Development of non-destructive isotopic analysis methods using muon beams and their application to the analysis of lead

Journal of Radioanalytical and Nuclear Chemistry - Elemental isotopic ratios are measured in various research fields and provide useful information regarding age, origin, geological and biological...     

Absorption spectroscopy of uranium plasma for remote isotope analysis of next-generation nuclear fuel

CdSe/Se multilayer thin films were prepared using sequential thermal evaporation technique by varying the thickness of selenium sublayers. Identifying the prominent peaks observed in the XRD spectra of the top layer CdSe which corresponds to the (100) plane with wurtzite structure, the average size of the crystallites was calculated for the CdSe nanocrystals. Experimentally measured band gaps are larger than bulk band gap of CdSe. This confirms the presence of spin-orbit splitting of energy levels. Size of the crystallites was then calculated with the theoretical prediction of the effective mass approximation model (i.e., Brus model). It resulted in that the diameters of crystallites were much smaller than the Bohr exciton diameter (11.2 nm) of CdSe. Thus the structural and optical properties of CdSe/Se multilayer thin films reveal the effect of quantum confinement of CdSe crystallites in Se matrix for various sublayer thicknesses. Confinement effect is more pronounced while sublayer thickness of selenium increases.     

Formation of ionic bonds between a fatty-acid Langmuir-Blodgett monolayer and a zinc oxide substrate

A fatty-acid Langmuir-Blodgett (LB) monolayer ionically adsorbed to the substrate has been prepared by adopting ZnO-based conductor and pure water respectively as the substrate and subphase. Ionization of the fatty-acid molecules has been detected by infrared reflection-absorption spectroscopy (IR-RAS), which is enabled by the condensed free electrons in the doped ZnO substrate. On the contrary, IR-RAS measurements have indicated that fatty-acid molecules transferred onto Au and indium-tin-oxide substrates from a pure-water surface are not ionized. In addition, it has been demonstrated that these ionically bonded fatty-acid monolayers protect the ZnO transparent electrode from chemical attack by NH(3) gas. Since the LB technique is a simple method applicable to a wide variety of materials, the present results may lead to a new way of obtaining functional organic-inorganic nanosystems.     

Ionography of nanostructures with the use of a laser plasma of cluster targets

It has been shown that a femtosecond plasma of cluster targets is an almost isotropic source of fast ions and, hence, can be used to obtain ionographic images with a wide field of view. The spatial resolution of the resulting ionographic images is no worse than 600 nm, which corresponds to a uniquely high value of about 105 of the ratio of the field of view to the resolution. The use of 100–300-keV ion fluxes ensures the sensitivity of the method to the sample thickness of no worse than 100 nm even for samples consisting of light chemical elements (C, H). The proposed method can be used to obtain images of low-contrast biological objects, thin films, membranes, and other nanostructured objects.     

Muonic X-ray measurements on mixtures of CaO/MgO and Fe3O4/MnO

Journal of Radioanalytical and Nuclear Chemistry - Elemental analysis by measurement of muonic X-rays shows great potential for analyzing the elemental composition of a bulk material at a specific...     

Transient electrostatic fields and related energetic proton generation with a plasma fiber

We observe a hollow structure and a fine ring in the proton images from a petawatt scale laser interaction with a "cone-fiber" target. The protons related to the hollow structure are accelerated from the cone-tip surface and deflected later by a radial electric field surrounding the fiber. Those associated with the fine ring are accelerated from the fiber surface by this radial electric field. This field is found to decay exponentially within 3 ps from about 5 x 10(12) V/m. Two-dimensional particle-in-cell simulations produce similar proton angular distributions.     

Direct observation of nitrogen location in molecular beam epitaxy grown nitrogen-doped ZnO

ZnO is a wide band gap, naturally n-type semiconductor with great promise for optoelectronic applications; the main obstacle yet to be overcome is p-type doping. Nitrogen, the most promising candidate currently being pursued as a dopant, has been predicted to preferentially incorporate into the ZnO lattice in the form of a N-2 molecule at an O site when a plasma source is used, leading to compensation rather than p-type doping. We demonstrate this to be incorrect by using N K-edge x-ray absorption spectra and comparing them with first-principles calculations showing that nitrogen, in fact, incorporates substitutionally at O sites where it is expected to act as an acceptor. We also detect the formation of molecular nitrogen upon annealing. These results suggest that effective p-type doping of ZnO with N may be possible only for low-temperature growth processes.     

Development of a non-destructive isotopic analysis method by gamma-ray emission measurement after negative muon irradiation

Journal of Radioanalytical and Nuclear Chemistry - Variations in isotopic abundance provide useful information for various scientific fields. Herein we performed a feasibility study by...