Search results for "fission"
showing 10 items of 421 documents
Gamow-Teller decay of118Pd and of neighbouring even isotopes of palladium
1989
Neutron-rich isotopes of palladium were produced via the fission of238U by 20 MeV protons. These isotopes were selected using the ion guide-fed on-line mass-separator facility IGISOL at Jyvaskyla. Their decays were studied byβ-ray,γ-ray and conversion-electron spectroscopy. For114Pd and116Pd, the decay schemes established previously were confirmed; additionally multipolarities were determined for a few transitions. In the case of118Pd, only an approximate half-life was known from a previous radiochemical experiment. In the present study, 15 gamma transitions were observed, most of which were placed in a decay scheme. The half-life and the decay energy were found to beT1/2=1.9±0.1 s andQβ=4.…
Beta decay of neutron-rich 118Rh and the lowest excited states in 118Pd
2000
Beta decay of a refractory isotope 118Rh produced in symmetric fission and mass separated by the ion guide technique has been applied for the study of low-lying excited states of 118Pd. The yrast band in 118Pd has been observed up to a 6+ state and the lowest states of the asymmetric γ-band have been identified. The measured half-life of 118Rh is (300±60)ms. The systematics of the excited states in neutron-rich Pd-isotopes implies the saturation towards an O(6) symmetry at N = 70.
Der Zerfall des95Sr
1974
The nuclide95Sr was isolated by chemical separation methods after thermal neutron induced fission of235U. It's decay properties were investigated employing semiconductor spectrometers and coincidence techniques. A half-life of 24.4±0.2 sec was found. Out of 29 gamma rays, 25 transitions representing 97% of the observed gamma-ray intensity were placed in a decay scheme comprising 19 excited states of95Y.
Neutron configurations inPd113
2014
Excited states in $^{113}\mathrm{Pd}$, populated in ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{113}\mathrm{Rh}$ and in spontaneous fission of $^{248}\mathrm{Cm}$ and $^{252}\mathrm{Cf}$, have been studied by means of $\ensuremath{\gamma}$ spectroscopy at the IGISOL facility of Jyv\"askyl\"a University and using large arrays of Ge detectors (Eurogam2 and Gammasphere, respectively). The position of the ${11/2}^{\ensuremath{-}}$ yrast excitation in $^{113}\mathrm{Pd}$, proposed recently at 166.1 keV by other authors, has been corrected to 98.9 keV. The decay of this level has been discussed to explain the observed transition intensities. The ${7/2}^{\ensuremath{-}}$ member of the yras…
Neutron and fragment yields in proton-induced fission of 238U at intermediate energies
2001
The primary fission fragment mass and kinetic energy distributions, and neutron multiplicities as function of fragment mass have been measured in the proton-induced fission of 238 U at energies Ep ¼ 20, 35, 50 and 60 MeV using time-of-flight technique. Pre-scission and post-scission neutron multiplicities have been extracted from double differential distributions. The fragment mass dependence of the post-scission neutron multiplicities reveals the gross nuclear shell structure effect even at the higher proton energies we measured. The yields ofneutron-rich fission products in the fission of 238 U by 25 MeV protons were measured using an ion guide-based isotope separator technique. The resul…
Level lifetimes in neutron-rich Ru isotopes
1995
The neutron-rich Ru isotopes are situated between the strongly deformed Sr-Zr region with axial deformation of f l _ 0.40 [1] and the spherical Cd-Sn region. Evidence for triaxiality of even-even Ru isotopes has been presented in [2-5], and lifetimes of some of their 2 + states have been measured in fission studies [6-9]. It seems, however, that in these experiments the nearly identical energies of the 2 + ---* 0 + transitions in l~ and 11~ could not be separated. Therefore, high-resolution measurements are required in order to perceive the evolution of deformation with increasing neutron number. So far only few measurements by the delayed-coincidence method [10] have been performed on chem…
New results with stored exotic nuclei at relativistic energies
2004
Recently, much progress has been made with stored exotic nuclei at relativistic velocities ( v c = 0.7 ) . Fragments of 208Pb and 209Bi projectiles and fission products from 238U ions were produced, separated in flight with the fragment separator FRS, and injected into the storage-cooler ring ESR for precision measurements. 114 new masses of neutron-deficient isotopes in the lead region have been measured with time-resolved Schottky Mass Spectrometry (SMS). A new isospin dependence of the pairing energy was observed due to the improved mass accuracy of typically 1.5×10-7 (30 keV). New masses of short-lived neutron-rich fission fragments have been obtained with Isochronous Mass Spectrometry …
Systematics of neutron emission probabilities from delayed neutron precursors
1973
A simple correlation based on the gross theory ofβ-decay is derived between the neutron emission probabilitiesPn of delayed neutron precursors, theirβ-decay energies and the neutron binding energies of the daughter nuclei. The correlation is shown to be valid for delayed neutron precursors among the fission products. ThePn-values of several expected but still unidentified neutron precursors are estimated together with their contributions to the delayed neutron groups in thermal-neutron induced fission of235U. Some aspects of theβ-strength function for transitions into highly excited states are discussed.
Microscopic description of complex nuclear decay: multimodal fission
2009
Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.
Excited states in neutron deficient even-even thorium isotopes (218?A?222)
1985
The nuclei218, 220, 222Th were investigated by conversion electron andγ-ray spectroscopy after compound nucleus reactions of14N with209Bi and16, 18O with208Pb. The intenseγ-background from fission was suppressed by spectroscopy of conversion electrons andγ-rays in coincidence with the evaporation residues or theirα-decay. Level schemes were determined for218Th up toIπ=10+ and for220Th and222Th up toIπ=15−. The observed structure of218Th may be explained in the spherical shell model with residual interaction by two neutron excitation. ForN≧130 completely different level schemes are observed showing very intense, collective electric dipole transitions (B(E1)−10−2 W.u.) with energies of typica…