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Kumar, V.*; Chapman, R.*; O'Donnell, D.*; Ollier, J.*; Orlandi, R.; Smith, J. F.*; Spohr, K.-M.*; Torres, D. A.*; 他13名*
Physical Review C, 108(4), p.044313_1 - 044313_19, 2023/10
The nuclear structure of neutron-rich niobium isotopes Nb were studied at the Legnaro National Laboratories using -ray spectroscopy. The isotopes were produced in two different experiments, either using multi-nucleon transfer reactions of Zr 530-MeV beam onto a Sn target, or via fusion-fission of S on Yb. The level schemes of these isotopes were extended respectively up to excitation energies of 4545, 5409, and 3814 keV. The structure of the low-lying states in these isotopes was interpreted and discussed in the context of shell-model calculations. In particular, for the Nb isotope (=41, =58), the results indicate the presence of shape-coexistence at low-energies, which was observed for the first time in this isotope.
Kozulin, E. M.*; Knyazheva, G. N.*; Itkis, I. M.*; Itkis, M. G.*; Mukhamejanov, Y. S.*; Bogachev, A. A.*; Novikov, K. V.*; Kirakosyan, V. V.*; Kumar, D.*; Banerjee, T.*; et al.
Physical Review C, 105(1), p.014607_1 - 014607_12, 2022/01
被引用回数:6 パーセンタイル:95.95(Physics, Nuclear)Asymmetric fission in the neutron-deficient Hg region was first observed about 10 years ago at ISOLDE, and caused a revision of the current understanding of fission in this region. In this work, the fission of Hg and Pd were studied using the time-of-flight spectrometer CORSET at the Flerov Laboratory in Dubna. The observed fission fragments mass distributions of the different isotopes suggest the presence of four concurrent fission modes, one symmetric and three asymmetric fission modes. The asymmetric modes differ in the total kinetic energies and fragment mass splits. These results point out the existence of a well deformed proton shell at =36 and a less deformed proton shell at =46.
Bogachev, A. A.*; Kozulin, E. M.*; Knyazheva, G. N.*; Itkis, I. M.*; Itkis, M. G.*; Novikov, K. V.*; Kumar, D.*; Banerjee, T.*; Diatlov, I. N.*; Cheralu, M.*; et al.
Physical Review C, 104(2), p.024623_1 - 024623_11, 2021/08
被引用回数:10 パーセンタイル:92.98(Physics, Nuclear)Hg及びPb核の非対称及び対称核分裂モードの研究のため、Ar + Sm,Ca + Sm反応で生成したHg及びPbの質量-エネルギー分布の測定を行った。クーロン障壁エネルギー近傍のエネルギーにおいて、質量-エネルギー分布は二重アーム飛行時間型スペクトロメータCORSETを用いて測定し、以前に測定したPb同位体と比較した。結論として、HgとPb核の非対称核分裂の研究特性はZ36では変形した陽子殻の存在を、Z46では変形しない陽子殻の存在を指摘した。
Kumar, S.*; Saha, D.*; 高田 慎一; Aswal, V. K.*; 瀬戸 秀紀
Applied Physics Letters, 118(15), p.153701_1 - 153701_7, 2021/04
We report the pathways to suppress or enhance the protein adsorption on nanoparticles and thereby control the stability of the nanoparticle-protein complexes with the help of selective additives. This has been achieved by tuning the electrostatic interaction between the nanoparticles and proteins, in the presence of surfactant and multivalent counterions. The preferential binding of the proteins with the surfactant and multivalent ions induced charge reversibility of nanoparticles can lead to adsorption of an otherwise non-adsorbing protein and vice versa. The findings are demonstrated for anionic silica nanoparticles and two globular proteins [lysozyme (cationic) and bovine serum albumin (BSA) (anionic)] as model systems, in the presence of two ionic surfactants [anionic sodium dodecyl sulfate (SDS) and cationic dodecyltrimethylammonium bromide (DTAB)], and ZrCl as multivalent salt.
Singh, H.*; Ray, D.*; Kumar, S.*; 高田 慎一; Aswal, V. K.*; 瀬戸 秀紀
Physical Review E, 102(6), p.062601_1 - 062601_11, 2020/12
The interaction of nanoparticles with surfactants is extensively used in a wide range of applications from enhancing colloidal stability to phase separation processes as well as in the synthesis of noble functional materials. The interaction is highly specific depending on the charged nature of the surfactant. In the case of nonionic surfactants, the micelles adsorb on the surface of nanoparticles. The adsorption of nonionic surfactant C12E10 as a function of surfactant concentration for two different sizes of anionic silica nanoparticles (16 and 27 nm) has been examined using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The study on different-sized nanoparticles shows that the lower curvature enhances the packing fraction whereas the loss of surface-to-volume ratio suppresses the fraction of adsorbed micelles with the increase in the nanoparticle size.
Shikin, A. M.*; Estyunin, D. A.*; Klimovskikh, I. I.*; Filnov, S. O.*; Kumar, S.*; Schwier, E. F.*; 宮本 幸治*; 奥田 太一*; 木村 昭夫*; 黒田 健太*; et al.
Scientific Reports (Internet), 10, p.13226_1 - 13226_13, 2020/08
被引用回数:48 パーセンタイル:96.27(Multidisciplinary Sciences)Modification of the gap at the Dirac point (DP) in axion antiferromagnetic topological insulator MnBiTe and its electronic and spin structure have been studied by angle- and spin-resolved photoemission spectroscopy (ARPES) under laser excitation at various temperatures, light polarizations and photon energies. We have distinguished both large and reduced gaps at the DP in the ARPES dispersions, which remain open above the Nel temperature of = 24.5 K. We propose that the gap above remains open due to a short-range magnetic field generated by chiral spin fluctuations. Spin-resolved ARPES, XMCD and circular dichroism ARPES measurements show a surface ferromagnetic ordering for the large gap sample and apparently significantly reduced effective magnetic moment for the reduced gap sample.
Torres, D. A.*; Chapman, R.*; Kumar, V.*; Hadinia, B.*; Hodsdon, A.*; Labiche, M.*; Liang, X.*; O'Donnell, D.*; Ollier, J.*; Orlandi, R.; et al.
European Physical Journal A, 55(9), p.158_1 - 158_21, 2019/09
被引用回数:0 パーセンタイル:0.02(Physics, Nuclear)Excited states of the rubidium isotopes Rb were studied at the INFN Legnaro National Laboratory. Measurements of the -ray of nuclei produced in binary reactions from the interaction of a beam of 530 MeV Zr ions with a Sn target were complemented by studies of the -rays from nuclei produced in the interaction of a beam of 230 MeV S ions with a thick Yb target. The structure of the yrast states of Rb is discussed within the context of spherical shell-model and cranked Nilsson-Strutinsky calculations.
Shikin, A. M.*; Estyunin, D. A.*; Surnin, Yu. I.*; Koroleva, A. V.*; Shevchenko, E. V.*; Kokh, K. A.*; Tereshchenko, O. E.*; Kumar, S.*; Schwier, E. F.*; 島田 賢也*; et al.
Scientific Reports (Internet), 9(1), p.4813_1 - 4813_17, 2019/03
被引用回数:19 パーセンタイル:71.98(Multidisciplinary Sciences)A new kind of magnetically-doped antiferromagnetic (AFM) topological insulators (TIs), BiGdSbTe, has been studied by angle-resolved photoemission, superconducting magnetometry (SQUID) and X-ray magnetic circular dichroism (XMCD). It has been shown that this TI is characterized by the Dirac gap at the Fermi level. In the paramagnetic phase, a surface magnetic layer is supposed to develop, where the coupling between the Gd magnetic moments is mediated by the topological surface states (TSSs). This assumption can be confirmed by opening a gap at the Dirac point indicated by the surface-sensitive ARPES, a weak hysteresis loop measured by SQUID, the XMCD showing a surface magnetic moment and the temperature dependence of electrical resistance demonstrating a mid-gap semiconducting behavior, which correlates with the temperature dependence of the surface magnetization and confirms the conclusion that only TSSs are located at the Fermi level.
Gu, Y. J.*; Klimo, O.*; Kumar, D.*; Liu, Y.*; Singh, S. K.*; Esirkepov, T. Z.; Bulanov, S. V.; Weber, S.*; Korn, G.*
Physical Review E, 93(1), p.013203_1 - 013203_6, 2016/01
被引用回数:24 パーセンタイル:86.99(Physics, Fluids & Plasmas)The magnetic quadrupole structure formation during the interaction of two ultrashort high power laser pulses with a collisionless plasma is demonstrated with 2.5-dimensional particle-in-cell simulations. The subsequent expansion of the quadrupole is accompanied by magnetic-field annihilation in the ultrarelativistic regime, when the magnetic field cannot be sustained by the plasma current.
Gu, Y. J.*; Klimo, O.*; Kumar, D.*; Bulanov, S. V.; Esirkepov, T. Z.; Weber, S.*; Korn, G.*
Physics of Plasmas, 22(10), p.103113_1 - 103113_9, 2015/10
被引用回数:8 パーセンタイル:41.4(Physics, Fluids & Plasmas)The magnetic field generated by the laser pulses annihilates in a current sheet formed between the pulses. Magnetic field energy is converted to an inductive longitudinal electric field, which efficiently accelerates the electrons of the current sheet. This new regime of collision less relativistic magnetic field annihilation with a timescale of tens of femtoseconds can be extended to near-critical and overdense plasma with the ultra-high intensity femtosecond laser pulses.
Gaffney, L. P.*; Robinson, A. P.*; Jenkins, D. G.*; Andreyev, A. N.; Bender, M.*; Blazhev, A.*; Bree, N.*; Bruyneel, B.*; Butler, P.*; Cocolios, T. E.*; et al.
Physical Review C, 91(6), p.064313_1 - 064313_11, 2015/06
被引用回数:8 パーセンタイル:51(Physics, Nuclear)Radioactive ion beams of Rn were studied by means of low-energy Coulomb excitation at REX-ISOLDE, CERN. The electric-quadrupole (E2) matrix elements connecting the first excited 2 to the ground state of these nuclei was extracted, which permits to determine the collectivity of these isotopes, which in both cases is deduced to be weak, as expected from the low-lying level-energy scheme. Comparisons were also made with beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.
Kumar, M. V.*; 栗林 一彦*; 長汐 晃輔*; 石川 毅彦*; 岡田 純平*; Yu, J.*; 依田 眞一*; 片山 芳則
Applied Physics Letters, 100(19), p.191905_1 - 191905_4, 2012/05
被引用回数:2 パーセンタイル:8.97(Physics, Applied)制御された酸素分圧o下での過冷却LuFeO融体から形成される準安定相のその場観察による同定を、放射光光源におけるX線回折測定によって行った。1kHzの高速イメージングシステムによって、oが110PaでのLuFeO及びLuFeO相の単一リカレッセンス中のそれぞれの相の生成と成長を実時間で観察することができた。LuFeO系で観察された準安定相の回折パターンはLu-Fe-O系で報告されている準安定及び安定相のものと矛盾しない。