Y. Gono

A Compton camera for multi-tracer imaging

A high-energy resolution Compton camera consisting of two segmented Ge detectors is proposed for multitracer research. The basic parameters affecting its spatial resolution are described. Monte Carlo simulations were performed to optimize the detector system. Its suitability for multitracer technology was demonstrated by a test experiment.

Gamma-Ray Compton Imaging of Multitracer in Biological Samples Using Strip Germanium Telescope

The feasibility of using a Compton camera for multitracer imaging has been demonstrated with the results of two biological sample imaging experiments. The distribution of the multitracer administered to a soybean sample and a tumor-bearing mouse has been visualized for each nuclide simultaneously. Three-dimensional images of the multitracer have been obtained even though the samples were measured from a fixed direction.

High-spin states and isomers in 136, 137, 138Ce

Abstract High-spin states in 136, 137, 138 Ce have been populated by ( α , x n) reactions and studied using in-beam γ-ray spectroscopic methods. New features result from this investigation. Levels up to I = 15, 33 2 and 16 have been identified in 136, 137, 138 Ce, respectively. In 136, 138 Ce a 10 + isomer has been found which has probably a h 11 2 two-neutron-hole configuration. The level scheme for 137 Ce shows a decoupled band structure different from that of the lighter odd-mass Ce nuclei, where perturbed rotational bands, based on the h 11 2 neutron-hole state were reported. The energies of the 15 2 − → 11 2 − , 19 2 − → 15 2 − and 21 2 + → 19 2 − transitions in 137 Ce are similar to the 2 + → 0 + , 4 + → 2 + and 5 − → 4 + transition energies in 138 Ce, and those of 12 + → 10 + , 14 + → 12 + and 15 → 14 + in 136 Ce. The level structure of these nuclei can be understood if a transition from prolate to oblate shape through a triaxial region occurs between 135 Ce and 137 Ce. Furthermore, in 136 Ce a negative-parity band with even- and odd-spin members was established. In 138 Ce the negative-parity states 7 − and 5 − were observed.

In-beam γ-ray study of 189, 191, 193Au

Abstract High-spin states in 189, 191, 193Au have been populated with (α, xn) reactions and studied by means of in-beam γ-ray spectroscopic methods. Levels are established up to the 43 2 − and 43 2 + states in 193Au. Isomeric states of 5 ns ( 31 2 − ), ≧ 100 ns ( 31 2 + ) in 193Au and of ≧ 100 ns in 191Au were found. A band based on the 35 2 − state which was found in 193Au may be a rotation-aligned band. This 35 2 − state was interpreted to have a [(π h 11 2 ) −1 (ν i 13 2 ) −2 ] 35 2 − configuration. A 10 ns isomer of the h 9 2 proton state was found in 191Au. A band built on this state is established up to the 21 2 − state and discussed within the triaxial-rotor-plus-particle model.

Investigation of high-spin states in odd-odd 190, 192, 194Au nuclei

High-spin states in the odd-odd Au nuclei 190,192,194Au have been populated using (α, xn) reactions and studied by means of in-beam γ-ray and e− spectroscopic methods. In each nucleus two negative-parity rotation-aligned bands were observed, which are based on an 11− isomer and a 12− state, respectively. They may have a configuration resulting from the coupling of a h112 proton-hole and an i132 neutron-hole coupled to a predominantly oblate core in agreement with recent theoretical predictions in the framework of the triaxial-rotor-plus-particle model. Furthermore, side structures based on 15(+) states were established up to spins of I = (20) and (22) in 190,192Au, respectively. The 15(+) and 17(+) members are considered to have a (πh112−1vi132−2(vj) configuration (j = P12, P32 or f52). In the nucleus 194Au a positive-parity rotation-aligned band based on a 7+ state was established up to the 13+ state. This band may have predominantly a (vi132−1πd32−1) configuration.

Excited states in 216Ra

Abstract Excited states in 216Ra have been studied using in-beam spectroscopic techniques. The reactions used were 208Pb(12C, 4n)216Ra and 208Pb(13C, 5n)216Ra at 80 and 95 MeV, respectively. The level scheme of 216Ra was extended up to the (28−) state at 6266 keV. Two new isomers, whose mean lives are 8.7 ± 0.6 ns and 9.7 ± 0.9 ns, were found to be the 19− state at 3763 keV and the (25−) state at 5170 keV. Levels up to the (25 −) state in 216Ra are interpreted as arising from the weak coupling of two neutrons to the excited states in 214Ra.

10+ isomers observed in even-even 78-neutron nuclei

Isomeric states with spinIπ=10+ were found in the nuclei138Nd and140Sm. These states are interpreted as having a [vh11/2]−2 configuration. The systematical behaviour of these isomers in the isotones136Ce,138Nd and140Sm is discussed.

Particle-hole symmetry observed in the angular distributions of γ-rays in 189, 191, 193 Au

Abstract The E2/M1 mixing ratios σ were obtained for the ΔI=1 transitions in 189, 191, 193 Au. The sign of σ for transitions in the h 11 2 and h 9 2 proton bands is positive and negative, respectively. This may be understood in terms of a particle-hole symmetry.

High-spin isomer and level structure of 145Sm

Abstract High-spin states of 145 Sm were studied by using the reactions 20 Ne( 136 Xe,α7n), 16 O( 136 Xe,7n), 139 La( 10 B,4n) and 138 Ba( 13 C,6n). The level scheme was extended up to the state at 14.6 MeV. The excitation energy and the spin-parity of the 0.96 μs high-spin isomer were determined to be 8.8 MeV and ( 49 2 + ), respectively. Experimental results were discussed comparing with the deformed independent particle model calculation. High-spin isomers observed in N = 83 isotones were interpreted to be caused by the sudden shape change from near spherical to oblate. The Z = 64 shell gap energy was found to decrease from 2.4 to 2.0 MeV as the proton number decreases from Z = 64 to 61.

High-spin states in148Tb

High-spin states of148Tb were studied by inbeam γ-ray spectroscopic techniques using141Pr(13C,6n)148Tb and27Al(130Te,9n)148Tb reactions. The level scheme of148Tb was established up to the excitation energy of 11.8MeV. The excitation energy of the high-spin isomer reported previously was revised to be 8.620MeV. The excited states below the isomer could be understood as resulted from the weak couplings of πh11/2 and νf7/2 to those of147Gd and147Tb, respectively.