Search results for "decay"
showing 10 items of 2087 documents
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.
Two-neutrino ββ decay to excited states. The 0+ → 2+ decay of 136Xe
1993
Abstract A method to calculate the two-neutrino double beta decay (2vββ) to one-phonon excited states is presented. The formalism, which is based on the quasiparticle random phase approximation, is applied to the description of the 2vββ transition 136Xe (0 g.e. + ) → 136 Ba (2 1 + ). It is shown that the participant matrix element is not suppressed by the inclusion of renormalized particle-particle interactions.
Calculation of allowed and first-forbidden beta-decay transitions of odd-odd nuclei
1993
Abstract A method for calculating the β − and β + EC transitions from an odd-odd nucleus to the excited states of the adjacent even-even nucleus is presented. The beta transitions are treated combining the charge-conserving and the charge-changing mode of the quasi-particle random- phase approximation assuming a common vacuum. The beta-decay transitions are treated in their allowed and first-forbidden approximations, including also the ground-state transition. As a test case of the present formalism, detailed beta-decay properties of the following odd-odd-to-even-even transitions have been calculated and compared with experiment: the β − decay transitions 136 I (2 − )→ 136 Xe (J π ) and 136…
Quasiparticle alignments andα-decay fine structure of175Pt
2014
Excited states and decay properties of ${}^{175}$Pt have been investigated using the ${}^{92}$Mo${(}^{86}\mathrm{Sr},2pn)$ fusion-evaporation reaction. The JUROGAM I $\ensuremath{\gamma}$-ray spectrometer and the GREAT spectrometer were used in conjunction with the gas-filled recoil separator RITU for the measurement of the radiation at the target and focal plane positions, respectively. Two new band structures, assigned to be based on the ${I}^{\ensuremath{\pi}}=({{}^{7}{/}_{2}}^{\ensuremath{-}})$ ground state in ${}^{175}$Pt, have been established and the known yrast band has been extended up to ${I}^{\ensuremath{\pi}}=({{}^{49}{/}_{2}}^{+})$. Rotational properties of the excited states i…
Alpha decay of the new isotopes207, 208Ac
1994
Two new neutron-deficient isotopes207,208Ac have been produced in fusion reactions with 5.2–5.6 MeV/nucleon40Ar ions on175Lu and identified on the basis of genetic correlations. The fusion evaporation products were separated on-line using a gas-filled magnetic recoil separator. The alpha energy and half-life of208Ac were determined to be (7572±15) keV and (95 −16 +24 ) ms, respectively. A new alpha line with a half-life of (25 −5 +9 ) ms and an energy of (7758±20) keV is assigned to the decay of an isomeric state in208Ac. Another new activity with a half-life of (22 −9 +40 ) ms and an alpha energy of (7712±25) keV is assigned to207Ac.
Coulomb shifts and shape changes in the mass 70 region
2007
The technique of recoil beta tagging has been developed which allows prompt gamma decays in nuclei from excited states to be correlated with electrons from their subsequent short-lived beta decay. This technique is ideal for studying nuclei very far from stability and improves in sensitivity for very short-lived decays and for high decay Q-values. The method has allowed excited states in 78Y to be observed for the first time, as well as an extension in the knowledge of T=1 states in 74Rb. From this new information it has been possible to compare Coulomb energy differences (CED) between T=1 states in 70Br/70Se, 74Rb/74Kr, and 78Y/78Sr. The A=70 CED exhibit an anomalous behavior which is inco…
Testable baryogenesis in seesaw models
2016
We revisit the production of baryon asymmetries in the minimal type I seesaw model with heavy Majorana singlets in the GeV range. In particular we include "washout" effects from scattering processes with gauge bosons, Higgs decays and inverse decays, besides the dominant top scatterings. We show that in the minimal model with two singlets, and for an inverted light neutrino ordering, future measurements from SHiP and neutrinoless double beta decay could in principle provide sufficient information to predict the matter-antimatter asymmetry in the universe. We also show that SHiP measurements could provide very valuable information on the PMNS CP phases.
Nuclear matrix elements of ββ decay from β-decay data
2005
Abstract The evaluation of the nuclear matrix elements (NME) of the two-neutrino double beta ( 2 ν β β ) decay and neutrinoless double beta ( 0 ν β β ) decay using the proton–neutron quasiparticle random-phase approximation (pnQRPA) is addressed. In particular, the extraction of a proper value of the proton–neutron particle–particle interaction parameter, g pp , of this theory is analyzed in detail. Evidence is shown, that it can be misleading to use the experimental half-life of the 2 ν β β decay to extract a value for g pp . Rather, arguments are given in favour of using the available data on single beta decay for this purpose.
Investigation of the decay of to excited states in
1996
The two-neutrino mode of double beta decay of is investigated both theoretically and experimentally. The calculations, using the quasiparticle random phase approximation approach, show that for the detection of transitions to the two first excited states in the daughter nuclide will be possible in the very near future. On the experimental side, new, most stringent limits on half-lives for the double beta decay of to excited states in have been obtained with a `well-type' germanium detector. They range between and years (90% CL).
Level structure of120Sn from the decay of120In and120Sb isomers
1971
Gamma rays in the decay of the 3.2 s (1+) and 44 s (4, 5+)120In isomers and the 15.9 min (1+) and 5.8 d (8−)120Sb isomers have been investigated using Ge(Li) spectrometers and prompt and delayed Ge(Li)-NaI(Tl) coincidence techniques. The constructed level scheme of120Sn contains 18 levels at the following energies (keV): 0 (0+), 1171.6 (2+), 1875.6 (0+), 2096.9 (1, 2, 3), 2160.7 (0+), 2195.0 (4+), 2284.8 (5−), 2355.6 (2+), 2421.2 (1, 2, 3), 2466.3 (4+), 2482.1 (7−), 2643.5 (4+), 3058.6 (4+), 3179.7 (4+), 3349.9 (3, 4+), 3440 (3, 4+), 3447.6 (5, 6+) and 3777 (4+). The levels are compared with the levels obtained from recent charged-particle reaction studies and the structure of120Sn is brief…