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Title: Level lifetimes in 52 Cr from DSAM following inelastic neutron scattering: Implications for shape coexistence and E 0 strengths
Nuclear shape coexistence is a widespread but not yet well understood phenomenon. Electric monopole (E0) transitions are a particularly sensitive probe of shape coexistence. The firstE0measurements on the Cr isotopes were performed at The Australian National University, but were hampered by missing and imprecise data of the key spectroscopic quantities such as level lifetimes. To address these needs, the low-lying states in52Cr were investigated at the University of Kentucky Accelerator Laboratory with inelastic neutron scattering. γ-ray angular distribution and excitation function measurements were performed to determine level lifetimes, spins and parities, transition mixing ratios, and γ-ray branching ratios. We present new level lifetimes for three states in52Cr along with the implications for E0 transition strengths and shape coexistence in52Cr. more »« less
Mashtakov, K R; Garrett, P E; Olaizola, B; Andreoiu, C; Ball, G C; Bender, P; Bildstein, V; Chester, A; Cross, D S; Dawkins, H; et al
(, EPJ Web of Conferences)
Jentschel, M
(Ed.)
The nuclear structure of the98Zr nucleus was studied through theβ−decay of98Yg.s.at the TRIUMF-ISAC facility. The use of the 8π γ-ray spectrometer with its ancillary detectors SCEPTAR and PACES enabled γ-γ and γ-e−coincidence measurements as well as γ-γ angular correlations. The level spin assignments and transition mixing ratios obtained in this study were in good agreement with previous results. Furthermore, 12 previously unknown states in the low-energy region of98Zr were identified, including the 0+5and 0+6levels at 2418 and 2749 keV, respectively. The 2+and I=1 natures for multiple newly observed and previously known (but not firmly assigned) states have been established. Additionally, the previously assumed pureE2 character of the 2+2→ 2+1367.8-keV transition was confirmed.
Peters, E E; Yates, S W; Brown, B A; Ramirez, A_P D; Mukhopadhyay, S
(, EPJ Web of Conferences)
Jentschel, M
(Ed.)
The low-lying structure of74Ge has been studied with γ-ray detection following inelastic neutron scattering. From excitation function and angular distribution data, the levels and transitions have been characterized including level spins and lifetimes, branching ratios, and multipole mixing ratios. In addition, a number of levels found in the literature for74Ge appear to be erroneously placed. Upon removal of these states from the level scheme, excellent agreement with large-scale shell-model calculations was obtained.
Hou, S Q; Iliadis, C; Pignatari, M; Liu, J B; Trueman, T_C L; Li, J G; Xu, X X
(, Astronomy & Astrophysics)
Context.Accurate42Ti(p,γ)43V reaction rates are crucial for understanding the nucleosynthesis path of the rapid capture process (rpprocess) that occurs in X-ray bursts. Aims.We aim to improve the thermonuclear rates of42Ti(p,γ)43V based on more complete resonance information and a more accurate direct component, together with the recently released nuclear masses data. We also explore the impact of the newly obtained rates on therpprocess. Methods.We reevaluated the reaction rate of42Ti(p,γ)43V by the sum of the isolated resonance contribution instead of the Hauser-Feshbach statistical model. We used a Monte Carlo method to derive the associated uncertainties of new rates. The nucleosynthesis simulations were performed via the NuGrid post-processing code ppn. Results.The new rates differ from previous estimations due to the use of a series of updated resonance parameters and a direct S factor. Compared with the previous results from the Hauser-Feshbach statistical model, which assumes compound nucleus43V with a sufficiently high-level density in the energy region of astrophysical interest, large differences exist over the entire temperature region ofrp-process interest, up to two orders of magnitude. We consistently calculated the photodisintegration rate using our new nuclear masses via the detailed balance principle, and found the discrepancies among the different reverse rates are much larger than those for the forward rate, up to ten orders of magnitude at the temperature of 108K. Using a trajectory with a peak temperature of 1.95×109K, we performed therp-process nucleosynthesis simulations to investigate the impact of the new rates. Our calculations show that the adoption of the new forward and reverse rates result in abundance variations for Sc and Ca of 128% and 49%, respectively, compared to the variations for the statistical model rates. On the other hand, the overall abundance pattern is not significantly affected. The results of using new rates also confirm that therp-process path does not bypass the isotope43V. Conclusions.Our study found that the Hauser-Feshbach statistical model is inappropriate to the reaction rate evaluation for42Ti(p,γ)43V. The adoption of the new rates confirms that the reaction path of42Ti(p,γ)43V(p,γ)44Cr(β+)44V is a key branch of therpprocess in X-ray bursts.
Malik, Vishal; Palit, R; Srivastava, P C; Dey, P; Patel, Deepak; Das, Biswajit; Negi, D; Garg, U; Raut, R; Goel, Nidhi; et al
(, Journal of Physics G: Nuclear and Particle Physics)
Abstract An in-beam gamma-ray spectroscopy study of the even–even nucleus92Mo has been carried out using the30Si +65Cu,18O +80Se reactions at beam energies of 120 and 99 MeV, respectively. Angular distribution from the oriented state ratio (RADO) and linear polarization (Δasym) measurements have fixed most of the tentatively assigned spin-parity of the high-energy levels. A large-scale shell-model calculation using the GWBXG interaction has been carried out to understand the configuration and structure of both positive and negative parity states up to the highest observed spin. The high-spin states primarily originate from the coupling of excited proton- and neutron-core structures in an almost stretched manner. The systematics of the energy required to form a neutron particle-hole pair excitation,νg9/2→νd5/2, is discussed. The lifetimes of a few high-spin states have been measured using the Doppler shift attenuation method. Additionally, a qualitative argument is proposed to explain the comparatively strong E1 transition feeding the 7310.9 keV level.
Hicks, S F; Pecha, R L; Howard, T J; French, A J; Santonil, Z C; Vanhoy, J R; Ramirez, A_P D; Peters, E E; Liu, S H; Prados-Estevez, F M; et al
(, EPJ Web of Conferences)
Jentschel, M
(Ed.)
γ-ray production cross sections have been deduced for reactions with incident neutrons having energies from 1.5 - 4.7 MeV. Similar measurements were made on a natural Ti sample to establish an absolute normalization. The resulting γ-ray production cross sections are compared to TENDL and TALYS calculations, as well as data from previous measurements. The models are found to describe the production cross sections for mostγrays observed from54Mn and54Fe rather well.
Dowie, JTH, Kibédi, T, Peters, EE, and Yates, SW. Level lifetimes in 52 Cr from DSAM following inelastic neutron scattering: Implications for shape coexistence and E 0 strengths. Retrieved from https://par.nsf.gov/biblio/10617731. EPJ Web of Conferences 329. Web. doi:10.1051/epjconf/202532901011.
Dowie, JTH, Kibédi, T, Peters, EE, & Yates, SW. Level lifetimes in 52 Cr from DSAM following inelastic neutron scattering: Implications for shape coexistence and E 0 strengths. EPJ Web of Conferences, 329 (). Retrieved from https://par.nsf.gov/biblio/10617731. https://doi.org/10.1051/epjconf/202532901011
Dowie, JTH, Kibédi, T, Peters, EE, and Yates, SW.
"Level lifetimes in 52 Cr from DSAM following inelastic neutron scattering: Implications for shape coexistence and E 0 strengths". EPJ Web of Conferences 329 (). Country unknown/Code not available: EDP Sciences. https://doi.org/10.1051/epjconf/202532901011.https://par.nsf.gov/biblio/10617731.
@article{osti_10617731,
place = {Country unknown/Code not available},
title = {Level lifetimes in 52 Cr from DSAM following inelastic neutron scattering: Implications for shape coexistence and E 0 strengths},
url = {https://par.nsf.gov/biblio/10617731},
DOI = {10.1051/epjconf/202532901011},
abstractNote = {Nuclear shape coexistence is a widespread but not yet well understood phenomenon. Electric monopole (E0) transitions are a particularly sensitive probe of shape coexistence. The firstE0measurements on the Cr isotopes were performed at The Australian National University, but were hampered by missing and imprecise data of the key spectroscopic quantities such as level lifetimes. To address these needs, the low-lying states in52Cr were investigated at the University of Kentucky Accelerator Laboratory with inelastic neutron scattering. γ-ray angular distribution and excitation function measurements were performed to determine level lifetimes, spins and parities, transition mixing ratios, and γ-ray branching ratios. We present new level lifetimes for three states in52Cr along with the implications for E0 transition strengths and shape coexistence in52Cr.},
journal = {EPJ Web of Conferences},
volume = {329},
publisher = {EDP Sciences},
author = {Dowie, JTH and Kibédi, T and Peters, EE and Yates, SW},
editor = {Jentschel, M}
}
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