Reactions of 57Mn implanted into solid oxygen

The in-beam Mössbauer spectroscopy using a short-lived ⁵⁷Mn (T _1/2=1.5 min) beam was carried out to study the production of the exotic chemical species of ⁵⁷Fe atoms arising from ⁵⁷Mn implanted into solid oxygen. The obtained spectra can be analyzed by four components of doublets at least, which are assigned to be novel Fe species of FeO, Fe(O₂), (O₂)FeO₂, and Fe(O₂)₂, on the basis of ab initio molecular orbital calculations.     

J-PARC E27 Experiment to Search for a Nuclear Kaon Bound State K − pp

In the J-PARC E27 experiment, we search for a K ^? pp bound state via the d(π ⁺, K ⁺) reaction at 1.7 GeV/c at the K1.8 beam line. The binding energy and decay width of the K ^? pp bound state can be obtained in the missing mass measurement with a good energy resolution of 2 MeV/c ². A range counter array (RCA) was constructed to detect the two high-momentum protons from the K ^? pp decay and to reduce the background such as quasi-free hyperon production. Recently, we have carried out a pilot run in June, 2012. The d(π ⁺, K ⁺) missing-mass spectrum has been obtained for the first time. In this report, an overview of the E27 experiment and a preliminary result on this pilot run are presented.     

Production of nuclear polarization of unstable nuclei via polarization transfer reactions

To determine experimental conditions suitable for isotope analysis, we studied the plume dynamics of uranium. A uranium oxide sample was ablated by 2nd harmonic radiation from a Nd:YAG laser at a fluence of 0.5 J/cm². The temporal evolution of the ablation plume was investigated in 800 Pa helium environment. It was found that the observation at 3–5 μs after the ablation at the height of about 2.5 mm are most suited for obtaining higher sensitivity. Using the established conditions, we obtained the limit of detection of the isotope ratio (²³⁵U/²³⁸U) to be 0.01 %. In addition, the limit of detection of elemental abundance of uranium in uranium glass was also evaluated.     

Physics prospects at J-PARC

We have held an inauguration ceremony of the Japan Proton Accelerator Research Complex （JPARC） on July 6,2009,celebrating the completion of its construction.Now,the beam commissioning of the 50 GeV main proton synchrotron is in progress to improve the beam intensity and quality.A lot of important experimental programs in Nuclear Physics are waiting for the beam.In this report,I introduce some examples.     

The quenching of nucleon yields in the nonmesonic weak decay of Λ -hypernuclei and the three-body weak decay process

Recent exclusive coincidence measurements of non-mesonic weak decays (NMWD) reported for the ratio of the partial decay width of neutron-induced-to-proton-induced NMWD, Γ_n/Γ_p , values of 0.45±0.11±0.03 and 0.51±0.13±0.04 for 5lam and ¹² _Λ C , respectively. These observations agree well with the improved theoretical Γ_n/Γ_p ratios which are in the range of 0.3-0.7. It appears that the long-standing discrepancy between the experimental and theoretical values of Γ_n/Γ_p has finally been solved. However, when compared to the results of intra-nuclear cascade (INC) calculations, the observed numbers of both single nucleons and coincident nucleon pairs are strongly quenched. The quenching of the proton yield observed previously has been interpreted as an increase of the Γ_n/Γ_p ratio. On the other hand, significant contributions from the two-nucleon-induced three-body process ΛNN → nNN are predicted. Indeed, the angular correlation of the emitted nucleon pairs in the NMWD of ¹² _Λ C showed not only decay events in back-to-back kinematics, but also events with non-back-to-back kinematics. In this paper we show that the difficulties to extract the correct Γ_n/Γ_p ratio from the proton spectra is related to the three-body weak-interaction process which strongly quenches the nucleon yields.     

SOLVENT EFFECT ON SPHEROIDENE IN NONPOLAR AND POLAR SOLUTIONS AND THE ENVIRONMENT OF SPHEROIDENE IN THE LIGHT-HARVESTING COMPLEXES OF Rhodobacter sphaeroides 2.4.1 AS REVEALED BY THE ENERGY OF THE 1Ag−→1Bu+ ABSORPTION AND THE FREQUENCIES OF THE VIBRONICALLY COUPLED C=C STRETCHING RAMAN LINES IN THE 1Ag− AND 1Bu− STATES

Abstract –The ¹A_g^?→¹B_u⁺ electronic absorption band and the vibronically coupled, C=C stretching Raman lines in the ¹A_g^? and 2¹A_g^? states were recorded for spheroidene free in nonpolar and polar solvents as well as for spheroidene bound to the LH1 and LH2 complexes of Rhodobacter sphaeroides 2.4.1. The ¹B_u⁺ energy exhibited a linear dependence on R(n) = (n² - 1)/(n²+ 2) in both nonpolar and polar solvents; the line for polar solvents had a gentler slope and crossed the line for nonpolar solvents at R(n) = 0.3. The above characteristic of polar solvents was ascribed to the electric field generated by fluctuation of the solvent permanent dipoles; it stabilizes the ¹B_u⁺ energy and reduces the polarizability of the solvent. The vibronically coupled, C=C stretching frequencies in the ¹A_g^? and 2¹A_g^? states [ν(A_g) and [ν(2A_g)] also showed similar dependence on R(n), which is explained in terms of vibronic coupling among the ¹A_g^?, 2¹A_g^? and 3¹A_g^? states. The environment of spheroidene in the LH2 and LH1 complexes was assessed on the basis of the ¹B_u⁺ energy and the ν(A_g) and [ν(2A_g) frequencies: Spheroidene in the LH2 complex is located in an environment with high polarizability, while spheroidene in the LH1 complex is located in an environment with lower polarizability.     

Asymmetric Hydrogenation of Aryl Perfluoroalkyl Ketones Catalyzed by Rhodium(III) Monohydride Complexes Bearing Josiphos Ligands

The asymmetric hydrogenation of 2,2,2-trifluoroacetophenones and aryl perfluoroalkyl ketones was developed using a unique, well-defined chloride-bridged dinuclear rhodium(III) complex bearing Josiphos-type diphosphine ligands. These complexes were prepared from [RhCl(cod)]₂, Josiphos ligands, and hydrochloric acid. As catalyst precursors, they allow for the efficient and enantioselective synthesis (up to 99 % ee) of chiral secondary alcohols with perfluoroalkyl groups. This system does not require an activating base for the hydrogenation of 2,2,2-trifluoroacetophenones. Additionally, the enantioselective C=O hydrogenations of 2-phenyl-3-(haloacetyl)-indoles, a class of privileged structures in medicinal chemistry, is reported for the first time.     

Monohydride-Dichloro Rhodium(III) Complexes with Chiral Diphosphine Ligands as Catalysts for Asymmetric Hydrogenation of Olefinic Substrates

We report full details of the synthesis and characterization of monohydride-dichloro rhodium(III) complexes bearing chiral diphosphine ligands, such as (S)-BINAP, (S)-DM-SEGPHOS, and (S)-DTBM-SEGPHOS, producing cationic triply chloride bridged dinuclear rhodium(III) complexes ( 1 a : (S)-BINAP; 1 b : (S)-DM-SEGPHOS) and a neutral mononuclear monohydride-dichloro rhodium(III) complex ( 1 c : (S)-DTBM-SEGPHOS) in high yield and high purity. Their solid state structure and solution behavior were determined by crystallographic studies as well as full spectral data, including DOSY NMR spectroscopy. Among these three complexes, 1 c has a rigid pocket surrounded by two chloride atoms bound to the rhodium atom together with one tBu group of (S)-DTBM-SEGPHOS for fitting to simple olefins without any coordinating functional groups. Complex 1 c exhibited superior catalytic activity and enantioselectivity for asymmetric hydrogenation of exo-olefins and olefinic substrates. The catalytic activity of 1 c was compared with that of well-demonstrated dihydride species derived in situ from rhodium(I) precursors such as [Rh(cod)Cl]₂ and [Rh(cod)₂]⁺[BF₄]⁻ upon mixing with (S)-DTBM-SEGPHOS under dihydrogen.     

Physics prospects at J-PARC

We have held an inauguration ceremony of the Japan Proton Accelerator Research Complex (J-PARC) on July 6, 2009, celebrating the completion of its construction. Now, the beam commissioning of the 50 GeV main proton synchrotron is in progress to improve the beam intensity and quality. A lot of important experimental programs in Nuclear Physics are waiting for the beam. In this report, I introduce some examples.