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.     

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.     

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.     

Time-resolved measurements of intramolecular energy transfer in single donor/acceptor dyads

We have investigated electronic excitation energy transfer in a specifically designed bichromophoric donor/acceptor dyad in which the donor (perylenediimide) and acceptor (terrylenediimide) are linked by a rigid heptaphenyl-spacer. Because of the choice of the bridge, which defines the distance and orientation of the two chromophores, donor as well as acceptor emission is observed. The significantly smaller photostability of the donor allows for time-resolved measurements of the acceptor emission at the single-molecule level with and without energy transfer from the donor. By analyzing the differences of the rise/decay profiles for both pathways, we could determine time constants of energy transfer with high accuracy for single dyads. The results show that the experimental approach presented here works even for situations in which the energy transfer times are smaller than the temporal resolution of the detection system.     

An analytically useful coulometric generation of micro amounts of metal ions : Part I. Electrogeneration of bismuth(III)

Bismuth(III) can be generated in a solution by electrolytically oxidizing dilute bismuth amalgam. Oxygen present in the solution contacting the amalgam also oxidizes the amalgam. Therefore normal coulometric circuits are not suitable for the generation of trace quantities of bismuth(III), even after prolonged passage of nitrogen. A procedure is described by which the interference of oxygen is eliminated so that amounts of bismuth(III) down to 5·10^-8 moles (in 30 ml) can be generated with 100% current efficiency.