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論文

Angular correlation of the two gamma rays produced in the thermal neutron capture on gadolinium-155 and gadolinium-157

Goux, P.*; Glessgen, F.*; Gazzola, E.*; Singh Reen, M.*; Focillon, W.*; Gonin, M.*; 田中 智之*; 萩原 開人*; Ali, A.*; 須藤 高志*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2023(6), p.063H01_1 - 063H01_15, 2023/06

 被引用回数:0 パーセンタイル:0.01(Physics, Multidisciplinary)

We investigated the angular correlation of two $$gamma$$-rays emitted in neutron capture at the Materials and Life Science Experimental Facility of J-PARC. The 14 Ge crystals in a cluster detector and one coaxial Ge crystal were employed. We obtained angular correlation functions for two $$gamma$$-rays emerging in the electromagnetic transitions of the capture reactions on $$^{155}$$Gd and $$^{157}$$Gd. We found mild angular correlations for the strong, but rare transitions from the resonance state to two excited levels with known spin and parities. In contrast, angular correlations was negligibly small for arbitrary pairs of two $$gamma$$-rays produced in the majority of transitions in continuum states.

論文

Improved measurement of the $$0_2^+rightarrow0_1^+$$ $$E$$0 transition strength for $$^{72}$$Se using the SPICE spectrometer

Smallcombe, J.; Garnsworthy, A. B.*; Korten, W.*; Singh, P.*; Ali, F. A.*; Andreoiu, C.*; Ansari, S.*; Ball, G. C.*; Barton, C. J.*; Bhattacharjee, S. S.*; et al.

Physical Review C, 106(1), p.014312_1 - 014312_9, 2022/07

 被引用回数:3 パーセンタイル:66.85(Physics, Nuclear)

The selenium isotopes lie at the heart of a tumultuous region of the nuclear chart where shape coexistence effects grapple with neutron-proton pairing correlations, triaxiality, and the impending proton dripline. In this work a study of $$^{72}$$Se by internal conversion electron and $$gamma$$-ray spectroscopy was undertaken with the SPICE and TIGRESS arrays. New measurements of the branching ratio and lifetime of the $$0_2^+$$ state were performed yielding a determination of $$rho^2(E0; 0_2^+{rightarrow}0_1^+)=29(3)$$ milliunits. Two state mixing calculations were performed that highlighted the importance of interpretation of such $$E0$$ strength values in the context of shape-coexistence.

論文

Groundwater $$Elusimicrobia$$ are metabolically diverse compared to gut microbiome $$Elusimicrobia$$ and some have a novel nitrogenase paralog

M$'e$heust, R.*; Castelle, C. J.*; Matheus Carnevali, P. B.*; Farag, I. F.*; He, C.*; Chen, L.-X.*; 天野 由記; Hug, L. A.*; Banfield, J. F.*

ISME Journal, 14(12), p.2907 - 2922, 2020/12

 被引用回数:39 パーセンタイル:94.42(Ecology)

We reconstructed 94 draft-quality, non-redundant genomes from diverse animal-associated and natural environments. Genomes group into 12 clades, 10 of which previously lacked reference genomes. Groundwater-associated $$Elusimicrobia$$ are predicted to be capable of heterotrophic or autotrophic lifestyles, reliant on oxygen or nitrate/nitrite-dependent respiration of fatty acids, or a variety of organic compounds and Rnf-dependent acetogenesis with hydrogen and carbon dioxide as the substrates. Genomes from two clades of groundwater-associated $$Elusimicrobia$$ often encode a new homologous group of nitrogenase-like proteins that co-occur with an extensive suite of radical SAM-based proteins. We identified similar genomic loci in genomes of bacteria from the Gracilibacteria and Myxococcus phyla and predict that the gene clusters reduce a tetrapyrrole, possibly to form a novel cofactor. The animal-associated $$Elusimicrobia$$ clades nest phylogenetically within two groundwater-associated clades. Thus, we propose an evolutionary trajectory in which some $$Elusimicrobia$$ adapted to animal-associated lifestyles from groundwater-associated species via genome reduction.

論文

Population of a low-spin positive-parity band from high-spin intruder states in $$^{177}$$Au; The Two-state mixing effect

Venhart, M.*; Balogh, M.*; Herz$'a$$v{n}$, A.*; Wood, J. L.*; Ali, F. A.*; Joss, D. T.*; Andreyev, A. N.; Auranen, K.*; Carroll, R. J.*; Drummond, M. C.*; et al.

Physics Letters B, 806, p.135488_1 - 135488_6, 2020/07

 被引用回数:6 パーセンタイル:59.56(Astronomy & Astrophysics)

The extremely neutron-deficient isotopes $$^{177,179}$$Au were studied by means of in-beam $$gamma$$-ray spectroscopy. Specific tagging techniques, $$alpha$$-decay tagging in $$^{177}$$Au and isomer tagging in $$^{179}$$Au, were used for these studies. Feeding of positive-parity, nearly spherical states, which are associated with 2$$d_{3/2}$$ and 3$$s_{1/2}$$ proton-hole configurations, from the 1$$i_{13/2}$$ proton-intruder configuration was observed in $$^{177}$$Au. Such a decay path has no precedent in odd-Au isotopes and it is explained by the effect of mixing of wave functions of the initial state.

論文

Clades of huge phages from across Earth's ecosystems

Al-Shayeb, B.*; Sachdeva, R.*; Chen, L.-X.*; Ward, F.*; Munk, P.*; Devoto, A.*; Castelle, C. J.*; Olm, M. R.*; Bouma-Gregson, K.*; 天野 由記; et al.

Nature, 578(7795), p.425 - 431, 2020/02

 被引用回数:220 パーセンタイル:99.5(Multidisciplinary Sciences)

Phage typically have small genomes and depend on their bacterial hosts for replication. We generated metagenomic datasets from many diverse ecosystems and reconstructed hundreds of huge phage genomes, between 200 kbp and 716 kbp in length. Thirty four genomes were manually curated to completion, including the largest phage genomes yet reported. Expanded genetic repertoires include diverse and new CRISPR-Cas systems, tRNAs, tRNA synthetases, tRNA modification enzymes, initiation and elongation factors and ribosomal proteins. Phage CRISPR have the capacity to silence host transcription factors and translational genes, potentially as part of a larger interaction network that intercepts translation to redirect biosynthesis to phage-encoded functions. Some phage repurpose bacterial systems for phage-defense to eliminate competing phage. We phylogenetically define seven major clades of huge phage from human and other animal microbiomes, oceans, lakes, sediments, soils and the built environment. We conclude that large gene inventories reflect a conserved biological strategy, observed across a broad bacterial host range and resulting in the distribution of huge phage across Earth's ecosystems.

論文

$$alpha$$-decay properties of $$^{200,202}$$Fr

Ghys, L.*; Andreyev, A. N.; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Capponi, L.*; Cocolios, T. E.*; Cubiss, J.*; Derkx, X.*; et al.

Physical Review C, 100(5), p.054310_1 - 054310_13, 2019/11

 被引用回数:12 パーセンタイル:77.09(Physics, Nuclear)

The aim of this work was to investigate the $$alpha$$-decay properties of $$^{200,202}$$Fr and daughter products. Neutron-deficient francium nuclei are produced at ISOLDE-CERN bombarding a UCx target with 1.4 GeV protons. Due to the very high statistics and the high beam purity, improved decay data for $$^{202}$$Fr and its daughters were obtained. The observation of crossover transitions positioned the isomeric high-spin level of $$^{198}$$At at an excitation energy of 265(3) keV. Half-life values of 4.47(5) s and 1.28(10) s were extracted for the ground state and isomeric state of $$^{198}$$At and 52(3) ms for the ground-state decay of $$^{200}$$Fr.

論文

Low-velocity transient-field technique with radioactive ion beams; $$g$$ factor of the first excited $$2^+$$ state in $$^{72}$$Zn

Illana, A.*; Jungclaus, A.*; Orlandi, R.; Perea, A.*; Bauer, C.*; Briz, J. A.*; Egido, J. L.*; Gernh$"a$user, R.*; Leske, J.*; M$"u$cher, D.*; et al.

Physical Review C, 89(5), p.054316_1 - 054316_11, 2014/05

 被引用回数:11 パーセンタイル:60.34(Physics, Nuclear)

The $$g$$ factor of the first excited state in $$^{72}$$Zn was measured using the transient-field technique in combination with Coulomb excitation. The experiment was ran at REX-ISOLDE, CERN, and the $$gamma$$-ray perturbed angular correlations were measured using 4 triple Germanium clusters of the Miniball array. The experimental result $$g$$(2$$_1^{+}$$) = +0.47(14) is significant to establish the structure of the Zn isotopes near N=40. Comparison with shell-model calculations reveal that to reproduce the measured energies and B(E2) of the Zn isotopes around N=40, both the proton excitations from the $$f_{7/2}$$ orbit and neutron excitations into the $$g_{9/2}$$ and $$d_{5/2}$$ orbits are essential. Furthermore, beyond-mean-field calculations reveal the need to include the triaxial degree of freedom.

論文

Measurement of the first ionization potential of astatine by laser ionization spectroscopy

Rothe, S.*; Andreyev, A. N.*; Antalic, S.*; Borschevsky, A.*; Capponi, L.*; Cocolios, T. E.*; De Witte, H.*; Eliav, E.*; Fedorov, D. V.*; Fedosseev, V. N.*; et al.

Nature Communications (Internet), 4, p.1835_1 - 1835_6, 2013/05

 被引用回数:83 パーセンタイル:94.59(Multidisciplinary Sciences)

The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of smallest quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential (IP). Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states allowed the deduction of the IP of the astatine atom for the first time. New ab initio calculations were performed to support the experimental result. The measured value of IP(At) serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of super-heavy element 117, the heaviest homologue of astatine.

論文

Spins and magnetic moments of $$^{49}$$K and $$^{51}$$K; Establishing the 1/2$$^+$$ and 3/2$$^+$$ level ordering beyond $$N$$ = 28

Papuga, J.*; Bissell, M. L.*; Kreim, K.*; Blaum, K.*; Brown, B. A.*; De Rydt, M.*; Garcia Ruiz, R. F.*; Heylen, H.*; Kowalska, M.*; Neugart, R.*; et al.

Physical Review Letters, 110(17), p.172503_1 - 172503_5, 2013/04

 被引用回数:35 パーセンタイル:82.14(Physics, Multidisciplinary)

CERNのISOLDEにて、中性子過剰のカリウム同位体を生成,分離し、レーザー核分光によって$$^{49}$$K及び$$^{51}$$Kの基底状態のスピン及び磁気モーメントを初めて測定した。カリウム同位体は陽子数が19であるため、低励起状態に陽子の一空孔状態が観測されると考えられ、基底状態の量子数から陽子の殻構造の情報が引き出される。これまで、中性子数28の同位体までの基底状態が測定されており、中性子数20から28まで変化させると、基底状態が3/2$$^+$$から1/2$$^+$$へと変化するという準位の逆転現象が知られていた。今回の実験で、$$^{49}$$Kの基底状態は1/2$$^+$$, $$^{51}$$Kの基底状態は3/2$$^+$$であることが確定し、陽子準位が再逆転することを観測した。この再逆転現象は、標準的なポテンシャル模型では理解されず、殻模型計算によって、有効相互作用が殻構造の変化をもたらすのに本質的であることを明らかにした。

論文

Local thermal expansion and the C-C stretch vibration of the dicarbon antisite in 4H SiC

Devaty, R. P.*; Yan, F.*; Choyke, W. J.*; Gali, A.*; 木本 恒暢*; 大島 武

Materials Science Forum, 717-720, p.263 - 266, 2012/05

 被引用回数:1 パーセンタイル:54.7(Materials Science, Multidisciplinary)

The Carbon-Carbon (C-C) stretch vibration associated with the dicarbon antisite in 4H Silicon Carbide (SiC) has been observed from up to the fifth harmonic in the low temperature photoluminescence spectrum. By the fitting to the obtained data using the Morse potential, we can obtain the reasonable anharmonicity. We also combined experimental results, the analytically tractable Morse potential, and results obtained from first principles calculations in order to estimate the thermal expansion coefficient of the C-C bond. This local thermal expansion coefficient is considerably smaller than the linear thermal expansion coefficient of bulk 4H SiC, in striking contrast with the recent result obtained from the nitrogen-vacancy center in diamond that the local thermal expansion coefficientis larger than the bulk value.

論文

Anharmonic vibrations of the dicarbon antisite defect in 4H-SiC

Yan, F.*; Devaty, R. P.*; Choyke, W. J.*; Gali, A.*; 木本 恒暢*; 大島 武; Pensl, G.*

Applied Physics Letters, 100(13), p.132107_1 - 132107_3, 2012/03

 被引用回数:3 パーセンタイル:13.53(Physics, Applied)

Dicarbon antisite defects were introduced into 4H Silicon Carbide (SiC) by either electron irradiation or ion implantation (H or He) and subsequent annealing between 700 and 1700 $$^{circ}$$C for 30 min in Ar. As a result of low temperature photoluminescence at 2 K, the no-phonon lines from the dicarbon antisite defect center were detected with their phonon replicas. The stretch frequencies of the defect with up to the fifth harmonic were also observed. The Morse potential model accounts for the anharmonicity quite well and gives a very good prediction of the vibration energies up to the fifth harmonic at an error within 1%. The observed anharmonicity can be explained in terms of the model of a dicarbon antisite defect along with its four nearest neighboring carbon atoms using first principles calculations.

論文

New lines and issues associated with deep defect spectra in electron, proton and $$^{4}$$He ion irradiated 4H SiC

Yan, F.*; Devaty, R. P.*; Choyke, W. J.*; 木本 恒暢*; 大島 武; Pensl, G.*; Gali, A.*

Materials Science Forum, 645-648, p.411 - 414, 2010/00

耐放射線性が期待される炭化ケイ素(SiC)半導体へ電子,陽子又は$$^{4}$$Heイオン照射を行い、発生する欠陥を低温でのフォトルミネッセンス(LTPL)測定により評価した。照射後、7KでのLTPL測定を行ったところ、2.48から2.62eV範囲に照射欠陥に起因する複数の新たな発光ピークが観察された。これら発光ピークの熱処理による挙動を調べたところ、すべてのピークが同様な振る舞いを示し、1300から1400$$^{circ}$$Cの熱処理によりすべてのラインが消滅することが判明した。このことより、これらのピークは同一の欠陥に起因することが明らかとなった。さらに、理論計算による解析を行ったところ、SiCのシリコン格子位置を占有した炭素原子(カーボンアンチサイト)が二つ並んだダイカーボンアンチサイトがこの発光ピークの原因であることが判明した。

論文

High-resolution water window X-ray imaging of in vivo cells and their products using LiF crystal detectors

Bonfigli, F.*; Faenov, A. Y.; Flora, F.*; Francucci, M.*; Gaudio, P.*; Lai, A.*; Martellucci, S.*; Montereali, R. M.*; Pikuz, T.*; Reale, L.*; et al.

Microscopy Research and Technique, 71(1), p.35 - 41, 2008/01

 被引用回数:26 パーセンタイル:71.86(Anatomy & Morphology)

High contrast imaging of in vivo cells with submicron spatial resolution was obtained with a contact water window X-ray microscopy technique using a point-like, laser-plasma produced water-window X-ray radiation source and LiF crystals as detectors. The powerful performance of LiF crystals allowed to detect the exudates of Chlorella cells in their living medium and their spatial distribution in situ, without any special sample preparation

口頭

Study of $$^{70,72}$$Se nuclear shapes with SPICE and TIGRESS

Smallcombe, J.; Garnsworthy, A. B.*; Korten, W.*; Singh, P.*; Ali, F. A.*; Andreoiu, C.*; Ansari, S.*; Ball, G. C.*; Barton, C. J.*; Bhattacharjee, S. S.*; et al.

no journal, , 

The phenomenon of shape coexistence is prevalent in the Z$$sim$$34 region, with isotopes of neutron-deficient even Ge, Se and Kr each exhibiting the characteristic low-lying coexisting 0+ bands which display quadrupole deformation different to that of the ground states. In the selenium isotopes, $$^{72-78}$$Se seem to show a prolate ground structure with shape coexisting oblate excitation, while in $$^{68}$$Se the oblate structure appears to have become the ground state. The exact nature of the low-lying structure $$^{70}$$Se and any shape coexistence remains uncertain. Combining the Spectrometer for Internal Conversion Electrons (SPICE) with the TIGRESS HPGe Array, a full electron and gamma-ray experimental study of $$^{70}$$Se, $$^{72}$$Se was undertaken at the TRIUMF ISAC-II facility to unveil the low-lying structure of these nuclei. Details of the device and experiment will be presented, alongside the experimental results and possible structural interpretations for both isotopes.

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