Search results for "decay"
showing 10 items of 2087 documents
Electromagnetic fission of $^{238}$U at 600 and 1000 MeV per nucleon
1995
Electromagnetic fission of238U projectiles at E/A =600 and 1000 MeV was studied with the ALADIN spectrometer at the heavy-ion synchrotron SIS. Seven different targets (Be, C, Al, Cu, In, Au and U) were used. By considering only those fission events where the two charges added up to 92, most of the nuclear interactions were excluded. The nuclear contributions to the measured fission cross sections were determined by extrapolating from beryllium to the heavier targets with the concept of factorization. The obtained cross sections for electromagnetic fission are well reproduced by extended Weizsacker-Williams calculations which include E1 and E2 excitations. The asymmetry of the fission fragme…
Mass and charge distributions in the very asymmetric mass region of the neutron induced fission of
2001
Abstract The mass-separator Lohengrin was used to measure the yields of the light fission products with A=74−85 and their nuclear charge and kinetic energy distributions from the odd- Z compound nucleus 239 Np ∗ formed by double capture of thermal neutrons. The mass yield distribution reveals an influence of the fragment shell with N=50 affecting also the nuclear charge and kinetic energy distributions. An odd–even effect for protons is found in the very asymmetric mass division, increasing from 4% to 35% with increasing fission asymmetry. This is in contrast to findings in normal asymmetric fission (region of high fission yields) where no odd–even effect for protons was observed. An odd–ev…
Cross section limits for theCm248(Mg25,4n−5n)Hs268,269reactions
2009
We report on an attempt to produce and detect $^{268}\mathrm{Hs}$ and $^{269}\mathrm{Hs}$ in the nuclear fusion reaction $^{25}\mathrm{Mg}+^{248}\mathrm{Cm}$ using the gas phase chemistry apparatus COMPACT. No decay chains attributable to the decay of hassium isotopes were observed during the course of this experiment. From the nonobservation of $^{269}\mathrm{Hs}$ we derive a cross section limit of 0.4 pb (63% confidence limit) for the reaction $^{248}\mathrm{Cm}(^{25}\mathrm{Mg},4n)^{269}\mathrm{Hs}$ at a center-of-target beam energy of 140 MeV. The evaluated cross section limit for the $^{248}\mathrm{Cm}(^{25}\mathrm{Mg},5n)^{268}\mathrm{Hs}$ reaction depends on the assumed half-life of …
Structures ofPo201andRn205from EC/β+-decay studies
2010
Several low-lying excited states in {sub 86}{sup 205}Rn{sub 119} and {sub 84}{sup 201}Po{sub 117} were identified for the first time following EC/{beta}{sup +} decay of {sup 205}Fr and {sup 201}At, respectively, using {gamma}-ray and conversion electron spectroscopy at the CERN isotope separator on-line (ISOLDE) facility. The EC/{beta}{sup +} branch from {sup 205}Fr was measured to be 1.5(2)%. The excited states of the daughter nuclei are understood in terms of the odd nucleon coupling to the neighboring even-even core. The neutron single-particle energies of the p{sub 3/2} orbital relative to the f{sub 5/2} ground state in {sup 205}Rn, and the f{sub 5/2} orbital relative to the p{sub 3/2} …
Levels of118Sn populated in the decay of118In and118Sb isomers
1970
Gamma-rays in the disintegration of 5.0 s (1+), 8.5 s (7−, 8−), and 4.4 min (4+, 5+)118In isomers and of 3.5 min (1+) and 5.1 h (8−)118Sb isomers have been investigated using Ge(Li) detectors and Ge(Li)-NaI(Tl) coincidence spectrometers. The decay schemes of these isomers have been constructed incorporating 17 levels in the product nucleus,118Sn, at the following energies (in keV): 0 (0+), 1229.5 (2+), 1757.5 (0+), 2043.1 (2+), 2056.4 (0+), 2280.3 (4+), 2321.3 (5−), 2326.4 (1+, 2+), 2402.7 (4+), 2488.8 (4+), 2496.5 (0+), 2575.2 (7−), 2677.3, 2733.7 (2+), 2929.8, 2963.5 (4+), and 3137.1 (0+). The structure of118Sn is briefly discussed in view of results from recent quasiparticle-model calcul…
Beta decay of 108Mo and of neighbouring even Mo-isotopes
1995
Abstract A combination of the proton-induced fission of 238 U and the on-line mass separation based on the ion-guide technique has been applied in the study of neutron-rich Mo-isotopes. The decays of 106,108 Mo have been studied by using gamma-, beta-, X-ray and conversion-electron spectroscopy. The decay scheme of 106 Mo has been revised and a beta-decay half-life of 8.73(12) s has been measured for this nucleus. A beta-decay half-life of 1.09(2) s and a decay energy of 5120(40) keV have been measured for 108 Mo. The decay scheme of 108 Mo has been constructed and altogether 29 new transitions have been placed in the decay scheme. The beta-decay strengths of 102,104,106,108 Mo have been de…
Study of the neutron-rich nuclei with $N$ = 21, $^{35}$Si and $^{33}$Mg, by beta decay of $^{35}$Al and $^{33}$Na
2000
Abstract The first information on the level structure of the N =21 nuclei, 35 Si and 33 Mg, has been obtained by the beta decay study of 35 Al and 33 Na, produced by fragmentation of an UC target with 1.4 GeV protons at CERN/ISOLDE. The experimental technique involved β – γ , β – γ – γ , and β –n– γ coincidences, neutron spectra being obtained by time of flight measurements. Gamma detection was made either using large Ge counters or small BaF 2 scintillators (for lifetime measurements). In the case of the 35 Al decay, ( T 1/2 =41.6(2.2) ms), a simple structure has been found for the level scheme of 35 Si ( Z =14, N =21) which has been interpreted with the level sequence : 7/2 − , 3/2 − and …
Measurement of the IAS resonance strength in 23Mg
2000
Abstract Beta decay of 23 Al to excited states in 23 Mg has been studied using low-energy proton and high-energy gamma-ray detection combined with ion-guide-based on-line mass separation. For the first time, a T =3/2 isobaric analogue state, at 7801(2) keV, was observed to decay by both proton and gamma emission, with a proton branching of 0.17(8)%. The deduced resonance strength ωγ =2.2(10) meV is in agreement with upper limits reported from 22 Na(p, γ ) reaction studies. Shell-model calculations are incorporated.
Decay of aπh11/2⊗νh11/2microsecond isomer in61136Pm75
2008
An experiment has been performed to populate several extremely neutron-deficient nuclei around the mass-140 region of the nuclear chart, using a beam of {sup 54}Fe on a {sup 92}Mo target at an energy of 315 MeV. Analysis of these data using recoil-isomer tagging has established that the yrast {pi}h{sub 11/2} x {nu}h{sub 11/2},J{sup {pi}}=(8{sup +}), bandhead state in {sup 136}Pm is isomeric with a half-life of 1.5(1) {mu}s. This isomeric state decays via a 43-keV, probable-E1 transition to a J{sup {pi}}=(7{sup -}) state. Consideration of the theoretical Nilsson orbitals near the Fermi surface suggests that the J{sup {pi}}=(8{sup +}) state has a {nu}h{sub 11/2}[505](11/2){sup -} x {pi}h{sub …
Is the single-state dominance realized in double-β-decay transitions?
1998
In the single-state-dominance hypothesis (SSDH) the decay rate of the two-neutrino double-\ensuremath{\beta} decay to the final ground state is solely determined by virtual single-\ensuremath{\beta}-decay transitions via the ${1}^{+}$ ground state of the intermediate nucleus. A very important consequence the SSDH will be that some of nonaccelerator measurements of double-\ensuremath{\beta}-decay observables could be circumvented by single-\ensuremath{\beta}-decay measurements. To assess the validity of the SSDH, we have carried out a theoretical analysis of all double-\ensuremath{\beta}-decay transitions where the spin-parity of the ground-state of the intermediate nucleus is ${1}^{+}$. The…