Search results for "IONIZATION"
showing 10 items of 1255 documents
On the sensitivity of ion traps for spectroscopic applications
1979
Ba+ ions, created by surface ionization near one endcap of an rf quadrupole trap were slowed down by collisions with the background gas. At He pressures of 10−6 mbar or more 2% of the primary ions could be trapped. The sensitivity of ion detection by fluorescence radiation allows spectroscopic experiments, starting from less than 107 particles. The observation of the ground-state hyperfine splitting of137Ba+ is given as an example.
Optimization and analysis of processes with moving materials subjected to fatigue fracture and instability
2013
We study systems of traveling continuum modeling the web as a thin elastic plate of brittle material, traveling between a system of supports at a constant velocity, and subjected to bending, in-plane tension and small initial cracks. We study crack growth under cyclic in-plane tension and transverse buckling of the web analytically. We seek optimal in-plane tension that maximizes a performance vector function consisting of the number of cycles before fracture, the critical velocity and process effectiveness. The present way of applying optimization in the studies of fracture and stability is new and affords an analytical tool for process analysis. peerReviewed
Metallization of the Na 14 Cl 13 Cluster
1994
The structure and energetics of multiple-excess-electron alkali halide clusters Na14Cl14-n, (1 ≤ n ≤ 6) is studied by ab initio calculations using norm-conserving pseudopotentials and local-spin-density-functional theory. Analysis of various electronic properties (Kohn-Sham one-electron eigenvalue spectra, ionization potentials, participation ratios of Kohn-Sham orbitals), as well as multiple F-center formation energies, suggests that these clusters can be characterized as Nan(NaCl)14-n having a "phase-separated" metallic part NaI. The Na14Cl9 (or Na14Cl9+) cluster exhibits a face (surface) segregated metallic Na5 (Na5+) overlayer, the stability of which is demonstrated by a molecular-dynam…
Time-dependent effects in the nonsequential ionization of helium at various wavelengths
2000
Calculations of the double ionization of a model 1D helium atom interacting with an intense short laser pulse are presented. A substantial signature of nonsequential double ionization is found for all the wavelengths that are considered, from 248 nm to 1064 nm, provided that sufficiently short pulses are employed. We show how one can modify the size of the “knee” structure of the double ionization yield curve by varying the laser pulse duration. The underlying mechanism of the correlated double electron ejection is investigated and discussed.
Electronic Structure Changes across the Metamagnetic Transition in FeRh via Hard X-Ray Photoemission
2012
International audience; Stoichiometric FeRh undergoes a temperature-induced antiferromagnetic (AFM) to ferromagnetic (FM) transition at similar to 350 K. In this Letter, changes in the electronic structure accompanying this transition are investigated in epitaxial FeRh thin films via bulk-sensitive valence-band and core-level hard x-ray photoelectron spectroscopy with a photon energy of 5.95 keV. Clear differences between the AFM and FM states are observed across the entire valence-band spectrum and these are well reproduced using density-functional theory. Changes in the 2p core levels of Fe are also observed and interpreted using Anderson impurity model calculations. These results indicat…
Ionization potential of aluminum clusters
1998
Structure, electronic structure, and ionization potential of aluminum clusters of 2–23 atoms are studied with a total energy method based on the density-functional theory. The calculated adiabatic ionization potentials agree remarkably well with the data from threshold photoionization measurements. The analysis of results gives insight into hybridization effects in the smallest clusters as well as reveals certain clusters that exhibit a clear jellium-type shell structure. An explanation of the experimental results in the size region of 12–23 atoms is given in terms of coexisting, competing icosahedral, decahedral, and fcc-based clusters. @S0163-1829~98!00228-8#
Hydrogen-like bismuth
1995
Atomic physics at heavy ion storage rings allows to study matter in an extreme ionization state and at very high velocity. The concept of electron cooling yields an ion beam with epithermal temperatures, which is suited for many precision experiments. At the ESR even the heaviest elements can be stored up to the fully stripped charge state. The H-like ions with nuclear spin exhibit a groundstate hfs-splitting in the optical region. This can be used as a probe for QED at high Z and magnetization inside the nucleus. The topics related to cooling of ions and laser spectroscopy in a storage ring are reported and a first result of the 1s hfs in 209Bi82+ is discussed for the relevance in testing …
The laser ion source trap for highest isobaric selectivity in online exotic isotope production
2010
The improvement in the performance of a conventional laser ion source in the laser ion source and trap (LIST) project is presented, which envisages installation of a repeller electrode and a linear Paul trap/ion guide structure. This approach promises highest isobaric purity and optimum temporal and spatial control of the radioactive ion beam produced at an online isotope separator facility. The functionality of the LIST was explored at the offline test separators of University of Mainz (UMz) and ISOLDE/CERN, using the UMz solid state laser system. Ionization efficiency and selectivity as well as time structure and transversal emittance of the produced ion beam was determined. Next step aft…
ECRIS plasma spectroscopy with a high resolution spectrometer
2020
Electron Cyclotron Resonance Ion Source (ECRIS) plasmas contain high-energy electrons and highly charged ions implying that only noninvasive methods such as optical emission spectroscopy are reliable in their characterization. A high-resolution spectrometer (10 pm FWHM at 632 nm) enabling the detection of weak emission lines has been developed at University of Jyväskylä, Department of Physics (JYFL) for this purpose. Diagnostics results probing the densities of ions, neutral atoms, and the temperature of the cold electron population in the JYFL 14 GHz ECRIS are described. For example, it has been observed that the cold electron temperature drops from 40 eV to 20 eV when the extraction volta…
Time profile of ion pulses produced in a hot-cavity laser ion source.
2010
The time spreads of Mn ions produced by three-photon resonant ionization in a hot-cavity laser ion source are measured. A one-dimensional ion-transport model is developed to simulate the observed ion time structures. Assuming ions are generated with a Maxwellian velocity distribution and are guided by an axial electric field, the predictions of the model agree reasonably well with the experimental data and suggest that the ions are radially confined in the ion source and a substantial fraction of the ions in the transport tube are extracted.