Raman scattering in the depletion region of GaAs

We have obtained spectra for the LO phonon mode by Raman scattering associated with surface quantization of the hole states in the depletion layer of highly doped n-type GaAs samples. When semi-transparent metal contacts are employed, the zone-center LO peak shifts to higher frequency due to plasmon-phonon interaction. The observed effects are not sensitive to the types of metal. The presence of the plasmon mode is thought to be due to the steady-state carrier injection from the incident laser light. The position of the peak is used to estimate the surface recombination rate of the excited electron-hole pairs.     

Enhancement of ohmic and stochastic heating by resonance effects in capacitive radio frequency discharges: a theoretical approach

In low-pressure capacitive radio frequency discharges, two mechanisms of electron heating are dominant: (i) Ohmic heating due to collisions of electrons with neutrals of the background gas and (ii) stochastic heating due to momentum transfer from the oscillating boundary sheath. In this work we show by means of a nonlinear global model that the self-excitation of the plasma series resonance which arises in asymmetric capacitive discharges due to nonlinear interaction of plasma bulk and sheath significantly affects both Ohmic heating and stochastic heating. We observe that the series resonance effect increases the dissipation by factors of 2-5. We conclude that the nonlinear plasma dynamics should be taken into account in order to describe quantitatively correct electron heating in asymmetric capacitive radio frequency discharges.     

Novel N,N,P-tridentate ligands for the highly enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones

Use of 0.25 mol % of the N, N, P-tridentate ligand containing the 2-quinolyl moiety ( 1 and 2) and 0.1 mol % of Cu(OTf) 2 enabled the enantioselective 1,4-addition of dialkylzincs to cyclic enones to produce 1,4-adducts in up to 99% ee.     

Synthetic studies toward biselides. Part 2: synthesis of the macrolactone part of biselides A and B using allylic oxidation

Synthesis of the macrolactone part of biselides A (1) and B (2), marine cytotoxic polyketides, was achieved by using regioselective allylic oxidation as a key step.     

Application of a conproportionation reaction to a synthesis of shape-controlled gold nanoparticles

Synthesis of gold nanoparticles with multiple shapes by a modified seeding growth method is reported. The optical extinction spectra of a mixture of the seed and growth solutions indicate that the seed particle size decreases during stirring the mixture by a conproportionation reaction of Au metal with Au(III) ions. This conproportionation reaction is used to investigate the effects of variation in seed particle size on the resultant gold nanoparticle shape. When single crystalline and multiply twinned particles are used as the seed particles, they grow into gold nanorods and nanobipyramids, respectively. By letting the seed particles experience the conproportionation reaction before the particle growth to decrease the size, the surface of resultant nanoparticles roughens. Increasing the conproportionation reaction time up to 5 min, multi-branched gold nanoparticles with many lattice defects grow from both of the seed particles. This indicates that the conproportionation reaction is useful to generate lattice defects during the particle growth, which lead to the formation of gold nanoparticles with complex shapes.     

Precise nuclear moments of extremely proton-rich nuclus 23 Al

Electric quadrupole coupling constant eqQ/h of the extremely proton-rich ²³Al (I ^π ?=?5/2^?+?, T _1/2?=?0.47 s) nucleus implanted into an Al₂O₃ single crystal has been measured for the first time, using the β-ray detecting nuclear quadrupole resonance method (β-NQR) in a high magnetic field. As a preliminary result, the quadrupole coupling constant was determined as |eqQ/h(²³Al) |?=?2.66±0.77 MHz. Using the quadrupole coupling constant of ²⁷Al in Al₂O₃ as a reference, the Q moment of the ground state of ²³Al was extracted as |Q(²³Al)|?~?160 mb, which is well explained by the shell model calculation in the sd-shell model space with the USD interaction.