Search results for "spontaneous fission"
showing 10 items of 42 documents
Direct mass measurements of the heaviest elements with Penning traps
2013
Abstract Penning-trap mass spectrometry (PTMS) is a mature technique to provide atomic masses with highest precision. Applied to radionuclides it enables us to investigate their nuclear structure via binding energies and derived quantities such as nucleon separation energies. Recent progress in slowing down radioactive ion beams in buffer gas cells in combination with advanced ion-manipulation techniques has opened the door to access even the elements above fermium by PTMS. Such elements are produced in complete fusion–evaporation reactions of heavy ions with lead, bismuth, and actinide targets at very low rates. Pioneering high-precision mass measurements of nobelium and lawrencium isotope…
Energy distribution of ternaryαparticles in spontaneous fission ofCf252
2008
The energy distribution of the ternary $\ensuremath{\alpha}$ particles in spontaneous fission of $^{252}\mathrm{Cf}$ was measured. For the first time an energy threshold as low as 1 MeV was reached. The experiment used an array of unshielded silicon detectors measuring energy and time-of-flight (TOF) of ternary particles in coincidence with fission fragments. The TOF resolution of the system was sufficient for clear separation of $^{6}\mathrm{He}$ and tritons from $^{4}\mathrm{He}$. The statistics were adequate to extract the $^{6}\mathrm{He}$/$^{4}\mathrm{He}$ yield ratio. For both $^{4}\mathrm{He}$ and $^{6}\mathrm{He}$, an excess in the yield (as compared to a Gaussian shape) was observe…
Low-spin structure of85Se and theβnbranching of85As
2012
Fission fragments from neutron-induced fission of ${}^{235}$U produced at the high-flux reactor of the Institut Laue-Langevin, Grenoble, were separated with the Lohengrin separator to provide a beam of neutron-rich ${}^{85}\phantom{\rule{-0.16em}{0ex}}$As nuclei. The ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of ${}^{85}\phantom{\rule{-0.16em}{0ex}}$As to ${}^{85}$Se was studied using $\ensuremath{\gamma}$-$\ensuremath{\gamma}$ and $\ensuremath{\beta}$-$\ensuremath{\gamma}$ coincidence techniques. ${}^{85}$Se was also studied using the prompt-$\ensuremath{\gamma}$ coincidence data from spontaneous fission of ${}^{248}$Cm and ${}^{252}$Cf measured with the Eurogam2 and Gammasphere Ge arra…
Beta Decay of 111Tc to 111Ru
1998
The β-decay of the very neutron-rich 111Tc nucleus has been observed. A partial decay scheme of 111Ru is presented, complementing the high-spin levels earlier reported in spontaneous fission work.
Decay properties of265Sg(Z=106)and266Sg(Z=106)
1998
The presently known most neutron-rich isotopes of element 106 (seaborgium, Sg), {sup 265}Sg and {sup 266}Sg, were produced in the fusion reaction {sup 22}Ne+{sup 248}Cm at beam energies of 121 and 123 MeV. Using the On-Line Gas chemistry Apparatus OLGA, a continuous separation of Sg was achieved within a few seconds. Final products were assayed by {alpha}-particle and spontaneous fission (SF) spectrometry. {sup 265}Sg and {sup 266}Sg were identified by observing time correlated {alpha}-{alpha}-({alpha}) and {alpha}-SF decay chains. A total of 13 correlated decay chains of {sup 265}Sg (with an estimated number of 2.8 random correlations) and 3 decay chains of {sup 266}Sg (0.6 random correlat…
Spontaneous fission lifetimes from the minimization of self-consistent collective action
2013
The spontaneous fission lifetime of 264Fm has been studied within nuclear density functional theory by minimizing the collective action integral for fission in a two-dimensional quadrupole collective space representing elongation and triaxiality. The collective potential and inertia tensor are obtained self-consistently using the Skyrme energy density functional and density-dependent pairing interaction. The resulting spontaneous fission lifetimes are compared with the static result obtained with the minimum-energy pathway. We show that fission pathways strongly depend on assumptions underlying collective inertia. With the non-perturbative mass parameters, the dynamic fission pathway become…
STUDIES OF SUPERHEAVY ELEMENTS AT SHIP
2007
An overview of present experimental investigation of superheavy elements is given. The data are compared with theoretical descriptions. Results are reported from an experiment to confirm production of element 112 isotopes in irradiation of 238 UF 4 with 48 Ca . One spontaneous fission event was measured, which agrees with three events of previously measured data which had been assigned to the decay of 283112. However, more experimental work is needed in order to obtain an independent and unambiguous confirmation of previous results.
Search for superheavy elements in damped collisions betweenU238andCm248
1986
Negative results for the production of superheavy elements in damped collisions between $^{238}\mathrm{U}$ projectiles and $^{248}\mathrm{Cm}$ targets are reported. This reaction was believed to permit a closer and more widespread approach to the predicted island of stability near Z=114 and N=184 than any practical fusion reaction. Aqueous and gas phase chemistry techniques were used to isolate superheavy element fractions. The fractions were counted for spontaneous fission activity, fragment kinetic energies, and neutron multiplicities. Cross-section limits for half-lives from hours to several years are g4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}35}$ ${\mathrm{cm}}^{…
New nuclideHa263
1992
A new nuclide $^{263}\mathrm{Ha}$ was produced in the bombardment of a $^{249}\mathrm{Bk}$ target with 93-MeV $^{18}\mathrm{O}$ ions. It was detected via spontaneous fission counting and was shown to have a half-life of about 0.5 min. This activity was also separated from the reaction products by automated rapid chemical separations using cation-exchange chromatography in 0.05M \ensuremath{\alpha}-hydroxyisobutyric acid. After chemical separation, $^{263}\mathrm{Ha}$ was found to decay by spontaneous fission (${57}_{\mathrm{\ensuremath{-}}15}^{+13}$%) and by \ensuremath{\alpha} emission (${\mathit{E}}_{\mathrm{\ensuremath{\alpha}}}$=8.35 MeV, 43%) with a half-life of ${27}_{\mathrm{\ensurem…
Doubly Magic NucleusHs162108270
2006
Theoretical calculations predict $^{270}\mathrm{Hs}$ ($Z=108$, $N=162$) to be a doubly magic deformed nucleus, decaying mainly by $\ensuremath{\alpha}$-particle emission. In this work, based on a rapid chemical isolation of Hs isotopes produced in the $^{26}\mathrm{Mg}+^{248}\mathrm{Cm}$ reaction, we observed 15 genetically linked nuclear decay chains. Four chains were attributed to the new nuclide $^{270}\mathrm{Hs}$, which decays by $\ensuremath{\alpha}$-particle emission with ${Q}_{\ensuremath{\alpha}}=9.02\ifmmode\pm\else\textpm\fi{}0.03\text{ }\text{ }\mathrm{MeV}$ to $^{266}\mathrm{Sg}$ which undergoes spontaneous fission with a half-life of ${444}_{\ensuremath{-}148}^{+444}\text{ }\t…