Isomeric Ratios for Nuclei with Z=62–67 and A=142–152 (original) (raw)
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The European Physical Journal A, 2010
The feasibility of measuring g-factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623 keV I π =1 2 + isomer in 192 Pb with τ =1 .57 µs has been produced using the fragmentation of a 1 A GeV 238 U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured values of the lifetime, τ =1 .54(9) µs, and the g-factor, g = −0.175(20), agree with the results of previous investigations using fusion-evaporation reactions.
The European Physical …
The feasibility of measuring g-factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623 keV I π = 12 + isomer in 192 Pb with τ = 1.57 μs has been produced using the fragmentation of a 1 A GeV 238 U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured values of the lifetime, τ = 1.54(9) μs, and the g-factor, g = −0.175(20), agree with the results of previous investigations using fusion-evaporation reactions.
Isomeric decay studies around 204Pt and 148Tb
The European Physical Journal Special Topics, 2007
Relativistic energy projectile fragmentation of 208 Pb has been used to produce a range of exotic nuclei. The nuclei of interest were studied by detecting delayed gamma rays following the decay of isomeric states. Experimental information on the excited states of the neutron-rich N = 126 nucleus, 204 Pt, following internal decay of two isomeric states, was obtained for the first time. In addition, decays from the previously reported isomeric I = 27h and I = (49/2)h states in 148 Tb and 147 Gd, respectively, have been observed. These isomeric decays represent the highest spin discrete states observed to date following a projectile fragmentation reaction, and opens further the possibility of doing 'high-spin physics' using this technique.
Journal of Physics G: Nuclear and Particle Physics, 2002
We report the first g factor measurement on microsecond isomers of neutronrich nuclei produced in projectile-fragmentation reactions at intermediate energies. The nuclides in the vicinity of 68 Ni were produced and spin oriented following the fragmentation of a 76 Ge, 61.4 MeV u −1 beam at GANIL. The LISE spectrometer was used to select the nuclei of interest. The time-dependent perturbed angular distribution (TDPAD) method was applied in combination with the heavy-ion-gamma correlation technique to measure the g factors of 69m Cu (J π = 13/2 + , T 1/2 = 350 ns) and 67m Ni (J π = 9/2 + , T 1/2 = 13.3 µs). Specific details of the experimental technique and the comparison of the results (|g( 69m Cu)| = 0.225(25) and |g( 67m Ni)| = 0.125(6)) with theoretical calculations are discussed. These results provide another indication of the importance of proton excitations across the Z = 28 shell gap.
Neutron-deficient N≈126 nuclei produced in 238U fragmentation: population of high-spin states
2006
The population of metastable states produced in relativistic-energy fragmentation of a 238U beam has been measured. For states with high angular momentum, I=17ℏ and I=21.5ℏ, a higher population than expected has been observed, with the discrepancy increasing with angular momentum. By considering two sources for the angular momentum, related to single-particle and collective motions, a much improved description of the
ISOMER YIELD RATIOS OF FISSION FRAGMENTS 133 Te, 134 I, 135 Xe IN (γ, f),(γ, nf) REACTIONS ON 235 U
Isomeric yield ratios of fission fragments 133 Te, 134 I, 135 Xe in (γ, f), (γ, nf) reactions on 235 U were measured. The contributions to the isomeric yields from nuclei of isobaric chains due to β-decay were taken into consideration. The sample was irradiated by bremsstrahlung of microtron M-30 (Institute of Electron Physics, Uzhgorod, Ukraine) with 17 MeV end point energy. The average angular momenta of the primary fragments were determined with the use of these data. The codes TALYS 1.4 and EMPIRE 3.2 were applied in the calculations. The effect of different expressions for the radiative strength functions and nuclear level densities on average angular momenta was studied.
Isomer decay tagging in the heavy nuclei: Ra 210 and Ra 209
Physical Review C, 2004
Excited states in 210 Ra and 209 Ra were populated using the 184 W͑ 30 Si, xn͒ reaction at 148 MeV beam energy. Fusion evaporation recoils were selected using the gas-filled spectrometer, SASSYER. Prompt ␥ rays were detected using Compton-suppressed Ge detectors from the YRAST Ball array surrounding the target. Delayed ␥ rays, following isomeric decays, were detected at the focal plane of SASSYER with a smaller array of Ge detectors. The decay energy and lifetime for the 8 + ͑h 9/2 ͒ n isomer of 210 Ra were determined; values for the yrast B͑E2;8 + → 6 + ͒ in 210 Ra and neighboring nuclei are interpreted within the seniority scheme. This isomer was also used to select ␥-rays deexciting levels above the isomeric state in 210 Ra. In addition, transitions in 209 Ra were identified for the first time. Two high-spin isomers are suggested to exist in this isotope.
Isomeric Decays in Neutron-Rich W, Os and Pt Nuclei
Progress of Theoretical Physics Supplement, 2002
Relativistic energy fragmentation of a 1 GeV/nucleon 208 Pb beam was used to populate a wide range of nuclei on both sides of the valley of β-stability. The structure of these nuclei was studied by the identification of discrete γ-ray transitions depopulating isomeric states with lifetimes in the nano-to millisecond range. Highlights of the experiment include the first observation of γ-ray transitions in the neutron-rich nuclei 188 Ta, 190 W, 192 Re, 195 Os, 197,198 Ir, 201,202 Pt. The yrast states in 190 W and 202 Pt as well as the decay out from 10-20 ns isomers in 202,201 Pt and 195 Os are discussed. The observation of the previously reported isomeric K = 35 2 states in 175 Hf, 179 W and 181 Re represents the highest discrete spin states observed to date following a projectile fragmentation reaction.
Observation of a dramatic hindrance of the nuclear decay of isomeric states for fully ionized atoms
Physics Letters B, 2003
The half-lives of isomeric states of fully ionized 144 Tb, 149 Dy and 151 Er have been measured. These nuclides were produced via fragmentation of about 900 MeV/u 209 Bi projectiles, separated in flight with the fragment separator (FRS) and stored in the cooler ring (ESR). The decay times of the cooled fragments have been measured with time-resolved Schottky spectrometry. We observed for the first time drastic increases of the half-lives of bare isomers by factors of up to 30 compared to their neutral counterparts. This is due to the exclusion of the strong internal conversion and electron-capture channels in the radioactive decay of these bare nuclei. The experimental results are in good agreement with theoretical calculations.