I. Kanazawa

Chemisorption of hydrogen into a graphite–potassium intercalation compound C8K studied by means of positron annihilation

The positron‐annihilation spectrum for C8K obtained from the Doppler broadening of the 511 keV annihilation radiation is composed of two Gaussian bands: one due to annihilation with electrons in the interlayer region, the other mainly due to annihilation with electrons in the graphitic layers. Upon introduction of hydrogen to C8K, both bands sharpened, which indicates a conversion of hydrogen atoms to hybride ions through charge transfer from the graphitic layers and the formation of positron–hydride ion complexes in the interlayer region. (AIP)

Structure and thermal stability of nanocrystalline silver studied by transmission electron microscopy and positron annihilation spectroscopy

Abstract Positron annihilation spectroscopy was carried out on nanocrystalline silver. Both lifetime and Doppler broadening were measured. High-resolution electron microscopy observations were also performed. Diffuse vacancy clusters, the sizes of which correspond to two to four vacancies, and voids of 1–5 nm diameter, were found to reduce the average atomic density of the grain boundary. Some grains grew to a diameter larger than about 70 nm during annealing the specimen from 50 to 100°C. A large fraction of the diffuse vacancy clusters and voids in the boundaries remained after annealing at 400°C. They were stabilized during annealing probably by gaseous atoms.

Gauge field and high-Tc superconductivity

Abstract It is shown that the massless U(1) gauge field Bμ3, which is derived from the carrion model, is much related to a linear T dependence of the resistivity in the normal state.

Quantized massive collective excitations, short-range spin fluctuations and high-Tc superconductivity

We have succeeded in quantizing massive collective gauge fields around the doped hole by using the theoretical formula, which is based on the gauge-invariant effective Lagrangian density, in underdoped cuprates. Quantized massive gauge fields, which are induced around the doped hole, explain naturally the broad spectra of angle-resolved photoemission around the hot spot, short-range spin fluctuations and anomalous transport properties in underdoped cuprates.

Production of an intense slow positron beam by using an electron LINAC and its applications

Abstract An image of reemitted positrons has been produced in a proto-type positron transmission-type reemission microscope by using the electrostatic intense slow positron beam from an electron LINAC. RHEPD experiments have then been performed on H-terminated Si(111).

Brightness enhanced intense slow positron beam produced using an electron linac

An intense pulsed slow positron beam was produced from a 100 MeV electron linac of the Japan Atomic Energy Research Institute and was extracted using solenoid transport tubes. The intensity of the obtained slow positron beam was 2–3×107 e+/s at 110 of the full power operation (at 10 μA average electron beam current). In order to use the beam for positron scattering, diffraction and microscope experiments, it was transferred from the solenoid magnetic field to a field-free region, and was then brightness-enhanced. The final beam size was reduced from 10 mm o in the solenoid magnetic field to 0.5 mm o after two stages of remoderation.

The boson peak in supercooled metallic liquids and glasses and relation to the glass transition

We have presented a theory of three-dimensional supercooled metallic liquids and glasses, which is based on the gauge-invariant Lagrangian density with spontaneous breaking (Higgs mechanism), and compared it with the frustration-limited domain (FLD) theory. Using the present theoretical formulation, a qualitative picture of the boson peak is proposed.

Carrions, spin disorder state, and high-Tc superconductors

Abstract It is discussed that the interaction between two holes for the Cooper pair formation is derived from the exchange of the gauge fields Bμ, which are introduced in the carrion model based on the gauge-invariant effective Lagrangian density.

Positron annihilation in a hydrogen-physisorbed graphite-caesium intercalation compound

Abstract The annihilation spectrum for CsC 24 obtained from the Doppler broadening of 511 keV γ-radiation consists of a narrow band superimposed on a broad band. Upon hydrogen physisorption at 77 K, the spectral height decreased. These facts are explained in terms of an interlayer state, the electrons of which are blocked to interact with positrons through the hydrogen physisorption.

Positron annihilation in graphite-alkali metal-hydrogen ternary systems

Abstract Chemisorption and physisorption of hydrogen into the graphite-alkali metal intercalation compounds, KC 8 and CsC 24 , were studied by means of positron-annihilation. The changes of the annihilation spectra obtained from the Doppler-broadening, upon hydrogen-introduction to the compounds, were explained in terms of changes in the positron-electron-annihilation probability in the intercalate layers of graphite.