; T., Mazza; P., Piseri; V., Lyamayev; R., Katzy; F., Stienkemeier; Y., Ovcharenko; T., Möller; L., Avald

A modular end-station for atomic, molecular, and cluster science at the low density matter beamline of FERMI@Elettra

The low density matter end-station at the new seeded free electron laser FERMI@Elettra is a versatile instrument for the study of atoms, molecules and clusters by means of electron and ion spectroscopies. Beams of atoms, molecules and helium droplets as well as clusters of atoms, molecules and metals can be produced by three different pulsed valves. The atomic and molecular beams may be seeded, and the clusters and droplets may be pure, or doped with other atoms and molecules. The electrons and ions produced by the ionization and fragmentation of the samples by the intense light of FERMI can be analysed by the available spectrometers, to give mass spectra and energy as well as angular distributions of charged particles. The design of the detector allows simultaneous detection of electrons and ions using velocity map imaging and time-of-flight techniques respectively. The instruments have a high energy / mass resolution and large solid-angle collection efficiency. We describe the current status of the apparatus and illustrate the potential for future experiments

Commissioning and Initial Operation of FERMI@Elettra

This article describes the design goals of FERMI@Elettra, reports on the goals achieved so far and shows how the facility development has been driven by the new research frontier of ultra-fast, extreme ultra-violet and soft X-ray science. The commissioning phases and first experience with user pilot experiments are presented and discussed