High resolution fission probabilities for 229, 230, 232Th(d pf) and 233, 236U(d, pf) reactions
Abstract
The fission probability and the associated fission fragment angular distributions have been measured, with an energy resolution of about 7 keV, for the 229, 230, 232Th(d, pf) and 233, 236U(d, pf) reactions at energies slightly below the top of the fission barrier, with the aim of disclosing new resonant class III states in the third minimum of the fission barrier. Except for 234U, where the existence of numerous well-separated class II states obliterates the observation of the expected class III states, the experimental data indicate the presence of rotational levels with positive and negative parities and a parameter of inertia . In particular, for 231Th where the low-spin members of the rotational bands were previously observed, the , and st now revealed by the (d, pf) reaction.
References (18)
- V.M. Strutinsky
Nucl. Phys.
(1967) - J. Blons et al.
Nucl. Phys.
(1984) - J. Pauwels et al.
Nucl. Instr. Meth.
(1985) - B.B. Back et al.
Nucl. Phys.
(1971) - R. Bengtsson et al.
Nucl. Phys.
(1987) - W.M. Howard et al.
At. Data Nucl. Data Tables
(1980) - P. Möller et al.
- J.F. Berger, private...
- A. Bohr et al.
Cited by (58)
Photonuclear reactions—From basic research to applications
2022, Progress in Particle and Nuclear PhysicsNuclear reactions induced by photons play a vital role for very different aspects of basic research and applications in physics. They are a key ingredient for the synthesis of nuclei in the Universe and provide, due to the selectivity and the model-independence of the reaction mechanism, an extremely valuable probe for researchers. The penetrability of photons in the MeV energy range makes them, in addition, an ideal tool for meeting various societal challenges. The last two decades saw a rapid development of advanced photon sources and detection methods for photonuclear reaction products. Bremsstrahlung and quasi-monoenergetic photon beams with unprecedented intensity and quality combined with state-of-the-art detector technology paved the way for new scientific discoveries and technological applications.
This review focuses on a comprehensive overview of the most important developments since the turn of the millennium restricted to the energy range between atomic and hadronic degrees of freedom. This includes a description of the formalism of photonuclear reactions below and above the particle-separation threshold. The most important techniques used to generate photon beams in the MeV energy range are presented along with selected facilities and instrumentation for diagnostics and for the analysis of photonuclear reactions. The power of photons to probe the atomic nucleus is exemplified in a number of selected examples from fundamental and applied science. New developments, facilities, and ideas promise a vivid future for photonuclear physics.
Nuclear Data Sheets for A=233
2020, Nuclear Data SheetsThe present evaluation of the known A=233 nuclides (233Fr, 233Ra, 233Ac, 233Th, 233Pa, 233U, 233Np, 233Pu, 233Am, 233Cm) and 233Bk represents an update and revision, after 15 years of the previous evaluation of A=233 published by B. Singh and J.K. Tuli (2005Si15). Laboratory identification of 233Bk nuclide is still considered as tentative. Various decay and reaction data are evaluated and compared. Adopted data, levels, gammas, level half-lives, spins, parities, and configuration assignments are provided. For 233Fr, 233Ra, 233Ac, 233Pu, 233Am and 233Cm, information is available for the respective ground states only. The decay schemes from β− decays of 233Fr and 233Ra, and from ε decay of 233Am and 233Cm are unknown, while those from β− decay of 233Ac, and from ε decay of 233Np are considered incomplete. The α decay of 237Np to 233Pa has been studied in detail by many investigators, yet the decay scheme is considered incomplete as several very low-energy transitions are involved, without the knowledge of their intensities, resulting in mismatch of directly measured α feedings and those deduced from γ-transition intensity balances. The decay schemes from α decays of 237Am, 237Cm and 237Cf to respective A=233 daughters are considered incomplete. Particle-transfer and high-spin data are available for 233Th, 233Pa and 233U nuclei, which remain the most extensively studied in this mass chain. However, data for half-lives for the excited states are available only for one level in 233Pa, and for five levels in 233U, thus limiting the knowledge of reduced transition probabilities in this mass chain.
Sensitivity of the nuclear deformability and fission barriers to the equation of state
2018, Nuclear Physics AThe model-dependent analysis of the fission data impacts the extracted fission-related quantities, which are not directly observables, such as the super- and hyperdeformed isomeric states and their energies. We investigated the model dependence of the deformability of a nucleus and its fission barriers on the nuclear equation of state. Within the microscopic–macroscopic model based on a large number of Skyrme nucleon–nucleon interactions, the total energy surfaces and the double-humped fission barrier of 230Th are calculated in a multidimensional deformation space. In addition to the ground-state (GS) and the superdeformed (SD) minima, all the investigated forces yielded a hyperdeformed (HD) minimum. The contour map of the shell-plus-pairing energy clearly displayed the three minima. We found that the GS binding energy and the deformation energy of the different deformation modes along the fission path increase with the incompressibility coefficient , while the fission barrier heights and the excitation energies of the SD and HD modes decrease with it. Conversely, the surface-energy coefficient , the symmetry-energy, and its density-slope parameter decrease the GS energy and the deformation energies, but increase the fission barrier heights and the excitation energies. The obtained deformation parameters of the different deformation modes exhibit almost independence on , and on the symmetry-energy and its density-slope. The principle deformation parameters of the SD and HD isomeric states tend to decrease with .
Modelling Neutron-induced Reactions on <sup>232–237</sup>U from 10 keV up to 30 MeV
2017, Nuclear Data SheetsComprehensive calculations of cross sections for neutron-induced reactions on 232–237U targets are performed in the 10 keV–30 MeV incident energy range with the code EMPIRE–3.2 Malta. The advanced modelling and consistent calculation scheme are aimed at improving our knowledge of the neutron scattering and emission cross sections, and to assess the consistency of available evaluated libraries for light uranium isotopes. The reaction model considers a dispersive optical potential (RIPL 2408) that couples from five (even targets) to nine (odd targets) levels of the ground-state rotational band, and a triple-humped fission barrier with absorption in the wells described within the optical model for fission. A modified Lorentzian model (MLO) of the radiative strength function and Enhanced Generalized Superfluid Model nuclear level densities are used in Hauser-Feschbach calculations of the compound-nuclear decay that include width fluctuation corrections. The starting values for the model parameters are retrieved from RIPL. Excellent agreement with available experimental data for neutron emission and fission is achieved, giving confidence that the quantities for which there is no experimental information are also accurately predicted. Deficiencies in existing evaluated libraries are highlighted.
Nuclear Data Sheets for A = 230
2012, Nuclear Data SheetsThe evaluators present in this publication spectroscopic data and level schemes from radioactive decay and nuclear reactions for all isobars with mass number A=230. This evaluation includes the first experimental evidence of 230Am, produced through the 197Au(40Ar,3n)234Bk (α decay to 230Am) reaction, E(40Ar)=188.4 MeV (2003MoZX).
Microscopic nuclear models for astrophysics: The Brussels BRUSLIB nuclear library and beyond
2006, Nuclear Physics AAstrophysics is in need of a broad variety of nuclear data. This concerns static ground state properties, characteristics of excited nuclei, spontaneous decay properties, or interactions of nuclei with (mainly) nucleons, α-particles or photons. A strong theoretical activity complementing laboratory efforts is also mandatory. A large variety of highly ‘exotic’ laboratory-unreachable nuclei are indeed involved in the astrophysics modelling. Even when laboratory-studied nuclei are considered, theory has very often to be called for.
Mastering the huge volume of nuclear information and making it available in an accurate and usable form for incorporation into astrophysics models is clearly of pivotal importance. The recognition of this necessity has been the driving motivation for the construction of the Brussels library (BRUSLIB) of computed data of astrophysics relevance. It provides an extended information in tabular form on masses, nuclear level densities and partition functions, fission barriers, and thermonuclear reaction rates. In addition of the unprecedented broadness of its scope, BRUSLIB has the unique and most important feature of relying to the largest possible extent on global and coherent microscopic nuclear models.
The models of this sort that we have developed to predict the basic properties of the nuclei and of their interactions are briefly reviewed. The content of the BRUSLIB library that relies on these models is described, as well as a user-friendly nuclear network generator (NETGEN) complementing BRUSLIB. Finally, an application of BRUSLIB and NETGEN to the p-process nucleosynthesis during He detonation in sub-Chandrasekhar CO white dwarfs is proposed.