Electrical and optical properties of chalcogenide amorphous semiconductors modified with Ni

The electrical and optical properties of the chalcogenide semiconductor (Se₃₂Te₃₂As₄Ge₃₂)_100?xNixitx have been studied. As the Ni concentration is increased the electrical dc conductivity is drastically increased and variable range hopping conduction becomes dominant even above room temperature. The optical energy gap decreases with the Ni concentration from 1.18–0.95 eV. Ni-atoms in the chalcogenide semiconductor donate free electrons which occupy the gap state. This occupation causes the shift of the Fermi level toward the conduction band. It is an effect of this shift that the thermal activation energy is decreased. The decrease in optical energy gap is independent of the shift of the Fermi level and is ascribable to the appearance of the additional level located at 0.95 eV above the top of the valence band. This level originates from the 3d-level of the Ni-atom.     

Graphical representation of the solutions of the schrödinger equations for a particle in various model potentials

Several one-dimensional Schrödinger equations for a particle trapped in various model potentials are solved analytically or approximately, and the results are plotted by an X—Y plotter. Typical results are illustrated. Several interesting features of the relations between the shape of the potential and the solution of the Schrödinger equation are pointed out. Combination of these results allows reasonable guesses about the forms of the energy levels and wavefunctions for complicated but realistic problems.     

Studies on neutron activation analysis using ion exchange preconcentration

Three convenient procedures are described for applying anion exchange resins to the preconcentration and irradiation support in neutron activation analysis. For each procedure the amounts of interferences were determined. The effect of the form, cross-linkage, pore size, and particle size of the resins on the elimination of interferences was investigated. Some other associated problems are also presented, viz. effect of concentration and temperature of washing solution, effect of irradiation time, and comparison with filter     

Development of high-radiation-sensitive polymer gel for magnetic resonance imaging in three-dimensional dosimetry

We developed a high radiation sensitive polymer gel by modifying the amounts of the gel components and the temperature for the gel preparation. We evaluated its relaxation time linearity against dose and compared the measured dose distribution with the calculated one. For the relaxation time-dose linearity, irradiations were carried out with a linear accelerator using 6 MV photons and doses ranging from 0-5.0 Gy. The relationship between dose and R(2) value (reciprocal of T(2) relaxation time) was measured and it had good linearity over a wide range (0.3-5 Gy). The measured dose distributions were in good agreement with calculated ones. Since the present gel has higher sensitivity and it is synthesized more easily at lower cost than conventional polymer gels, we expect to see improved three-dimensional (3D) dosimetry using it.     

Real-time charge oscillation between monomers in a dimeric system associated with intermolecular vibration induced by an ultrashort pulse

Ultrafast charge resonant (CR) dynamics between two molecules in a dimer system has been studied theoretically and experimentally using 6-fs laser pulses and a thin film of amorphous-phase phthalocyanine tin(IV) dichloride (SnPc). The modulation of the absorbance change in the bleaching spectral range of the CR absorption band was analyzed to obtain the amount of charge resonantly transferred back and forth by a dimeric vibration induced by photoexcitation. The modulation can be explained in terms of a periodic change in the cross section and a periodic energy shift, where both are induced by the change in the overlap integral caused by the accordion-type intermolecular vibration. The associated change in distance between two molecules with the intermolecular vibration was estimated to be 0.09 A, which corresponds to 2.5% of the mean distance between the two SnPc molecules in the dimeric system.     

Carrier-envelope phase-controlled quantum interference in optical poling

We demonstrate the efficiency of the optical poling process that depends on the CE phase-controlled quantum interference. For the experiment we employed our noncollinear optical parametric amplifier system for the self-stabilization of the CE phase, with the f-to-2f spectral interferometry system to control the CE phase.     

Reactive barium-promoted Reformatsky-type reaction of alpha-chloroketones with aldehydes

A Reformatsky-type aldol reaction of alpha-chloroketones with aldehydes has been achieved using reactive barium as a low-valent metal in THF; this one-pot process is more effective for obtaining the desired beta-hydroxy ketones in high yields than the stepwise process in which barium enolates are prepared prior to the reaction with aldehydes.     

Iridium complex-catalyzed highly enantio- and diastereoselective [2+2+2] cycloaddition for the synthesis of axially chiral teraryl compounds

An asymmetric [2+2+2] cycloaddition of an alpha,omega-diyne, possessing ortho-substituted aryl groups on its terminus, and a monoalkyne with oxygen functionalities gave various axially chiral teraryl compounds. The coupling proceeded with extremely high enantio- (>99.5% ee) and diastereoselectivities (dl/meso = >95/5) when catalyzed by an iridium-chiral phosphine complex. As the products were readily transformed into diol compounds by deprotection without racemization, the present procedure provides access to a new chiral pool of diol compounds with C2 symmetry.