First observation of a shape isomer and a low-lying strongly-coupled prolate band in neutron-deficient semi-magic 187Pb

Prompt and delayed γ-ray spectroscopy of the neutron-deficient, semi-magic isotope 187Pb has been performed using the recoil-decay and isomer-decay tagging techniques at the Argonne Gas-Filled Analyzer. A new 5.15(15)-μs isomeric state at only 308 keV above the spherical 3/2− ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2−[514] Nilsson state in the isotone 185Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in 187Pb is proposed to originate from the same configuration. The retarded character of the 308-keV (7/2−)→3/2gs− transition with a deduced B(E2)=5.6(2)×10−4 W.u. can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The excitation energy of the isomer is surprisingly low, being roughly half of the excitation energies of the known 0+ intruder bandheads in the neighboring 186,188Pb isotopes. The combined results of the present work and the previous α-decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of 187Pb, which is well reproduced by the potential-energy surface calculations

Establishment of an in vitro plant regeneration protocol for Casuarina cunninghamiana Miq. via indirect organogenesis

An in vitro plant regeneration protocol via indirect organogenesis from morphogenetic callus was established for Casuarina cunninghamiana Miq. Effects of plant growth regulator NAA (naphthaleneacetic acid) and BAP (6-benzylaminopurine), sucrose and AgNO3 on callus induction, adventitious bud differentiation and shoot development were examined. Explants used were epicotyl fragments from 45-day-old seedlings. The largest callus (4.29 mm in diameter) was obtained after 1 month on a basic culture medium consisting of Murashige and Skoog A1/2 macro- and full strength micro- elements, Nitsch and Nitsch vitamins, supplemented with 0.54 mu M NAA, 3.30 mu M BAP, and 30 g L-1 sucrose. The calli were subcultured in the same medium above for 2 months. They were then cultured for another 2 months for adventitious bud differentiation and shoot development. The highest mean adventitious bud differentiation, number of shoots formed per callus and number of shoots a parts per thousand yen2 cm long per callus (47.50%, 27.38 and 4.75, respectively) were achieved on the above medium modified with NAA at 0.27 mu M and supplemented with AgNO3 1 mg L-1. Shoots were successfully rooted without plant growth regulator and the rooted plantlets survived and grew normally. This protocol for in vitro plant regeneration provides a tool not only for vegetative propagation but also for plant genetic transformation and gene function studies of C. cunninghamiana

Characterization of TiAl alloy films for potential application in MEMS bimorph actuators

10.1016/S1369-8001(02)00055-0Materials Science in Semiconductor Processing5135-3

Configurations of the low-lying states in 146Eu^{146}\mathrm{Eu}

International audienceThe low-lying states of Eu146 populated in the decay of the 9+ isomer were studied. The γ-ray intensities were reanalyzed employing germanium detectors, and the lifetimes of the 61− and 62− states were measured using the mirror symmetric centroid difference (MSCD) method with fast-timing LaBr3(Ce) scintillator detectors. The B(M1) values of the 61−→51− and 62−→51− transitions were deduced, and all observed states were interpreted as members of the πd5/2−1νf7/2 and πg7/2−1νf7/2 multiplets. In particular, the 51− level is shown to be dominated by the πd5/2−1νf7/2 configuration, solving the discrepancy in its configuration assignment proposed in previous works. These experimental results were compared with the shell model calculations using several different effective interactions. The systematics of low-lying structure in the N=83 isotones Pr142, Pm144, and Eu146 was established

Probing 93mMo^{93m}\mathrm{Mo} Isomer Depletion with an Isomer Beam

International audienceThe isomer depletion of Mo93m was recently reported [Chiara et al., Nature (London) 554, 216 (2018)] as the first direct observation of nuclear excitation by electron capture (NEEC). However, the measured excitation probability of 1.0(3)% is far beyond the theoretical expectation. In order to understand the inconsistency between theory and experiment, we produce the Mo93m nuclei using the C12(Kr86,5n) reaction at a beam energy of 559 MeV and transport the reaction residues to a detection station far away from the target area employing a secondary beam line. The isomer depletion is expected to occur during the slowdown process of the ions in the stopping material. In such a low γ-ray background environment, the signature of isomer depletion is not observed, and an upper limit of 2×10-5 is estimated for the excitation probability. This is consistent with the theoretical expectation. Our findings shed doubt on the previously reported NEEC phenomenon and highlight the necessity and feasibility of further experimental investigations for reexamining the isomer depletion under low γ-ray background

First observation of the decay of the 13/2+ isomer in 183Hg and B(M2) systematics of neutron transitions across the nuclear chart

The decay of the 13/2+ isomeric state in 183Hg was observed for the first time following the α decay of the 13/2+ isomer in 187Pb produced in the 142Nd(50Cr, 2p3n) reaction. Using α−γ delayed coincidence measurements, the half-life of this isomer was measured to be 290(30) μs. This isomer is proposed to deexcite by an unobserved low-energy M2 transition to the known 9/2− member of a strongly prolate-deformed 7/2−[514] band, followed by a 105-keV M1 transition to the bandhead. A lower limit of B(M2) ≥ 0.018 W.u. was deduced for the unobserved transition. The presumed retardation is proposed to be due to the notable shape change between the initial, nearly spherical, and the final, strongly deformed, states. A similar scenario is also considered for the 13/2+ isomer in 181Hg, suggesting both are cases of shape isomers. The B(M2) systematics of neutron transitions across the nuclear chart is discussed