Search results for "isomer decay"
showing 10 items of 19 documents
Total absorption γ -ray spectroscopy of niobium isomers
2019
15 pags. 17 figs., 5 tabs.
First isomeric yield ratio measurements by direct ion counting and implications for the angular momentum of the primary fission fragments
2018
We report the first experimental determination of independent isomeric yield ratios using direct ion counting with a Penning trap, which offered such a high resolution in mass that isomeric states could be separated. The measurements were performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility at the University of Jyvaskyla. The isomer production ratios of Ge-81, Y-96,Y-97 Sn-128(,1)30, and Sb-129 in the 25-MeV proton-induced fission of U-na(t) and Th-232 were studied. Three isomeric pairs (Ge-81, Y-96, and Sb-129) were measured for the first time for the U-na(t)(p, f) reaction, while all the reported yield ratios for the Th-232(p, f) reaction were determined for the first ti…
Isomeric 13/2+ state in 201Fr
2020
We have identified an isomeric state in 201Fr for which we propose a spin and parity of 13/2 +, and interpret it as arising from the π(i13/2 ) configuration. A half-life of 720(40) ns was measured, corresponding to B(M2) = 0.17(2) W.u., in good agreement with those of other 13/2 + → 9/2 − [π(i13/2 ) → π(h9/2 )] transitions observed in other nuclei in the region. The nuclei of interest were produced in a fusion-evaporation reaction and their decay properties were investigated using the GREAT spectrometer at the focal plane of the RITU gas-filled recoil separator. peerReviewed
Prompt and delayed spectroscopy of 203At : Observation of a shears band and a 29/2+ isomeric state
2018
Using fusion-evaporation reactions, a gas-filled recoil separator, recoil-gating technique and recoil-isomer decay tagging technique we have extended the level scheme of 203 At ( N = 118 ) significantly. We have observed an isomeric [ τ = 14.1 ( 3 ) μ s ] state with a spin and parity of 29 / 2 + . The isomeric state is suggested to originate from the π ( h 9 / 2 ) ⊗ ∣ ∣ 202 Po ; 11 − ⟩ coupling, and it is depopulated through 286 keV E 2 and 366 keV E 3 transitions. In addition, we have observed a cascade of magnetic-dipole transitions which is suggested to be generated by the shears mechanism. peerReviewed
Stability of the heaviest elements : K isomer in 250No
2020
Decay spectroscopy of 250No has been performed using digital electronics and pulse-shape analysis of the fast nuclear decays for the first time. Previous studies of 250No reported two distinct fission decay lifetimes, related to the direct fission of the ground state and to the decay of an isomeric state but without the possibility to determine if the isomeric state decayed directly via fission or via internal electromagnetic transitions to the ground state. The data obtained in the current experiment allowed the puzzle to finally be resolved, attributing the shorter half-life of t1/2 = 3.8 ± 0.3 μs to the ground state and the longer half-life t1/2 = 34.9+3.9 −3.2 μs to the decay of an isom…
Isospin symmetry in $B(E2)$ values: Coulomb excitation study of ${}^{21}$Mg
2018
The $T_z$~=~$-\frac{3}{2}$ nucleus ${}^{21}$Mg has been studied by Coulomb excitation on ${}^{196}$Pt and ${}^{110}$Pd targets. A 205.6(1)-keV $\gamma$-ray transition resulting from the Coulomb excitation of the $\frac{5}{2}^+$ ground state to the first excited $\frac{1}{2}^+$ state in ${}^{21}$Mg was observed for the first time. Coulomb excitation cross-section measurements with both targets and a measurement of the half-life of the $\frac{1}{2}^+$ state yield an adopted value of $B(E2;\frac{5}{2}^+\rightarrow\frac{1}{2}^+)$~=~13.3(4)~W.u. A new excited state at 1672(1)~keV with tentative $\frac{9}{2}^+$ assignment was also identified in ${}^{21}$Mg. This work demonstrates large difference…
Decay of a 19− isomeric state in 156Lu
2018
A multiparticle spin-trap isomeric state having a half-life of 179(4) ns and lying 2601 keV above the yrast 10 + state in 156 Lu has been discovered. The 156 Lu nuclei were produced by bombarding isotopically enriched 106 Cd targets with beams of 58 Ni ions, separated in flight using the gas-filled separator RITU and their decays were measured using the GREAT spectrometer. Analysis of the main decay path that populates yrast states observed previously suggests a spin-parity assignment of 19 − for the isomeric state, which is consistent with isomeric states identified in the N = 85 isotones. Comparison with other decay paths in 156 Lu indicates that the [ π h − 1 11 / 2 ⊗ ν h 9 / 2 ] 10 + st…
β Decay of 127Cd and Excited States in 127In
2019
A dedicated spectroscopic study of the β decay of 127Cd was conducted at the IGISOL facility at the University of Jyväskylä. Following high-resolution mass separation in a Penning trap, β−γ−γcoincidences were used to considerably extend the decay scheme of 127In. The β-decaying 3/2+ and 11/2− states in 127Cd have been identified with the 127Cd ground state and the 283-keV isomer. Their respective half-lives have been measured to 0.45(128)s and 0.36(4) s. The experimentally observed βfeeding to excited states of 127In and the decay scheme of 127In are discussed in conjunction with large-scale shell-model calculations. peerReviewed
Identification of a 6.6μs isomeric state in 175Ir
2019
An experiment has been performed to study excited states in the neutron-deficient nucleus 175Ir via the use of the JUROGAM II high-purity germanium detector array and the RITU gas-filled separator at JYFL, Jyväskylä. By using isomer tagging, an isomeric state with a half-life of 6.58(15) μs has been observed in 175Ir for the first time. It has been established that the isomer decays via a 45.2 (E1)–26.1 (M1) keV cascade to new states below the previously reported ground state in 175Ir with Iπ = (5/2−). We now reassign this (5/2−) state to the isomeric state discovered in this study. peerReviewed
Level structure above the 17+ isomeric state in 152 69 Tm83
2018
Excited states above the 17+ isomeric state in the proton-rich nucleus 152Tm were established by employing the recoil-isomer tagging technique. Data were collected using the JUROGAM gamma-ray array and the GREAT spectrometer together with the recoil ion transport unit (RITU) gas-filled recoil separator and analyzed to identify the prompt and delayed γ decays from the levels in 152Tm. Shell-model calculations, either in a large valence space or in a reduced model space with five protons in the π0h11/2 orbital and one neutron in the ν1f7/2 orbital, agree with the observed energies of the yrast levels up to angular momentum J = 21. The observation of near degeneracies in the energy spectrum ca…