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The g factor and B(E2) of the first excited 2 + state have been measured following Coulomb excitation of the neutron-rich semimagic nuclide 134 Te (two protons outside 132 Sn) produced as a radioactive beam. The precision achieved matches related g-factor measurements on stable beams and distinguishes between alternative models. The B(E2) measurement exposes quadrupole strength in the 2 + 1 state beyond that predicted by current large-basis shell-model calculations. This additional quadrupole strength can be attributed to coupling between the two valence protons and excitations of the 132 Sn core. However, the wave functions of the low-excitation positive-parity states in 134 Te up to 6 + 1 remain dominated by the π (g 7/2) 2 configuration.

The neutron-capture reaction plays a critical role in the synthesis of the elements in stars and is important for societal applications including nuclear power generation and stockpile-stewardship science. However, it is difficult -if not impossible -to directly measure neutron capture cross sections for the exotic, short-lived nuclei that participate in these processes. In this Letter we demonstrate a new technique which can be used to indirectly determine neutron-capture cross sections for exotic systems. This technique makes use of the (d, p) transfer reaction, which has long been used as a tool to study the structure of nuclei. Recent advances in reaction theory, together with data collected using this reaction, enable the determination of neutron-capture cross sections for short-lived nuclei. A benchmark study of the 95 Mo(d, p) reaction is presented, which illustrates the approach and provides guidance for future applications of the method with short-lived isotopes produced at rare isotope accelerators.Essentially all of the heavy elements are synthesized in astrophysical environments by processes that involve neutron capture. The slow neutron-capture process (the s process) occurs predominantly in the low neutron flux in AGB stars, yielding a nucleosynthesis path that typically deviates only one or two neutrons from β-stability. In contrast, the rapid neutron-capture process (the r process) involves exotic neutron-rich nuclei and requires explosive stellar scenarios with high neutron fluences. The r process is responsible for the creation of roughly half of the elements between iron and bismuth and synthesizes heavy nuclei through the rapid production of neutronrich nuclei via neutron capture and subsequent β decay.The recent observation of the gravitational waves associated with a neutron-star merger [1], and the subsequent kilonova understood to be powered by the decay of lanthanides [2,3], demonstrated that neutron-star mergers are an important r -process site, especially for the heaviest elements. However, r -process abundance patterns are sensitive to astrophysical conditions (cf. [4]). In a "cold" r process (which could occur in a neutron star merger or with the highly accelerated neutrino-driven winds following a core-collapse supernova), equilibrium between neutron capture (n, γ) and photo-dissociation (γ, n) rapidly breaks down, so the rate at which neutron capture proceeds will affect the final r -process abun-dance pattern. The timescales of the cold r process are such that competition between neutron capture and β decay occurs during the bulk of the r -process nucleosynthesis. Neutron-capture rates on unstable nuclei affect the final observed abundance patterns even in the traditional "hot" r process (thought to occur in the neutrinodriven winds in a proto-neutron star resulting from a core-collapse supernova) during the eventual freeze-out, when (n, γ) (γ, n) equilibrium no longer occurs. Accordingly, neutron capture is influential in determining the final r -process abundance pattern, especia...

Single-neutron states in (133)Sn and (209)Pb, which are analogous to single-electron states outside of closed atomic shells in alkali metals, were populated by the ((9)Be, (8)Be) one-neutron transfer reaction in inverse kinematics using particle-γ coincidence spectroscopy. In addition, the s(1/2) single-neutron hole-state candidate in (131)Sn was populated by ((9)Be, (10)Be). Doubly closed-shell (132)Sn (radioactive) and (208)Pb (stable) beams were used at sub-Coulomb barrier energies of 3 MeV per nucleon. Level energies, γ-ray transitions, absolute cross sections, spectroscopic factors, asymptotic normalization coefficients, and excited-state lifetimes are reported and compared with shell-model expectations. The results include a new transition and precise level energy for the 3p(1/2) candidate in (133)Sn, new absolute cross sections for the 1h(9/2) candidate in (133)Sn and 3s(1/2) candidate in (131)Sn, and new lifetimes for excited states in (133)Sn and (209)Pb. This is the first report on excited-state lifetimes of (133)Sn, which allow for a unique test of the nuclear shell model and (132)Sn double-shell closure.

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The β-delayed neutron emission of 83;84 Ga isotopes was studied using the neutron time-of-flight technique. The measured neutron energy spectra showed emission from states at excitation energies high above the neutron separation energy and previously not observed in the β decay of midmass nuclei. The large decay strength deduced from the observed intense neutron emission is a signature of Gamow-Teller transformation. This observation was interpreted as evidence for allowed β decay to 78 Ni core-excited states in 83;84 Ge favored by shell effects. We developed shell model calculations in the proton fpg 9=2 and neutron extended fpg 9=2 þ d 5=2 valence space using realistic interactions that were used to understand measured β-decay lifetimes. We conclude that enhanced, concentrated β-decay strength for neutron-unbound states may be common for very neutron-rich nuclei. This leads to intense β-delayed high-energy neutron and strong multineutron emission probabilities that in turn affect astrophysical nucleosynthesis models. DOI: 10.1103/PhysRevLett.117.092502 β-delayed neutron emission from fission fragments was first observed in 1939 following the neutron bombardment of uranium salts [1]. It was recognized that the delayed neutron energies and emission probabilities, P n , are important parameters to model environments that involve neutron-rich isotopes. Two of the main applications are in nuclear reactor physics [2] and r-process nucleosynthesis [3]. Because β-delayed neutron precursors are neutron rich and far from stability, they are always relatively difficult to produce and study. Advances in detector capabilities allowed for pioneering measurements of neutron emission spectra of fission fragments [4,5]. In these experiments, resonancelike behavior was observed in the neutron emission spectrum [4,6].These efforts were halted in the following decade by several factors. First, it became increasingly difficult to produce species with larger neutron excess. Second, the very influential work by Hardy, Johnson, and Hansen on "pandemonium" attributed the features of the neutron spectra to purely statistical effects and warned against overinterpretation of the measurements [7]. Misinterpretations of their work attributed decay observables of all heavy nuclei to gross features of the decay strength and statistical fluctuations of the level density. A more accurate depiction of their work is that neutron emission characteristics cannot be interpreted without considering the effects of high level density. The pandemonium controversy [8] arose partly from the fact that, at the time, there was no capability to compute nuclear properties using a sufficiently complete microscopic model of the nucleus.State-of-the-art models are now capable of computing decay properties of atomic nuclei, such as lifetimes and branching ratios. It has become increasingly clear that the β-decay observables are profoundly influenced by nuclearPublished by the American Physical Society under the terms of the Creative Commons Attribution 3.0 Lic...