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The ground-state configuration of the N = 157 nucleus 259No has been identified through ɑ-ɣ coincidence and ɑ-singles measurements. Three ɣ transitions were observed for the first time in the a decay of 259No, and its decay scheme was established. The neutron 9/2+[615] configuration was assigned to the ground state of 259No as well as to the 231.4 keV level in 255Fm. Ground-state deformations and neutron single-particle energies in Z = 102 isotopes were calculated with the macroscopic-microscopic model. The 9/2+[615] orbital was calculated to be the highest among the five orbitals between the N = 152 and 162 deformed shell gaps, which is consistent with the experimental one-quasiparticle energies in N = 153 and 155 isotones, but is inconsistent with the present experimental result of the 9/2+[615] ground state at N = 157. To reproduce the 9/2+[615] ground state at N = 157, the order of the neutron orbitals should be different between the N = 153 and 157 isotones. [ABSTRACT FROM AUTHOR]

Excited states in 251Fm populated via the a decay of 255No are studied in detail through α-γ coincidence and a fine-structure measurements. Five excited states reported previously in 251Fm are firmly established through the α-γ coincidence measurement, and rotational bands built on one-quasiparticle states are newly established through the a fine-structure measurement. Spin-parities and neutron configurations of the excited states in 251Fm as well as the ground state of 255No are definitely identified on the basis of deduced internal conversion coefficients, lifetimes of γ transitions, rotational-band energies built on one-quasiparticle states, and hindrance factors of a transitions. It is found that the excitation energy of the 1/2+[620] state in N=151 isotones increases with the atomic number, especially at Z⩾100, while that of the 1/2+[631] state decreases at Z=100. Ground-state deformations and energies of neutron one-quasiparticle states in the N=151 isotones are calculated using a macroscopic-microscopic model, and the energy systematics of the one-quasiparticle states in the isotones are discussed in terms of the evolution of nuclear deformation involving the hexadecapole (β4) and hexacontatetrapole (β6) deformations. [ABSTRACT FROM AUTHOR]

The first elastic electron scattering has been successfully performed at the self-confining radioactive-isotope ion target (SCRIT) facility, the world's first electron scattering facility for SCRIT technique achieved high luminosity (over 1027 cm-2s-1, sufficient for determining the nuclear shape) with only 108 target ions. While 132Xe used in this time as a target is a stable isotope, the charge density distribution was first extracted from the momentum transfer distributions of the scattered electrons by comparing the results with those calculated by a phase shift calculation. [ABSTRACT FROM AUTHOR]

Two isomeric states of 265Sg, i.e., 265Sga and 265Sgb, proposed in Ch. E. Diillmann and A. Tiirler [Phys. Rev. C 77, 064320 (2008)] were produced in the 248Cm(22Ne,5n)265Sg reaction. Decay properties of 265Sga,b were investigated with a rotating-wheel apparatus for &agr; and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated &agr;-&agr;(-&agr;) and &agr;-SF decay chains, 18 and 24 events were assigned to 265Sga and 265Sgb, respectively. The half-life T1/2 and &agr;-particle energy E&agr; of 265Sg&agr; were measured to be 8.5+2.6-1.6 s and 8.84 ± 0.05 MeV, respectively, and those of 265Sgb were 14.4+3.7-2.5 s and 8.69 ± 0.05 MeV. As a daughter product of 265Sga,b the decay properties of the 3-s isomeric state in 26lRf, i.e., 26lRfb were also derived: T1/2 = 2.6+0.7-0.5 s, E&agr; =8.51 ± 0.06 MeV, and SF branch bSF = 0.82 ± 0.09. These results confirm and refine the decay pattern suggested for the decay chain 269Hs → 265Sga,b → 261Rfa,b → 257No → in Düllmann and Türler. The production cross sections for 265Sga and 265Sgb were determined to be 180+80-60 and 200+60-50 at 117.8 MeV, respectively, and they are discussed by comparing with the literature data as well as the theoretical prediction. [ABSTRACT FROM AUTHOR]

Five new 2+ levels have been established in the semimagic 210Po nucleus from a 208Pb(12C,10Be) two-proton transfer experiment, performed at energies close to the Coulomb barrier at JAEA Tokai. A setup combining Ge, LaBr3, and Si telescopes was used to detect both in-beam γ rays and ejectile residues. The new 2+ states have been established by means of the transitions toward the 0+ ground state which are present in the γ spectra produced by properly selecting the excitation energy in 210Po after kinematical reconstruction. (f7/2)², h9/2⊗f5/2, (i13/2)², f7/2⊗p3/2, and f7/2⊗f5/2 two-proton configurations are assigned to these states. In addition, a new 3-level has also been established in this nucleus, very likely originating from the f7/2⊗i13/2 configuration. Shell-model calculations strongly support these assignments. [ABSTRACT FROM AUTHOR]

The validity of the multinucleon transfer (MNT) approach for deduction of fission barrier heights was investigated in an experiment carried out at the JAEA tandem accelerator facility. By using the 18O + 237Np reaction, fission barrier heights were inferred from fission probabilities of the nuclei 239Np and 239,240Pu produced in the 2n and pn/p2n transfer channels, respectively. The deduced values of fission barriers agree well with the literature data, thus demonstrating the potential of the MNT reactions for obtaining fission-barrier data for nuclei not accessible for fission studies via neutron- or light charged particle-induced reactions. [ABSTRACT FROM AUTHOR]

Fission-fragment mass distributions were measured for 237-240U, 239-242Np, and 241-244Pu populated in the excitation-energy range from 10 to 60 MeV by multinucleon transfer channels in the reaction 18O+238U at the Japan Atomic Energy Agency tandem facility. Among them, the data for 240U and 240,241,242Np were observed for the first time. It was found that the mass distributions for all the studied nuclides maintain a double-humped shape up to the highest measured energy in contrast to expectations of predominantly symmetric fission due to the washing out of nuclear shell effects. From a comparison with the dynamical calculation based on the fluctuation-dissipation model, this behavior of the mass distributions was unambiguously attributed to the effect of multichance fission. [ABSTRACT FROM AUTHOR]

We successfully performed electron scattering off unstable nuclei which were produced online from the photofission of uranium. The target ^{137}Cs ions were trapped with a new target-forming technique that makes a high-density stationary target from a small number of ions by confining them in an electron storage ring. After developments of target generation and transportation systems and the beam stacking method to increase the ion beam intensity up to approximately 2×10^{7} ions per pulse beam, an average luminosity of 0.9×10^{26}  cm^{-2} s^{-1} was achieved for ^{137}Cs. The obtained angular distribution of elastically scattered electrons is consistent with a calculation. This success marks the realization of the anticipated femtoscope which clarifies the structures of exotic and short-lived unstable nuclei.

We observed the atomic 1s and 2p states of π^{-} bound to ^{121}Sn nuclei as distinct peak structures in the missing mass spectra of the ^{122}Sn(d,^{3}He) nuclear reaction. A very intense deuteron beam and a spectrometer with a large angular acceptance let us achieve a potential of discovery, which includes the capability of determining the angle-dependent cross sections with high statistics. The 2p state in a Sn nucleus was observed for the first time. The binding energies and widths of the pionic states are determined and found to be consistent with previous experimental results of other Sn isotopes. The spectrum is measured at finite reaction angles for the first time. The formation cross sections at the reaction angles between 0° and 2° are determined. The observed reaction-angle dependence of each state is reproduced by theoretical calculations. However, the quantitative comparison with our high-precision data reveals a significant discrepancy between the measured and calculated formation cross sections of the pionic 1s state.

The first elastic electron scattering has been successfully performed at the self-confining radioactive-isotope ion target (SCRIT) facility, the world's first electron scattering facility for SCRIT technique achieved high luminosity (over 10^{27}  cm^{-2} s^{-1}, sufficient for determining the nuclear shape) with only 10^{8} target ions. While ^{132}Xe used in this time as a target is a stable isotope, the charge density distribution was first extracted from the momentum transfer distributions of the scattered electrons by comparing the results with those calculated by a phase shift calculation.

At the Mainz Microtron MAMI, the first high-resolution pion spectroscopy from decays of strange systems was performed by electron scattering off a (9)Be target in order to study the Λ binding energy of light hypernuclei. Positively charged kaons were detected by a short-orbit spectrometer with a broad momentum acceptance at 0° forward angles with respect to the beam, efficiently tagging the production of strangeness in the target nucleus. Coincidentally, negatively charged decay pions were detected by two independent high-resolution spectrometers. About 10(3) pionic weak decays of hyperfragments and hyperons were observed. The pion momentum distribution shows a monochromatic peak at pπ≈133  MeV/c, corresponding to the unique signature for the two-body decay of hyperhydrogen Λ(4)H→(4)He+π(-), stopped inside the target. Its Λ binding energy was determined to be BΛ=2.12±0.01  (stat)±0.09  (syst)MeV with respect to the (3)H+Λ mass.

An experiment with a newly developed high-resolution kaon spectrometer and a scattered electron spectrometer with a novel configuration was performed in Hall C at Jefferson Lab. The ground state of a neutron-rich hypernucleus, (Λ)(7)He, was observed for the first time with the (e, e'K+) reaction with an energy resolution of ~0.6 MeV. This resolution is the best reported to date for hypernuclear reaction spectroscopy. The (Λ)(7)He binding energy supplies the last missing information of the A = 7, T = 1 hypernuclear isotriplet, providing a new input for the charge symmetry breaking effect of the ΛN potential.

We have measured the branching ratio of the three-body process in the nonmesonic weak decay of Lambda12C to be 0.29+/-0.13. This result was obtained by reproducing the nucleon and the nucleon pair yields introducing a measured final state interaction. At the same time, we have determined the absolute decay widths, Gamma(n) and Gamma(p), along with Gamma2N, whose relative ratio has been a long-standing puzzle. Including the three-body process, we have successfully reproduced the nucleon energy distribution, the coincidence two-nucleon angular correlation, and the momentum sum distribution simultaneously.

We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay of lambda(5)He formed via the 6Li(pi+, K+) reaction. The energies of the two nucleons and the pair number distributions in the opening angle between them were measured. In both np and nn pairs, we observed a clean back-to-back correlation coming from the two-body weak reactions of lambda p --> np and lambda n --> nn, respectively. The ratio of the nucleon pair numbers was N(nn)/N(np) = 0.45 +/- 0.11(stat) +/- 0.03(syst) in the kinematic region of cos theta(NN) < -0.8. Since each decay mode was exclusively detected, the measured ratio should be close to the ratio of gamma(lambda p --> np)/gamma(lambda n --> nn). The ratio is consistent with recent theoretical calculations based on the heavy meson and/or direct-quark exchange picture.

alpha-gamma and alpha-electron coincidence spectroscopy for a short-lived heavy actinide nucleus (257)No (T(1/2) = 24.5 s) has been performed using a gas-jet transport system and an on-line isotope separator. Spin-parities of excited states in (253)Fm fed by the alpha decay of (257)No have been identified on the basis of the measured internal conversion coefficients. The nu3/2(+)[622] configuration has been assigned to the ground state of (257)No as well as to the 124.1 keV level in (253)Fm. It was found that the ground-state configuration of (257)No is different from that of lighter N = 155 isotones.

Evaporation residue cross sections in the 16O+238U reaction were measured for the energy range from above- to extreme sub-barrier. The cross sections are reproduced by a statistical model calculation, for which partial cross sections are calculated by a coupled-channel model taking into account the prolate deformation of 238U. Complete fusion was observed in the collision of the projectile with the tips of the 238U target, in the same way as the side collision.