Search NASA⌕ Search

SEARCH · Search NASA

Results for “Isomeric states”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

β -delayed neutron spectroscopy of Co 70 , 72 ground-state and isomeric-state decays

Here, the β-decaying states of 70,72 Co were studied at the National Superconducting Cyclotron Laboratory using the VANDLE neutron time-of-flight array. The (6 - ,7 - )⁢β-decaying state in 70 Co is near-spherical with a lifetime of 113 ± 7 ms, and the low-spin (1 + ,2 + )⁢β-decaying state is postulated to be the prolate deformed ground state with a lifetime of 508 ± 7 ms. Both decay predominantly to the bound states of 70 Ni. For the first time neutron-emissions from neutron unbound states from both the (6 - ,7 - ) and (1 + ,2 + )⁢β decays were measured. Even with the low statistics data, we were able to disentangle the neutron emission from both decays, which enabled a determination of β-decay strength above the neutron separation energy of 70 Ni. Neutron emission probabilities were measured to be 7.1 ± 1.5% and 9.4 ± 1.7%, respectively, for the (6 - ,7 - ) and (1 + ,2 + ) decays. The decay pattern of the 70 Co is driven by neutron f 5/2 to proton f 7/2 Gamow-Teller transformation. The observed population of neutron unbound states is attributed to the conversion of p 1/2 and p 3/2 neutrons to p 3/2 and p 1/2 protons excited across the Z = 28 closed shell.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Decay of a microsecond seniority 3 isomeric state in Hf 155

Excited states in the neutron-deficient nuclide Hf 155 have been investigated in experiments performed at the Accelerator Laboratory of the University of Jyväskylä. The Hf 155 nuclei were produced in fusion-evaporation reactions induced by beams of 295 and 315 MeV Ni 58 ions bombarding an isotopically enriched Pd 102 target and separated using the recoil mass separator MARA. An isomeric state having a half-life of 510(30) ns was discovered and is interpreted as a seniority υ = 3 , ( π h 11 / 2 2 ⊗ ν f 7 / 2 ) 27 / 2 − configuration. The γ -ray transitions emitted in the deexcitation of the isomeric state to the ground state were identified and a level scheme was constructed, from which the excitation energy of the isomer was determined to be 2581.5(10) keV. A B ( E 2 ) value of 0.45(3) W.u. was deduced for the 105.4 keV transition depopulating the isomeric state. The deduced level scheme and B ( E 2 ) value are compared with systematics and shell-model calculations. Published by the American Physical Society 2024

Physics↗
DOE OSTI2025

Decay spectroscopy of an isomeric state in Md251

Excited states in Md251 have been populated by decay of an isomeric state at Ex≈1174 keV and studied via delayed γ-ray spectroscopy. We observe the population of two rotational bands, one of which we identify as the Nilsson π72[514] ground-state band and the other we propose is based on the π92[624] configuration. From the observed decay pattern, we suggest that the isomer spin parity is 232+, with the three-quasiparticle configuration π72[514]⊗{ν72[624]⊗ν92[734]}Kπ=8−. We compare our results to theoretical predictions of the single- and multi-quasiparticle structure of Md251.

Morse, C↗
DOE OSTI2026

Isomeric states in the neutron-rich 𝑁 = 108 nuclei 178 Yb and 179 Lu

A multinucleon transfer reaction with a 136 Xe beam and a gold-backed 176 Yb target populated isomers in N = 108 178 Yb and 179 Lu. The single decay from the t 1/2 = 203(16) ns isomer in 178 Yb to the I π = 4 + level in the ground-state band suggests a I π = 4 − assignment, and multiquasiparticle calculations associate this state with the K π = 4 − , ν 2 (1/2[510], 9/2[624]) configuration. At least two isomers were observed in 179 Lu. One likely couples the K π = 4 − configuration found in 178 Yb to the 9/2[514] quasiproton orbital to form a K π = 17/2 + level (t 1/2 = 1.0(4) µs) which primarily decays into the rotational band based on the 9/2[514] state. A second isomer was observed to decay into this same band, but at higher energy and spin. Based on its feeding pattern, its similarity to an isomer found in 181 Ta, and a multiquasiparticle calculation, it is proposed to correspond to a K π = 29/2 − state based on the π9/2[514]ν 2 (9/2[624], 11/2[615]) configuration. As a result, an analysis of the reduced hindrance factors for negative-parity, two-quasineutron isomers in the rare-earth region is presented as well.

150 ≤ A ≤ 189↗
DOE OSTI2025

Decay spectroscopy of an isomeric state in 251 Md

Superheavy elements ( Z ≥ 104) owe their existence to quantum shell effects which stabilize them against fission. Experimental studies of their structure are challenging, and only recently has direct information begun to emerge. Meanwhile, the comparative ease of producing the transfermium nuclei offers an alternative approach. These nuclei are well-deformed ( β 2 ≈ 0.28) owing to the existence of deformed gaps in the single particle spectrum near Z = 100 and N = 152. Because of this, the proton orbitals near the Fermi surface in this region are expected to originate from the spherical sub shells which define the shell gaps near Z = 114. In this sense, the transfermium nuclei act as a testing ground for theoretical models used to describe the superheavy region. Deformed odd-mass nuclei are of particular interest since they can provide direct insight into the single particle structure.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2019

Solid-State Isomerization and Infrared Band Strengths of Two Conformational Isomers of Cyclopropanecarboxaldehyde, A Candidate Interstellar Molecule

At least a dozen of the known interstellar molecules possess a formyl group (HCO), suggesting that other such species exist and await discovery in the interstellar medium. Here, we examine the mid-infrared (mid-IR) spectrum and selected physical properties of one such candidate, cyclopropanecarboxaldehyde, in amorphous ices. Mid-IR transmission spectra of solid cyclopropanecarboxaldehyde are presented for the first time and used to determine the cis-to-trans ratio of conformational isomers present in amorphous samples. The measured ratio is compared to one from an electron-diffraction study of the gas-phase compound. The cis-to-trans isomerization in the amorphous compound is followed, and the activation energy is determined. The first IR band strengths for solid cyclopropanecarboxaldehyde are reported. Also presented are refractive indices and densities at 15 K for amorphous forms of two related compounds, cyclopropane and cyclopropanemethanol. Two low-temperature reactions for the interstellar formation of cyclopropanecarboxaldehyde are briefly described.

band strengths↗
DOE OSTI2023

Nuclear Wallet Cards

The Nuclear Wallet Cards present properties for ground and isomeric states of all known nuclides. It provides the following: Spin and parity assignments, Nuclear mass excesses, Half-lives, isotopic abundances, Decay modes. Appendices contain properties of elements, fundamental constants and other useful information.

Decay modes↗
DOE OSTI2024

Cross-shell excited configurations in the structure of 34 Si

The cross-shell excited states of 34 Si have been investigated via β decays of the 4 − ground state and the 1 + isomeric state of 34 Al. Since the valence protons and valence neutrons occupy different major shells in the ground state as well as the intruder 1 + isomeric state of 34 Al, intruder levels of 34 Si are populated via allowed β decays. Spin assignments to such intruder levels of 34 Si were established through γ-γ angular correlation analysis for the negative-parity states. The configurations of such intruder states play crucial roles in our understanding of the N = 20 shell gap evolution. A configuration interaction model derived from the FSU Hamiltonian was utilized in order to interpret the intruder states in 34 Si. Furthermore, shell model interaction derived from a more fundamental theory with the valence space in medium similarity renormalization group method was also employed to interpret the structure of 34 Si.

20 ≤ A ≤ 38↗
NASA NTRS1994

Conformational Characteristics of Poly(tetrafluoroethylene) (PTFE) Based Upon Ab Initio Electronic Structure Calculations on Model Molecules

Conformational energy contours of perfluoroalkanes, determined from ab initio calculations, confirm the well-known spitting of trans states into two minima at plus or minus 17 degrees but also show that the gauche states split as well, with minima at plus or minus 124 degrees and plus or minus 84 in order to relieve steric crowding. The directions of such split distortions from the perfectly staggered states are strongly coupled for adjacent pairs of bonds in a manner identical to the intradyad pair for poly (isobutylene) chains. These conformational characteristics are fully represented by a six-state rotational isomeric state (RIS) model for PTFE comprised of t(+), t(-), g(sup +)+, g(sup +)-, g(sup -) + and g(sup -)-states, located at the split energy minima. The resultant 6 x 6 statistical weight matrix is described by first-order interaction parameters for the g+(+) (ca. 0.6 kcal/mol) and g+- (ca. 2.0 kcal/mol) states, and second order parameters for the g(sup +)+g(sup +)+ (ca 0.6 kcal/mol) and g(sup +)+g(sup -)+ (ca. 1.0 kcal/mol) states. This six-state RIS model, without adjustment of the geometric or energy parameters as determined from the ab initio calculations, predicts the unperturbed chain dimensions and the fraction of gauche bonds as a function of temperature for PTFE in good agreement with available experimental values.

Smith, Grant D.↗
DOE OSTI2023

Resonant X-ray excitation of the nuclear clock isomer 45 Sc

Resonant oscillators with stable frequencies and large quality factors help us to keep track of time with high precision. Examples range from quartz crystal oscillators in wristwatches to atomic oscillators in atomic clocks, which are, at present, our most precise time measurement devices. The search for more stable and convenient reference oscillators is continuing. Nuclear oscillators are better than atomic oscillators because of their naturally higher quality factors and higher resilience against external perturbations. One of the most promising cases is an ultra-narrow nuclear resonance transition in 45 Sc between the ground state and the 12.4-keV isomeric state with a long lifetime of 0.47 s (ref. 10 ). The scientific potential of 45 Sc was realized long ago, but applications require 45 Sc resonant excitation, which in turn requires accelerator-driven, high-brightness X-ray sources that have become available only recently. Here we report on resonant X-ray excitation of the 45 Sc isomeric state by irradiation of Sc-metal foil with 12.4-keV photon pulses from a state-of-the-art X-ray free-electron laser and subsequent detection of nuclear decay products. Simultaneously, the transition energy was determined as ${\mathrm{12,389.59}}_{+0.12\left({\rm{syst}}\right)}^{\pm 0.15\left({\rm{stat}}\right)}\,{\rm{eV}}$ with an uncertainty that is two orders of magnitude smaller than the previously known values. These advancements enable the application of this isomer in extreme metrology, nuclear clock technology, ultra-high-precision spectroscopy and similar applications.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Precise mass measurement of the longest odd-odd chain of nuclei with 1+ ground states

Precise mass measurements of the ground and isomeric states of the odd-odd Rh108,110,112,114,116 were performed using the Canadian Penning Trap at Argonne National Laboratory, showing good agreement with recent JYFLTRAP measurements. A new possible isomeric state of Rh114 was also observed. These isotopes are part of the longest odd-odd chain of identical ground-state spin-parity assignment of 1+, spanning Rh104–118, despite being in a region of deformation. Realistic phenomenological mean-field calculations using the “universal” Wood-Saxon Hamiltonian were performed, which explained this phenomenon for the first time. In addition, multiquasiparticle blocking calculations were performed to study the configuration of low-lying states in the odd-odd Rh nuclei, elucidating anomalous isomeric yield ratio observed for Rh114.

Liu, B↗
DOE OSTI2026

Total absorption spectroscopy of two isomers in 70 Cu influencing nucleosynthesis signatures

Isomers have long been known to be important for astrophysical nucleosynthesis processes, yet they are often neglected in network calculations due to computational limitations or lack of data. "Astromers" are astrophysically metastable nuclear states that can greatly impact nucleosynthesis pathways. In this work we show that astromers further impact the time-dependent electromagnetic signal during heavy element nucleosynthesis. In an experiment performed at the National Superconducting Cyclotron Laboratory, three 𝛽-decaying states of 70 Cu (6 − ground state, and two isomeric states: 3 − and 1 + ) were produced. 𝛽-feeding values were extracted from experimental spectra and compared to shell-model and QRPA+PVC calculations. Here, average 𝛾-ray energies from the 𝛽-decay events were incorporated into simulations of heavy element nucleosynthesis and were found to exhibit different energy release profiles over time, which may impact, in aggregate, time-dependent observable signals.

59 ≤ A ≤ 89↗
DOE OSTI2024

Improving Fission Products at CARIBU: Near Field Detection (Q1/FY24 Quarterly Progress Report)

The article on “Direct Mass Measurements to Inform the Behavior for 128mSb in Nucleosynthesis Environments” by Daniel Hoff et al., recently published in Physical Review Letters. The results of the work are a combination of an extraordinary work on precision mass measurements performed with the Canadian Penning Trap at ANL (the most precise mass measurement of the ground state and the isomeric state in 128Sb performed to date), and an extensive nucleosynthesis theory calculation that include isomers performed by the theorists at LANL.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Decay spectroscopy at the two-proton drip line: Radioactivity of the new nuclides 160 Os and 156 W

The radioactivity of $^{160}_{76}$Os 84 and $^{156}_{74}$W 82 that lie at the two-proton drip line has been measured in an experiment performed at the Accelerator Laboratory of the University of Jyväskylä. The 160 Os nuclei were produced using fusion-evaporation reactions induced by a beam of 310 MeV 58 Ni ions bombarding a 106 Cd target. The 160 Os ions were separated in flight using the recoil separator MARA and implanted into a double-sided silicon strip detector, which was used to measure their decays. The α decays of the ground state of 160 Os (Ε α = 7092(15) keV, t 1/2 = 97$^{+97}_{-32}$ μs) and its isomeric state (Ε α = 8890(10) keV, t 1/2 = 41$^{+15}_{-9}$ μs) were measured, allowing the excitation energy of the isomer to be determined as 1844(18) keV. These α-decay properties and the excitation energy of the isomer are compared with systematics. The α decays were correlated with subsequent decays to investigate the β decays of the ground state of 156 W, revealing that unlike its isotones, both low-lying isomers were populated in its daughter nuclide, 156 Ta. An improved value for the half-life of the proton-decaying high-spin isomeric state in $^{156}_{73}$Ta 83 of 333$^{+25}_{-22}$ ms was obtained in a separate experiment using the same experimental systems with a 102 Pd target. This result was employed to improve the precision of the half-life determined for 156 W, which was measured as 157$^{+57}_{-34}$ ms.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Laser-based conversion electron Mössbauer spectroscopy of 229 ThO 2

The exceptionally low-energy 229 Th nuclear isomeric state is expected to provide several new and powerful applications, including the construction of a robust and portable solid-state nuclear clock, perhaps contributing to a redefinition of the second, exploration of nuclear superradiance and tests of fundamental physics. Further, analogous to the capabilities of traditional Mössbauer spectroscopy, the sensitivity of the nucleus to its environment can be used to realize laser Mössbauer spectroscopy and, with it, new types of strain and temperature sensors and a new probe of the solid-state environment, all with excellent sensitivity. However, current models for examining the nuclear transition in a solid require the use of a high-bandgap, vacuum ultraviolet (VUV) transmissive host, severely limiting the applicability of these techniques. Here we report the first, to the authors’ knowledge, demonstration of laser-induced conversion electron Mössbauer spectroscopy (CEMS) of the 229 Th isomer in a thin ThO 2 sample whose bandgap (approximately 6 eV) is considerably smaller than the nuclear isomeric state energy (8.4 eV). Unlike fluorescence spectroscopy of the 229 Th isomeric transition, this technique is compatible with materials whose bandgap is less than the nuclear transition energy, opening a wider class of systems to study and the potential of a conversion-electron-based nuclear clock.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Exploration for astromers near 132 Sn with the Canadian Penning Trap

Nuclear isomers can have significant impacts on astrophysical nucleosynthesis processes, with recent efforts demonstrating that the population of isomeric states with different half-lives may require separate treatment in reaction networks to accurately capture the differences in heating or in identifiable electromagnetic signals. Several potential so-called “astromers” in tin and antimony isotopes near doubly magic 132 Sn were identified and direct mass measurements of their ground and isomeric states were performed with the Canadian Penning Trap at Argonne National Laboratory's CARIBU facility, and their impact on astrophysical reaction rates and in reaction networks was calculated. Finally, it was found that 129⁢𝑔,𝑚 Sn , with measured mass excesses of −80593.2⁢(25) and −80557.4⁢(25) keV, respectively, and an excitation energy of 35.8(35) keV, behaves as an astromer during neutron capture in the 𝑖-process and in the 𝑟-process.

isomer decays↗