Argon (10 keV) scattered from structures,induced by bombarding a Cu(100) surface; ionization and neutralization

The ion fractions, η⁺, of 10 keV argon particles, scattered from a damaged copper surface, are measured with a time of flight spectrometer. The damage was introduced by bombardment with argon ions. The scattering angle was 30°. The results for different angles of incidence, ψ, are reported. For Ψ < 10° the ion fraction is relatively high (～27% for Ψ = 4°) and decreases as Ψ increases. For Ψ = 15° the value of η⁺ is 7%, whereas for 21° < Ψ < 27° the value of η⁺ appears to be constant (～14%). An explanation is given by assuming interatomic ionization as well as neutralization processes along the trajectory of the scattered particles. The number of step-atoms, induced by ion bombardment, is estimated to be about 2 × 10¹⁴/cm².     

Luminescence of interstitial atomic hydrogen in KBr and RbBr doped with I-

In KBr and RbBr doped with OH^- and I^- interstitial atomic hydrogen was produced in a configuration in which it is surrounded tetrahedrally by 3 Br^- and 1 I^- ions. Excitation in the absorption bands leads to a blue-green and an infrared fluorescence band (KBr: 2.53 and 1.35 eV). The absorption spectrum consists of 3 I-type and 1 broad Br-type charge transfer bands as could be shown from the excitation spectrum. The emission occurs only from relaxed I-type charge transfer states with a transition moment along the connection line H^o-I^-. The results are discussed with a simple charge transfer model.In mit OH^- and J^- dotiertem KBr und RbBr wurde atomarer Wasserstoff auf Zwischengitterplatz in einer Konfiguration hergestellt, in welcher er tetraedrisch von 3 Br^-- und 1 J^--Ion umgeben ist. Anregung in den Absorptionsbanden führt zu einer blaugrünen und einer infraroten Fluoreszenzbande (KBr: 2,53 und 1,35 eV). Das Absorptionsspektrum besteht aus 3 jodartigen und einer breiten, bromartigen Charge-Transfer-Bande, wie mit Hilfe des Anregungsspektrums gezeigt werden konnte. Die Emission erfolgt nur aus den relaxierten, angeregten, jodartigen Charge-Transfer-Zuständen mit dem Übergangsmoment parallel zur Verbindungslinie H^o-I^-. Die Ergebnisse werden anhand eines einfachen Charge-Transfer-Modells diskutiert.     

Nucleon transfer reactions to rotational states induced by206, 208Pb projectiles

In a systematic study of nucleon transfer reactions accompanied by Coulomb excitation we have bombarded¹⁵²Sm,¹⁶⁰Gd and²³²Th with^{206, 208}pb beams at incident energies close to the Coulomb barrier. Particle-gamma coincidence techniques were used to identify excited states of reaction products populated through inelastic scattering and in nucleon transfer reactions. One-neutron stripping and pick-up reactions on¹⁵²Sm were observed leading to known states of the rotation alignedi _13/2-bands in¹⁵³Sm and¹⁵¹Sm. In the¹⁶⁰Gd+^{206, 208}Pb systems no significant population of low lying states of product nuclei was found in the nucleon-transfer channels. Large cross sections were observed for one- and two-neutron pick-up from²³²Th at an incident energy of 6.4 MeV/u. Around the grazing angle they are of the same order of magnitude as the cross section measured for inelastic scattering. The results are analyzed in the framework of semiclassical models.     

Exotic nuclei produced by heavy-ions induced fission

About thirty nuclei in theA≈100 mass region have been produced as fission fragments following the fusion-evaporation reactions^28,30Si+¹⁷⁶Yb at 145 MeV bombarding energy. These nuclei have been individually identified from their γ-ray cascades detected with the Eurogam2 array. The level schemes of several stable or neutron-rich nuclei have been extended to higher spins. From cross coincidences between transitions in complementary fragments, γ-rays de-exciting high-spin states of new isotopes can be identified and some aspects of the fission mechanism can be analyzed.     

Optimum oxide thickness for dye-sensitized solar cells—effect of porosity and porous size. A numerical approach

The microstructure of the metal semiconductor oxide which forms the heart of a dye-sensitized solar cell (DSSC) has proved to play a key role in the enhancement of photoelectric conversion efficiency of the cell. In this work, a numerical simulation of the system TiO₂ photo-sensitive dye of a TiO₂ DSSC focuses on the effect that the oxide porosity and the size of the pores have on the cell's performance. The steady-state numerical model used is based on the continuity and transport equations for charge species involved in the system, in connection to Poisson's equation. Light absorption coefficient is set dependent on both porosity and the size of pores in TiO₂. At a first approximation, electron mobility is considered dependent upon porosity following an iteration procedure dependent also upon local field in the oxide. An effective dielectric constant dependent upon the porosity of TiO₂, as well, is used in the model. Electron lifetime in the bulk is set dependent upon electron distribution following the iteration procedure with electron lifetime at the surface taking into consideration surface recombination. Results for different values of TiO₂ porosity and pores' size in connection to the oxide thickness are discussed and found in accordance with results reported in the literature.     

Microwave Plasmas at Atmospheric Pressure

Microwave plasmas at atmospheric pressure are used for surface treatments like for example cleaning, sterilization or decontamination purposes, for a pre‐treatment to increase the adhesion of lacquer, paint, or glue, and for the deposition of different kind of layers and coatings. Micro plasma jets can also be applied for biomedical applications and for treatment of small and complex geometries like for example the inside of capillaries. Larger plasma torches which exhibit higher gas temperatures can also be used for chemical syntheses like waste gas decomposition, methane pyrolysis, or carbon dioxide dissociation and for plasma spraying purposes. In the present publication an overview on the development and the investigation of the operating principle of two atmospheric pressure microwave plasma torches at frequencies of 2.45 GHz and 915 MHz will be presented. The plasma sources are based on a cylindrical resonator combined with coaxial structures. To explain how these plasma sources work, simulations of the electric field distribution will be discussed. Furthermore, some physical characteristics of an air and an Ar/H2 atmospheric plasma like gas temperatures, excitation temperatures and densities as well as the heating of the plasma by the microwave will be investigated. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Intercomparison of the response of different photon and neutron detectors around a spent fuel cask

An intercomparison of the response of different photon and neutron detectors was performed in several measurement positions around a spent fuel cask (type TN 12/2B) filled with 4 MOX and 8 UO₂ 15 × 15 PWR fuel assemblies at the nuclear power plant Gösgen (KKG) in Switzerland. The instruments used in the study were both active and passive, photon and neutron detectors calibrated either for ambient or personal dose equivalent.The aim of the measurement campaign was to compare the responses of the radiation instruments to routinely used detectors.It has been shown that especially the indications of the neutron detectors are strongly dependent on the neutron spectra around the cask due to their different energy responses. However, routinely used active photon and neutron detectors were shown to be reliable instruments.