Narrow Results

We have formulated a pocket formula for quadrupole $({\beta }_2)$, octupole $({\beta }_3)$, hexadecapole $({\beta }_4)$ and hexacontatetrapole $({\beta }_6)$ deformation of the nuclear ground state of all isotopes of actinide nuclei (89 $<$Z$<$ 103). This formula is first of its kind and produces a nuclear deformation of all isotopes actinide nuclei 89 $<$Z$<$ 103 with simple inputs of Z and A. Hence, this formula is useful in the fields of nuclear physics to study the structure and interaction of nuclei.

In this paper, a simple semi-empirical formula is proposed for angular momentum-dependent fission barriers of actinides $(89\le Z\le 103)$. This formula produces angular momentum-dependent fission barriers with the simple inputs of atomic number (Z), mass number (A) and angular momentum ($\ell$). The fission barriers produced by the present formula are compared with that of experiments and other models. There is a good agreement between the present formula and experiments. The present formula could be used to evaluate the angular momentum-dependent fission barriers of actinides.

Based on the Unified Fission Model with a Woods–Saxon potential (UFMWS), we have investigated alpha decay and cluster radioactivity of actinide nuclei. To ensure accuracy, we determined the most precise $Q$-values by comparing the results of four nuclear mass models: the liquid drop model (LDM), the DZ28 model, the WS4 model, and the finite range droplet model (FRDM), which were recently improved using a machine learning algorithm. Among these models, it is found that the improved WS4 (IWS4) provides the most accurate $Q$-values, enabling the UFMWS model to effectively reproduce experimental alpha and cluster decay half-lives. Consequently, the UFMWS model using IWS4 $Q$-values was employed to explore various combinations of parent nuclei and alpha particle as well as even–even emitted clusters ranging from Be to Si. The obtained results are consistent with previous study that identified minima in half-lives near corresponding to the doubly magic ${}^{208}$Pb daughter nucleus or its neighboring nuclei. It is found that neutron-deficient parent nuclei generally displayed the shortest half-lives, most of which are within the experimental range. Considering the experimental limitations, cluster decays favorable for measurement in the actinide region were identified. Interestingly, these decays did not involve the most neutron-deficient nuclei.

A large body of experimental work has established the strong kinematical correlation between fission fragments and fission neutrons. Here, we report on the progress of investigations of the potential for strong two neutron correlations arising from the nearly back-to-back nature of the two fission fragments that emit these neutrons in the photo-fission process. In initial measurements, a pulsed electron linear accelerator was used to generate bremsstrahlung photons that impinged upon an actinide target, and the energy and opening angle distributions of coincident neutrons were measured using a large acceptance neutron detector array. A planned comprehensive set of measurements of two neutron correlations in the photo-fission of actinides is expected to shed light on several fundamental aspects of the fission process including the multiplicity distributions associated with the light and heavy fission fragments, the nuclear temperatures of the fission fragments, and the mass distribution of the fission fragments as a function of energy released. In addition to these measurements providing important nuclear data, the unique kinematics of fission and the resulting two neutron correlations have the potential to be the basis for a new tool to detect fissionable materials. A key technical challenge of this program arises from the need to perform coincidence measurements with a low duty factor, pulsed electron accelerator. This has motivated the construction of a large acceptance neutron detector array, and the development of data analysis techniques to directly measure uncorrelated two neutron backgrounds.

The synthesis and reactivity of uranium complexes supported by a bis(aryloxide) cyclam ligand are surveyed. The hemilability of this ligand proved to be particularly appropriate to stabilize highly reactive uranium(III) and uranium(IV) complexes that were able to activate different unsaturated molecules. Of note are the reductive cleavage of azobenzene with the unprecedented formation of a trans-bis(imido) uranium(VI) complex and its reaction with carbon dioxide to generate a trans-oxido-imido uranium(VI) complex and phenyl isocyanate. The formation of a trans-dioxido uranium(VI) (uranyl) complex was also observed in the reaction of uranium(IV) complexes with sodium nitrite. Quantum chemical computations and solution ¹⁵N NMR spectroscopy were employed to evaluate bond covalency in the three {E=U=E}²⁺ complexes (E = O, NR).

²³²Th, ²³⁷Np, ²³⁸U, ²³⁹Pu, and ²⁴¹Am targets were bombarded with proton beam of 26.5 and 62.9 MeV energies. In this contribution some preliminary results are presented and discussed. Comparison with the predictions of the nuclear-reaction model code TALYS is also shown.

Structure properties of many even-even actinides have been calculated using the Gogny D1S force and the Hartree-Fock-Bogoliubov approach as well as the configuration mixing method. Results on rotational states, shape isomers and fission barriers are here discussed.

The first synthetic actinide element, neptunium, was discovered in 1940. The last element of the actinide series, lawrencium, was created for the first time in 1961. These and the nine other intervening elements have added a new dimension to science, technology, industry, medicine, and politics in an extraordinarily short period of time. Each synthetic actinide element from atomic number 93 to atomic number 98 (with the exception of berkelium, atomic number 97) can now be manufactured in essentially any desired quantity, a truly remarkable achievement.

The current status of the application of covariant density functional theory to the description of fission barriers in actinides and superheavy nuclei is reviewed. The achievements and open problems are discussed.