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(Color online) Time distribution of βp events correlated with several implanted nuclides. Fits take into account the exponential βp decay of parent ground (green) and isomeric states (blue) and a constant background (red). In the case of 96 Cd, the contribution of the β-decay daughter 96 Ag (blue) and the 97 Cd contamination (red) had to be included. The sum of all components is also shown (black).
Source publication
Beta-delayed proton emission from nuclides in the neighborhood of 100Sn was
studied at the National Superconducting Cyclotron Laboratory. The nuclei were
produced by fragmentation of a 120 MeV/nucleon 112Sn primary beam on a Be
target. Beam purification was provided by the A1900 Fragment Separator and the
Radio Frequency Fragment Separator. The fra...
Contexts in source publication
Context 1
... Fig. 4 and Fig. 5 are presented the energy spectra and βp-decay curves, respectively, for several implanted nuclei. The deduced half-lives and b βp values are summarized in Table I. The decay properties of these nuclides are discussed in detail in the following ...
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... in the DSSD and six βp events were identified. A b βp value of 3 +1.9 −1.7 % was deduced, given that one of the βp events might be attributed to background, based on the measured background rate. The uncertainty was determined by assuming a binomial probability distribution and applying a 95% confidence level. A fit to the βp-decay curve in Fig. 5 ...
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... the decay of the shorter-lived, presumed 8 + state by gating the decay curve of 96 Ag by the 325-keV γ -ray transition in 96 Pd. A half-life of 6.8(10) s was deduced for the longer- lived, proposed 2 + state via a two-component fit of the βp activity, where the short-lived component of the decay curve was fixed to a half-life value of 4.39 s [ Fig. 5(d)]. The same fit provided the relative contributions of the two 96 Ag states to the βp activity. The relative contributions of the two β-decaying states to the overall β activity were obtained by comparing the intensities of the 325-and 1415-keV γ rays. The 325-keV γ ray is mainly fed by the β decay of the presumed 8 + state, while the ...
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... βp-energy spectrum [ Fig. 4(d)] and the βp-decay half-life of 1.80(8) s obtained in the present work [ Fig. 5(e)] agree with the results reported in Ref. [2], resolving the discrepancy with the earlier βp-decay data Ref. [28] and supporting the conclusions of Ref. [2]. A b βp value of 2.5(3)% was also measured. No evidence was found here for βp decay of the 21/2 + isomeric state in 95 Pd, which might be populated following the β decay of 95 Ag. ...
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... for the decay of 97 Cd were previously published [18], and a summary is provided here for completeness. Evidence for a high-spin isomer was found, based on the different half-lives of 97 Cd βp-decay events coincident with γ rays from the deexcitation of states in 96 Pd. In addition, two components were evident in the 97 Cd decay curve as shown in Fig. 5(f). Half-life values of 1.10(8) and 3.8(2) s and b βp values of 12(2)% and 25(4)% were deduced for ground and isomeric states, respectively. Details can be found in Ref. [18] and Table. ...
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... the half-life of 96 Ag. A half-life value of 7.5(15) s was obtained for 96 Ag, indicating that the dominant β-decay branching of 96 Cd feeds the 2 + state in 96 Ag. The decay curve fitting was then repeated with the b βp and half-life values of 96 Ag fixed to the known values for the 2 + state. The resulting fit of the decay curve is shown in Fig. ...
Citations
... The models have difficulties describing both the isomer excitation energies and ground-state electromagnetic moments along the indium chain. Considerable experimental and theoretical efforts have concentrated on the region around 100 Sn [1], the heaviest known self-conjugate and doubly magic nucleus (N ¼ Z ¼ 50), including decay spectroscopy [2][3][4][5][6][7][8][9], laser spectroscopy [10][11][12], Coulomb excitation studies [13][14][15], and mass measurements [16][17][18][19]. The similar valence orbitals that the protons and neutrons occupy are expected to enhance the effect of proton-neutron pairing, while the proximity of the double shell closure and proton drip line make it a unique laboratory to test our understanding of the strong interaction. ...
The excitation energy of the 1/2− isomer in 99In at N=50 is measured to be 671(37) keV and the mass uncertainty of the 9/2+ ground state is significantly reduced using the ISOLTRAP mass spectrometer at ISOLDE/CERN. The measurements exploit a major improvement in the resolution of the multireflection time-of-flight mass spectrometer. The results reveal an intriguing constancy of the 1/2− isomer excitation energies in neutron-deficient indium that persists down to the N=50 shell closure, even when all neutrons are removed from the valence shell. This trend is used to test large-scale shell model, ab initio, and density functional theory calculations. The models have difficulties describing both the isomer excitation energies and ground-state electromagnetic moments along the indium chain.
... [395][396][397]). Recent decay studies have focused on β-delayed particle emission probabilities (e.g., [379,[398][399][400][401][402]). Modifications of β-decay rates in the astrophysical environment, for example due to continuum electron capture, have been calculated and are significant in some cases [403]. ...
Nuclear astrophysics is a field at the intersection of nuclear physics and astrophysics, which seeks to understand the nuclear engines of astronomical objects and the origin of the chemical elements. This white paper summarizes progress and status of the field, the new open questions that have emerged, and the tremendous scientific opportunities that have opened up with major advances in capabilities across an ever growing number of disciplines and subfields that need to be integrated. We take a holistic view of the field discussing the unique challenges and opportunities in nuclear astrophysics in regards to science, diversity, education, and the interdisciplinarity and breadth of the field. Clearly nuclear astrophysics is a dynamic field with a bright future that is entering a new era of discovery opportunities.
... Efforts continue at NSCL (National Superconducting Cyclotron Laboratory, Michigan, USA) to contribute to the region [58], e.g., with spectroscopy using knock-out reactions [59], or the recent mass measurement of 80 Zr [60]. At GSI, revisited isomeric decay in 102 Sn and resulting effective neutron and proton charges based on state-of-the-art shellmodel calculations were published [61], 13 years after the RISING [62] experiment. ...
... Efforts continue at NSCL (National Superconducting Cyclotron Laboratory, Michigan, USA) to contribute to the region [58], e.g., with spectroscopy using knock-out reactions [59], or the recent mass measurement of 80 Zr [60]. At GSI, revisited isomeric decay in 102 Sn and resulting effective neutron and proton charges based on state-of-the-art shell-model calculations were published [61], 13 years after the RISING [62] experiment. ...
Inevitable progress has been achieved in recent years regarding the available data on the structure of 100Sn and neighboring nuclei. Updated nuclear structure data in the region is presented using selected examples. State-of-the-art experimental techniques involving stable and radioactive beam facilities have enabled access to those exotic nuclei. The analysis of experimental data has established the shell structure and its evolution towards N = Z = 50 of the number of neutrons, N, and the atomic number, Z, seniority conservation and proton–neutron interaction in the g9/2 orbit, the super-allowed Gamow–Teller decay of 100Sn, masses and half-lives along the rapid neutron-capture process (r-process) path and super-allowed α decay beyond 100Sn. The status of theoretical approaches in shell model and mean-field investigations are discussed and their predictive power assessed. The calculated systematics of high-spin states for N = 50 isotopes including the 5− state and N = Z nuclei in the g9/2 orbit is presented for the first time.
... Ten single-sided segmented strip detectors (SSSSDs) were placed farther downstream for Q β measurements. Events accompanying proton emission were separated from positron events by requiring a minimum of 1500 keV energy deposited in a single pixel of a DSSSD as described in Ref. [31]. ...
We report on new or more precise half-lives, β-decay endpoint energies, and β-delayed proton emission branching ratios of Pd91, Cd95, In97, and Sn99. The measured values are consistent with known mirror transitions in lighter Tz=−1/2 nuclei, shell-model calculations, and various mass models. In addition to the β-decaying (9/2+) ground state, circumstantial evidence for a short-lived, proton-emitting isomer with spin (1/2−) was found in In97. Based on the experimental data, a semiempirical theory on proton emission, and shell-model calculations, the proton separation energy of the In97 ground state was determined to be −0.10±0.19 MeV. The existence of the short-lived, proton-unstable (1/2−) isomer in In97 establishes Cd96 as an rp-process waiting point.
... Many of the topics listed above are manifest in numerous isomeric states of N,Z 50 nuclei [7], which offer important insights into their structure: E2 seniority isomers in N = 50 isotones 92 Mo, 94 Ru, 96 Pd, and 98 Cd [8][9][10][11]; a high-spin, negative-parity isomer in 94 Pd [48] with = 1,3 electric transitions (E1, E3); multiple isomers in 95 Ag [12] decaying via = 3,4 electric transitions (E3, E4); N = Z spin-gap isomers in 94 Ag, 96 Cd, and 98 In [3,[13][14][15][16][17][18][19]; and core-excited isomers in 96 Ag and 98 Cd [20][21][22]. This is by no means an exhaustive list. ...
... The majority of the ions were implanted in the middle module of the three 1-mm-thick double-sided silicon strip detectors (DSSSDs) of WAS3ABi, where each DSSSD was segmented into 60 × 40 1-mm-wide strips in the x and y directions, respectively. Particle decay events were correlated to ion implantation events as described in Ref. [19], which used a similar set of segmented Si detectors. γ rays following decay events were detected with the Euroball-RIKEN Cluster Array (EURICA) [44], featuring a total of 84 HPGe crystals that surrounded WAS3ABi in a 4π geometry. ...
DOI:https://doi.org/10.1103/PhysRevC.96.049901
... Many of the topics listed above are manifest in numerous isomeric states of N,Z 50 nuclei [7], which offer important insights into their structure: E2 seniority isomers in N = 50 isotones 92 Mo, 94 Ru, 96 Pd, and 98 Cd [8][9][10][11]; a high-spin, negative-parity isomer in 94 Pd [48] with = 1,3 electric transitions (E1, E3); multiple isomers in 95 Ag [12] decaying via = 3,4 electric transitions (E3, E4); N = Z spin-gap isomers in 94 Ag, 96 Cd, and 98 In [3,[13][14][15][16][17][18][19]; and core-excited isomers in 96 Ag and 98 Cd [20][21][22]. This is by no means an exhaustive list. ...
... The majority of the ions were implanted in the middle module of the three 1-mm-thick double-sided silicon strip detectors (DSSSDs) of WAS3ABi, where each DSSSD was segmented into 60 × 40 1-mm-wide strips in the x and y directions, respectively. Particle decay events were correlated to ion implantation events as described in Ref. [19], which used a similar set of segmented Si detectors. γ rays following decay events were detected with the Euroball-RIKEN Cluster Array (EURICA) [44], featuring a total of 84 HPGe crystals that surrounded WAS3ABi in a 4π geometry. ...
Half-lives and energies of γ rays emitted in the decay of isomeric states of nuclei in the vicinity of the doubly magic Sn100 were measured in a decay spectroscopy experiment at Rikagaku Kenkyusho (The Institute of Physical and Chemical Research) of Japan Nishina Center. The measured half-lives, some with improved precision, are consistent with literature values. Three new results include a 55-keV E2γ ray from a new (4+) isomer with T1/2=0.23(6)μs in Rh92, a 44-keV E2γ ray from the (15+) isomer in Ag96, and T1/2(6+)=13(2) ns in Cd98. Shell-model calculations of electromagnetic transition strengths in the (p1/2,g9/2) model space agree with the experimental results. In addition, experimental isomeric ratios were compared to the theoretical predictions derived with an abrasion-ablation model and the sharp cutoff model. The results agreed within a factor of 2 for most isomers. From the nonobservation of time-delayed γ rays in Sn100, new constraints on the T1/2, γ-ray energy, and internal conversion coefficients are proposed for the hypothetical isomer in Sn100.
... In [15], the γ-transition with energy 172 keV, observed in the α-decay measurements of the chain 109 Xe 105 Te 101 Sn, was assigned to the deexcitation of the first excited + 5 2 state to the + 7 2 ground state, while the opposite order was proposed in a previous experiment [16], where a γ-ray transition of similar energy was identified in an in-beam γ-ray experiment by tagging on β-delayed protons from 101 Sn. An attempt to establish the spin of the first excited state in 101 Sn was also performed in a β-delayed proton emission experiment [17], but unfortunately it was not possible to draw a definite conclusion, more precise mass measurements being required. Our prediction for 101 Sn is in line with [15], where the experimental finding was substantiated by SM calculations very similar to those presented in this paper. ...
This paper presents a short overview of a procedure we have recently introduced, dubbed the double-step truncation method, which is aimed to reduce the computational complexity of large-scale shell-model calculations. Within this procedure, one starts with a realistic shell-model Hamiltonian defined in a large model space, and then, by analyzing the effective single particle energies of this Hamiltonian as a function of the number of valence protons and/or neutrons, reduced model spaces are identified containing only the single-particle orbitals relevant to the description of the spectroscopic properties of a certain class of nuclei. As a final step, new effective shell-model Hamiltonians defined within the reduced model spaces are derived by way of a unitary transformation of the original large-scale Hamiltonian. A detailed account of this transformation is given and the merit of the double-step truncation method is illustrated by discussing few selected results for ⁹⁶Mo, described as four protons and four neutrons outside ⁸⁸Sr. Some new preliminary results for light odd-tin isotopes from A =101 to 107 are also reported.
... For a possible 2p capture process bypassing the 68 Se roadblock, the proton separation energy of proton-unbound 69 Br is critical and two complementary measurements of S Br p 69 ( ) have been performed [220,221] whose results restrict the reaction flow via the 68 Se(2p,γ) bypass to at most 20% [221]. Beta-decay halflives and βdelayed proton decay branchings in the 100 Sn region were measured and constrained the composition of the type I x-ray burst ashes [224][225][226]. The pioneering halflife measurement of 96 Cd, for example, excluded to possibility that x-ray bursts are the major source of 96 Ru in the solar system [226]. ...
The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is a scientific user facility that offers beams of rare isotopes at a wide range of energies. This article describes the facility, its capabilities, and some of the experimental devices used to conduct research with rare isotopes. The versatile nuclear science program carried out by researchers at NSCL continues to address the broad challenges of the field, employing sensitive experimental techniques that have been developed and optimized for measurements with rare isotopes produced by in-flight separation. Selected examples showcase the broad program, capabilities, and the relevance for forefront science questions in nuclear physics, addressing, for example, the limits of nuclear existence; the nature of the nuclear force; the origin of the elements in the cosmos; the processes that fuel explosive scenarios in the Universe; and tests for physics beyond the standard model of particle physics. NSCL will cease operations in approximately 2021. The future program will be carried out at the Facility for Rare Isotope Beams, FRIB, presently under construction on the MSU campus adjacent to NSCL. FRIB will provide fast, stopped, and reaccelerated beams of rare isotopes at intensities exceeding NSCL's capabilities by three orders of magnitude. An outlook will be provided on the enormous opportunities that will arise upon completion of FRIB in the early 2020s.
The isomeric structure and properties in proton-rich nuclides are crucial for determining the path of the rapid proton capture process (rp-process). For example, bound nuclei inside the dripline can have unbound isomeric states and change the rp-process pathway. The configuration interaction shell model is used to investigate nuclei around the Z=N line at the southwest region of Sn100. The excitation mechanism of 1/21− isomers is identified as dominated by exciting one nucleon in the 1p1/2 orbit to the 0g9/2 orbit. The study explores the decay properties of both the ground and isomeric states. Remarkably, competitive β+ decay and proton emission are predicted in the unbound 1/21− isomer of Sn97, suggesting potential influences on the rp-process pathway.
The excitation energy of the 1/2$^-$ isomer in $^{99}$In at ${N=50}$ is measured to be 671(37) keV and the mass uncertainty of the 9/2$^+$ ground state is significantly reduced using the ISOLTRAP mass spectrometer at ISOLDE/CERN. The measurements exploit a major improvement in the resolution of the multi-reflection time-of-flight mass spectrometer. The results reveal an intriguing constancy of the $1/2^-$ isomer excitation energies in neutron-deficient indium that persists down to the $N = 50$ shell closure, even when all neutrons are removed from the valence shell. This trend is used to test large-scale shell model, \textit{ab initio}, and density functional theory calculations. The models have difficulties describing both the isomer excitation energies and ground-state electromagnetic moments along the indium chain.
