Demonstration of highly efficient broadband amplification in a optical parametric chirped-pulse amplifier system

We have demonstrated highly efficient broadband amplification by an optical parametric chirped pulse amplifier (OPCPA) system that uses high energy seed pulses. The OPCPA consists of three type I B-barium borate (BBO) crystals pumped by a Q-switched Nd:YAG laser. We successfully amplified the microjoule level seed pulses to 78 mJ with a pump-to-signal optical conversion efficiency of 26% at a 10 Hz repetition rate. To our knowledge these results represent the most optically efficient OPCPA to date pumped by a typical Q-switched laser.     

Photon recycling transport in bulk GaAs probed by μSR with laser irradiation

A newly developed μSR method combined with a tunable, high power and sharply pulsed laser was applied to GaAs. Anomalous transport phenomena of the photo excited effects into bulk crystal were observed, given that the stopping range of implanted muons is about 200 times larger than photo-absorption depth. In addition, the measurement of photon energy dependence of muon spin depolarization under laser irradiation suggests the impurity level associated with Mu _BC ⁰ is located within the band gap of GaAs. This revised version was published online in August 2006 with corrections to the Cover Date.     

Muonium quadrupole interaction in ferroelectric substances KDP and KHCO3

The muonium quadrupole interaction is determined in KDP and KHCO₃. Using single crystal the field gradient tensor was obtained from muonium precession under the transverse field at room temperature. The muonium signal relaxes very fast at lower temperature, from this temperature dependence the dynamics of muonium was obtained. This revised version was published online in August 2006 with corrections to the Cover Date.     

Alkylamines‐intercalated α‐zirconium phosphate as latent thermal anionic initiators

The reaction of glycidyl phenyl ether (GPE) with 1‐aminoalkanes‐intercalated α‐zirconium phosphate (α‐ZrP·1‐aminoalkane): 1‐aminoalkanes 1‐aminopropane (α‐ZrP·Pr), 1‐aminobutane (α‐ZrP·Bu), 1‐aminooctane (α‐ZrP·Oct), and 1‐aminohexadecane (α‐ZrP·Hed) was carried out at varying temperatures for 1 h periods. Reaction progress was not observed until the reactants were heated to 80 °C or above. On increasing the temperature, the conversion factors increased such that, at 140 °C, conversions of 62% (α‐ZrP·Pr), 60% (α‐ZrP·Bu), 67% (α‐ZrP·Oct), and 64% (α‐ZrP·Hed) were obtained. The thermal stabilities as latent initiators were tested: GPEs reacted with α‐ZrP·Pr, α‐ZrP·Bu, and α‐ZrP·Oct at 40 °C for 360 h achieved conversions of 83, 55, and 59%, respectively. In contrast, the reaction in the presence of α‐ZrP·Hed did not proceed at 40 °C. The order of the thermal stability of GPE in the presence of α‐ZrP·1‐aminoalkane intercalation compounds was: α‐ZrP·Hed > α‐ZrP·Bu ≈ α‐ZrP·Oct > α‐ZrP·Pr. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1854–1861     

CompX,a luciferin-related tyrosine derivative from the bioluminescent earthworm Fridericia heliota. Structure elucidation and total synthesis

A luciferin analog, CompX, was isolated from the extracts of the bioluminescent earthworm Fridericia heliota. Its structure was determined as (Z)-5-(2-carboxy-2-methoxyvinyl)-2-hydroxybenzoic acid by spectroscopic data analysis and was confirmed by total synthesis. The (Z)-configuration of the double bond was established by comparing the ROESY spectra of CompX with those of its synthetic (E)-isomer. CompX represents a tyrosine analog, not previously found in natural sources, and is probably derived from tyrosine by deamination, O-methylation of the resulting alpha-keto acid, and carboxylation at the aromatic core.     

AsLn2, a luciferin-related modified tripeptide from the bioluminescent earthworm Fridericia heliota

AsLn2, an unusual modified peptide, was isolated from the bioluminescent earthworm Fridericia heliota (Enchytraeidae). Its structure, elucidated by NMR and mass spectrometry, includes residues of tyrosine, CompX (a novel tyrosine modification product, reported in the accompanying paper), and N(omega)-acylated lysine. Chromatography, UV, and ¹H NMR data imply a close structural similarity of AsLn2 with F. heliota luciferin. AsLn2 appears to be an intermediate or by-product in F. heliota luciferin biosynthesis.     

Radiation-detected optical pumping in solids

Radiation-detected optical pumping in solids has been developed to investigate the structure of unstable nuclei. Appreciable nuclear polarization of implanted or doped unstable-nuclei in a host crystal is achieved with the optical pumping in solids. The nuclear polarization achieved is enhanced/reduced by applying a radio-frequency magnetic field together with the optical pumping, radiation-detected magnetic resonance being thus observed to get information on electromagnetic properties of unstable nuclei. Two schemes have been successfully developed for the optical pumping of unstable nuclei in solids. One is to directly pump the atoms by the excitation from the ground state to a broad absorption band in visible and UV regions which shows a large magnetic circular dichroism. This scheme is applicable to many rare-earth atoms in alkaline-earth fluoride host. The other scheme is to pump the electrons in the conduction band of direct-type semiconductor and thus indirectly polarize the nuclei in the host material via a hyperfine interaction between the nuclei and the polarized conduction electrons. This scheme can be especially applied to the III to VI families of atoms in direct-type semiconductors. Principle of the methods, on-line experimental system, and a few examples of the results obtained so far are presented and discussed.     

Backward polarization of π−p elastic scattering from 2.22 to 3.50 GeV/c

We have measured the polarization in π^? backward elastic scattering at 2.22, 2.46, 2.71 and 3.50 GeV/c incident momenta, in the u-range?1.0 ≦u≦0.1 (GeV/c)². The experiment used a polarized proton target and detected both pions and protons. We have found large discrepancies between the new data and the result of even the latest phase-shift analysis.     

Characterization of GaAs/AlAs interfacial atomic step structures on a (411)A-oriented substrate by transmission electron microscope

We observed atomic structures of (411)A GaAs/AlAs hetero-interfaces using a transmission electron microscope, and studied the numerical computer simulations of the lattice images for the first time. The observed specimens were GaAs/AlAs multi-layer structures fabricated by molecular beam epitaxy, where the AlAs layers were very thin (0.75-2.1 monolayer). From the hetero-interfacial structures observed in cross-sectional view, it was found that the (411)A atomic step structures were based on Shimomura's model, which has already been proposed in a previous paper. We will discuss the concrete interfacial structure.