The gas phase photoemission beamline at Elettra

Respiratory diseases are one of the greatest causes of morbidity and mortality in humans, affecting people at all stages of their lives. Indeed, respiratory failure is a major cause of morbidity and mortality in newborn infants, asthma is a common disease in children, and pulmonary fibrosis, emphysema, and asthma are all major health issues in adults [1 Scott, I.A. 2008. Chronic disease management: A primer for physicians. Intern Med J., 38(6): 427–37. [PubMed] , [Google Scholar]]. Our research at SPring-8 has mainly focused on the transition to air-breathing at birth, but has also focused on adult lung diseases such as pulmonary fibrosis and asthma, which has resulted from the application of new imaging developments.     

First observations of infrared synchrotron radiation at Elettra

Significant progress has been made in the last few years in short-bunch operation of third-generation synchrotron light sources, achieved by “lowα” optics for storage rings [1 Abo-Bakr, M. 2002. Phys. Rev. Lett., 88: 254801[Crossref], [PubMed] , [Google Scholar]–4 Müller, A.-S. Short-pulse operation of storage ring light sources. Proceedings of IPAC2013. Shanghai, China. (in press) [Google Scholar]]. The term α is a machine optics parameter describing the particle orbit length L as a function of the particle momentum p, L = L₀(1 + α(p ? p₀)/p₀), with respect to the nominal values indicated by the index “₀”. The “zero current” bunch length σ is then proportional to . Included here is the rf-voltage temporal gradient, V′ = dV/dt, which additionally influences the bunch length and will be required further. Thus, lowering α leads to a reduced bunch length all around the ring and radiation of the short bunches is supplied to all beamlines. These short bunches produce short X-ray pulses of equal length suitable for time-resolved measurements. Simultaneously, the short electron pulses emit intense, coherent THz radiation.     

Phase-Contrast Mammography at the SYRMEP Beamline of Elettra

At the SYnchrotron Radiation for MEdical Physics (SYRMEP) beamline of Elettra, a widespread research activity in bio-medical imaging has been developed since 1997 [1 Arfelli, F. 1998. Low-dose phase contrast X-ray medical imaging. Phys. Med. Biol, 43: 2845 [Google Scholar]]. The core program carried out by the SYRMEP research team concerns the use of synchrotron radiation (SR) for mammography in the effort of improving image diagnostic quality innovating the imaging technique and the detection system.     

Characterization of coherent THz radiation bursting regime at Elettra

Coherent Terahertz radiation has been observed in the third generation synchrotron light source Elettra. The radiation emitted in bursts shows a wavelength distribution shorter than the nominal electronic bunch length suggesting that the microscopic emission mechanism is due to the beam instabilities. In this paper we discuss the effects of the instabilities and present preliminary spectroscopic measurements.     

Meeting Report: Ten Years of Atomic and Molecular Science at Elettra

On the 31^st of May and the 1^st of June, 2007, a workshop to celebrate 10 years of atomic and molecular science was held at Elettra. The occasion marked the 10^th anniversary since the first beamtime was officially allocated to a user at the Gas Phase beamline, namely George King of Manchester University. As a satisfied user, King was not only present, but had beamtime during the workshop.     

Photoionization studies of the atmospherically important species N and OH at the Elettra synchrotron radiation source

In this paper angularly resolved photoelectron spectra (PES) and constant-ionic-state (CIS) spectra are presented for the atmospherically important species N and OH.The natural width Γ, line shape parameters q and ρ² and discrete oscillator strengths f have been measured for the members of the N*[2s2p³(⁵S), np] (⁴P) ← N(⁴S) autoionizing resonances for n = 5–10. The n = 5 parameters calculated in this work are in good agreement with the values obtained previously whereas for the resonances with n = 6–10 the values of these parameters are reported for the first time. The asymmetry parameter (β) for the first band of N atoms, the N⁺(³P) ← N(⁴S) ionization, has also been measured in the photon energy range of the above autoionizing resonances.For OH, CIS spectra have been recorded for the first photoelectron band corresponding to the ionization OH⁺(X³Σ⁻, v⁺ = 0) ← OH(X²Π, v″ = 0). In these spectra, rotationally partially resolved bands associated with OH*(a¹Δ3d, v′ = 0) ← OH(X²Π, v″ = 0) resonances have been observed. Suggestions for their assignment are made on the basis of their positions and band simulations which use rotational line strength calculations.     

Completion of the first phase of development of the European UV/VUV free-electron laser at Elettra

The Swiss Light Source, located at the Paul Scherrer Institut, is a third-generation synchrotron light source characterized by its exceptional stability and continuous top-up mode of operation. With a storage ring energy of 2.4 GeV, it provides photon beams of high brightness for research in materials science, biology and chemistry.     

Photoelectron spectroscopy of atomic oxygen using the Elettra synchrotron source

Atomic oxygen has been studied using angle resolved photoelectron spectroscopy (PES) and constant-ionic-state (CIS) measurements using radiation from the Elettra synchrotron as the photon source. Relative partial photoionization cross-sections and angular distributions for the O⁺(⁴S) ← O(³P) and O⁺(²D) ← O(³P) ionizations have been measured as a function of photon energy from threshold (13.6 eV) to 19.0 eV. Comparison of the results obtained with recent experimental work performed at lower resolution reveals a number of differences and comparison with results of recent calculations shows the need for the inclusion of coupling intermediate between the j-j and L-S limits in future calculations of photoionization cross-sections and angular distributions. This work has demonstrated the feasibility of and results to be expected from angle resolved PES and CIS measurements on reactive intermediates at Elettra, a third-generation synchrotron source, and further studies on small molecular radicals are proposed.     

New optical methods to study director orientation in liquid crystals

Summary We report new optical methods useful to investigate the orientational order of nematic liquid crystals. The first one uses a linear optical technique and a variable-thickness cell to get a precise measurement of the anchoring energies at the boundaries. The second one exploits the nonlinear self-phase modulation to evaluate the elastic anisotropy of a nematic liquid crystal. Examples are reported of measurements performed on hybrid aligned liquid crystals. Also with GNSM and CISM, Unità di Cosenza.     

Current status of the TwinMic beamline at Elettra: a soft X‐ray transmission and emission microscopy station

The current status of the TwinMic beamline at Elettra synchrotron light source, that hosts the European twin X‐ray microscopy station, is reported. The X‐ray source, provided by a short hybrid undulator with source size and divergence intermediate between bending magnets and conventional undulators, is energy‐tailored using a collimated plane‐grating monochromator. The TwinMic spectromicroscopy experimental station combines scanning and full‐field imaging in a single instrument, with contrast modes such as absorption, differential phase, interference and darkfield. The implementation of coherent diffractive imaging modalities and ptychography is ongoing. Typically, scanning transmission X‐ray microscopy images are simultaneously collected in transmission and differential phase contrast and can be complemented by chemical and elemental analysis using across‐absorption‐edge imaging, X‐ray absorption near‐edge structure or low‐energy X‐ray fluorescence. The lateral resolutions depend on the particular imaging and contrast mode chosen. The TwinMic range of applications covers diverse research fields such as biology, biochemistry, medicine, pharmacology, environment, geochemistry, food, agriculture and materials science. They will be illustrated in the paper with representative results.     

Angle‐resolved photoemission spectroscopy and imaging with a submicrometre probe at the SPECTROMICROSCOPY‐3.2L beamline of Elettra

The extensive upgrade of the experimental end‐station of the SPECTROMICROSCOPY‐3.2L beamline at Elettra synchrotron light source is reported. After the upgrade, angle‐resolved photoemission spectroscopy from a submicrometre spot and scanning microscopy images monitoring the photoelectron signal inside selected acquisition angle and energy windows can be performed. As a test case, angle‐resolved photoemission spectroscopy from single flakes of highly oriented pyrolitic graphite and imaging of the flakes with image contrast owing to rotation of the band dispersion of different flakes are presented.     

Temperature variations in the director orientation and anchoring energy at the surface of cholesteric layers

Slight changes with temperature in the director orientation at the surface of a perfect planar cholesteric liquid crystal (CLC) layer, which are precursors of a jump in the pitch of the cholesteric helix, are observed by measuring the temperature dependence of the optical transmission spectra of the layer. The observed changes in the director orientation are described in the framework of the continuum theory of CLCs, supplemented with allowance for the surface anchoring forces. In particular, the angle of deviation of the director at the surface from the alignment direction at the exact temperature of the jump in pitch is expressed in terms of the anchoring potential. The relation obtained is use to find the anchoring potential in the samples. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 1, 37–42 (10 January 1996)     

Optical time division multiplexing at 160 Gbps using MZI switching

Many lower-speed data streams can be multiplexed into one high-speed stream by means of optical time division multiplexing (OTDM), such that each input channel transmits its data in an assigned time slot. The simulation is performed by a fast multiplexer switch (mux). The routing of different data streams at the end of the TDM link is performed by a demultiplexer switch (demux) and this demultiplexer is employed using MZI switch as it consists a semiconductor optical amplifier (SOA) and an optical coupler. In this paper four channel OTDM is simulated at 40 Gbit/s and further the impact of the signal power, pulse width and control signal power on BER is investigated.     

The experimental facilities at ISAC

The ISAC accelerator facility provides rare isotope beams in three different areas at low (20–60 keV), medium-high (up to 1.8 AMeV) or higher energies (up to 16 AMeV, depending on the mass-to-charge ratio of the isotopes). There is a corresponding suite of experimental installations on the floor, most of them permanently, which are uniquely matched to the requirements of the scientific goals as well as to the conditions as the arise at rare-beam facilities, like ISAC. An introduction to the three distinct experimental areas, given by the available energy of beams, is given.     

Critical behaviour of the anchoring energy of the director at the free surface of a nematic liquid crystal

A new structural transition occurs at the free surface of some nematic liquid crystals when the temperature reaches a critical value T₀. In this work we study the temperature dependence of the anchoring energy of the director at the free surface close to the critical point. We find that the anchoring energy tends to zero with the critical exponent δ = 1 when the temperature approaches the critical value T₀. The experimental results are interpreted in terms of the Parsons and Mada theories.     

New experimental criterion of the Berezinskii-Kosterlitz-Thouless transition

Based on the experimental study of YBa₂Cu₃O_7?x single crystal nonlinearity near T _c , a new criterion for observing the Berezinskii-Kosterlitz-Thouless (BKT) transition in cuprate HTSC compounds was proposed. The criterion consists in the existence of the maximum in the dependence of the voltage of the second harmonic of the sample response signal excited by alternating current on the direct bias current. It was shown that the position of the second harmonic maximum is independent of temperatures near T _c , which is consistent with the BKT transition independence of the measuring current.     

Charmonium 2007: New experimental results

The most important experimental results in charmonium physics in the energy region above the threshold for open-charm production that were obtained in recent years are surveyed. The first measurements of the exclusive cross sections for e ⁺ e ^? → D \(\bar D\), D \(\bar D\)*, and D* \(\bar D\)* processes are discussed along with the discovered decay ψ(4415) → \(\bar D_2^* \)(2460). The properties of charmonium-like states, including the group of states Y (4260), Y (4325), and Y (4660) with quantum numbers of J ^PC = 1^??; the X(3940) and X(4160) states discovered in the process of double charmonium production in e ⁺ e ^? annihilation; and the X(3872), Y(3940), and Z ^±(4430) states found in B-meson decays, are presented.     

New experimental results in proton radioactivity

A review of experimental data obtained recently on proton-radioactive nuclei is presented. The highlights include the observation of fine structure in proton emission, for the decays of ¹³¹Eu, ¹⁴⁵Tm and ¹⁴⁶Tm, and the studies of the excited states in proton-emitting nuclei. The observation limits are extended to few nanobarns cross-sections ( ¹⁴⁰Ho, ¹⁶⁴Ir and ¹³⁰Eu) and few microsecond half-lives (e.g., ¹⁴⁵Tm). Measured decay properties for thirty-nine proton-emitting ground and isomeric states contributed to the understanding of nuclear masses and evolution of single-particle states at and beyond the proton drip line. Experimental results have stimulated new theoretical approaches to proton emission and the structure of unbound narrow resonance states. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: rykaczew@phy.ornl.gov