Two Beam Coupling in Semi-Insulating GaN Film Using Electroabsorption Effect

The photorefractive effect was observed in He-ion-implanted semi-insulating GaN film in the UV spectral region. The photorefractive grating is induced by the electroabsorption effect near the band-edge. Two beam coupling experiments were performed at a wavelength of 363.8 nm. The experimental results indicate that absorption grating mainly contributes to the beam coupling.     

Adsorption behavior of metal ions onto a bovine serum albumin (BSA) membrane monitored by means of an electrode-separated piezoelectric quartz crystal.

The interaction between metal ions and bovine serum albumin (BSA) was studied by using a piezoelectric quartz crystal (PQC) arranged in the electrode-separated configuration. A silanized surface of the PQC was coated with a BSA membrane via a coupling reaction with glutaraldehyde. The frequency shifts obtained from PQC coated with a BSA membrane suggested that various kinds of metal ions could be adsorbed onto the BSA membrane from aqueous solutions containing a low concentration of metal ions (2 or 10 micromol dm(-3)), only when the BSA was denatured with an alkaline solution. Anionic species of Pt(IV) and Au(III) were adsorbed onto the denatured BSA membrane from an acetic acid solution at pH 2.2, and cationic species of Cd(II), Zn(II), Co(II), Ni(II), Cu(II), and Ag(I), and cations, such as Ca2+, Ba2+, and Mg2+, were adsorbed from ammonia buffer at pH 9.5, whereas Al(III), Cr(III), Fe(III), Hg(II), and Pb(II) were hardly adsorbed. The adsorption mechanisms of these metal ions are discussed, based on the electrostatic interaction between the metal ions and the denatured BSA membrane, and complex formation between the metal ions and amino acid residues of the denatured BSA. Further, the PQC coated with a denatured BSA membrane was applied to the determination of Pt and Cd, using large frequency shifts for Pt(IV) and Cd(II).     

Comparative Study of Electrodeposited and Ion Beam Mixed Fe-Ni-Cr Alloys

Electrodeposited Fe-Ni-Cr alloys irradiated with 209 MeV energy ⁸⁴Kr ions were investigated by conversion electron Mössbauer spectroscopy, X-ray diffraction and electron microprobe analysis. Significant dose dependent changes were found between Mössbauer spectra of the irradiated and non-irradiated deposits. These changes reflect the dose dependent transformation of the metastable ferromagnetic phase to the paramagnetic one.     

A new fast type of Mössbauer spectrometer for the rapid determination of iron-bearing minerals used in the paint industry

A new miniaturised Mössbauer spectrometer has been developed for laboratory and industrial application. Equipped with a YAIO₃:Ce crystal fast scintillation detector unit and mini transducer for the energy modulation of gamma rays, the unique mechanical design enhances protection from radiation and prevents disturbance by mechanical vibrations. It can be used with various types of cryostat and furnace.Supported by the LabVIEW graphical programming environment and by the new algorithm for the quantification of iron-components, the spectrometer can be used as a single-purpose instrument for the rapid determination of the Fe²⁺/Fe³⁺ ratio in ilmenite and Morin transition temperature of hematite. It can also be used to monitor the manufacturing processes for titanium white and copperas red.     

Possible new approaches to superheavy elements — the (HI,αχn) reaction and the neutron-rich beam

We first report the recent experiment on the²³²Th(⁴⁰Ar,α3n)²⁶⁵[106] reaction carried out at RIKEN to test the usefulness of the (HI,αχn)-type reaction for the production of very heavy elements. Reaction residues recoiling out of a thin ThO₂ target bombarded with 5.2 MeV/u⁴⁰Ar beam were separated from the beam by using a gas-filled recoil separator and implanted onto a two-dimensionally position-sensitive solid-state detector placed at the focal plane of the separator. The preliminary results of the analysis show that the cross section of the above reaction is around 1 nb, being about four times larger than that of the²⁴⁸Cm(²²Ne,5n)²⁶⁵[106] reaction reported in the literature. Secondly, we discuss briefly the merits and demerits of the use of a neutron-rich beam for the production of superheavy elements, in which we stress the possibility that the demerit of weak secondary-beam intensity is nearly cancelled out by the increase of the survival probability with the increase of the neutron number of the compound nucleus and also by the possible enhancement of near-barrier fusion.     

CEMS Study on Fe Films Deposited by Laser Ablation

Iron thin films deposited on Al foil by pulsed laser ablation were characterized by conversion electron Mössbauer spectrometry (CEMS). The hyperfine fields became large and the isomer shift was closed to that of bulk α-Fe with increasing the thickness of deposited films. The small grains are so reactive that small particles of Fe^III oxides were produced in thin deposited layers. The magnetic orientation of the deposited films became from parallel to in-plane to at random. The small grains were considered to grow by aggregating with ablation time.