Japan Atomic Energy Agency

About: Japan Atomic Energy Agency is a government organization based out in Tōkai-mura, Japan. It is known for research contribution in the topics: Neutron & Laser. The organization has 7151 authors who have published 17791 publications receiving 259118 citations. The organization is also known as: JAEA & Nihon genshiryoku kenkyū kaihatsu kikō.

Heavy-element fission barriers

Abstract: We present calculations of fission properties for heavy elements. The calculations are based on the macroscopic-microscopic finite-range liquid-drop model with a 2002 parameter set. For each nucleus we have calculated the potential energy in three different shape parametrizations: (1) for 5 009 325 different shapes in a five-dimensional deformation space given by the three-quadratic-surface parametrization, (2) for 10 850 different shapes in a three-dimensional deformation space spanned by epsilon(2), epsilon(4), and gamma in the Nilsson perturbed-spheroid parametrization, supplemented by a densely spaced grid in epsilon(2), epsilon(3), epsilon(4), and epsilon(6) for axially symmetric deformations in the neighborhood of the ground state, and (3) an axially symmetric multipole expansion of the shape of the nuclear surface using beta(2), beta(3), beta(4), and beta(6) for intermediate deformations. For a fissioning system, it is always possible to define uniquely one saddle or fission threshold on the optimum trajectory between the ground state and separated fission fragments. We present such calculated barrier heights for 1585 nuclei from Z=78 to Z=125. Traditionally, actinide barriers have been characterized in terms of a "double-humped" structure. Following this custom we present calculated energies of the first peak, second minimum, and second peak in the barrier for 135 actinide nuclei from Th to Es. However, for some of these nuclei which exhibit a more complex barrier structure, there is no unique way to extract a double-humped structure from the calculations. We give examples of such more complex structures, in particular the structure of the outer barrier region near Th-232 and the occurrence of multiple fission modes. Because our complete results are too extensive to present in a paper of this type, our aim here is limited: (1) to fully present our model and the methods for determining the structure of the potential-energy surface, (2) to present fission thresholds for a large number of heavy elements, (3) to compare our results with the two-humped barrier structure deduced from experiment for actinide nuclei, and (4) to compare to additional fission-related data and other fission models. . (Less)

Sulfur-doping of rutile-titanium dioxide by ion implantation: Photocurrent spectroscopy and first-principles band calculation studies

Abstract: Sulfur (S)-doped titanium dioxide (TiO2) was synthesized by ion implantation and subsequent thermal annealing. The S ions were implanted into the single crystals of rutile TiO2 at a fluence of 8×1015 ions/cm2. According to the results of Rutherford backscattering spectroscopy and ion channeling analysis, the irradiation damage recovered by annealing at 600 °C in air. In the annealed crystal, the S atoms occupied oxygen sites for form Ti-S bonds, as confirmed by x-ray photoelectron spectroscopy. Compared to the pure TiO2, a photocurrent was observed in the lower-energy regions for the S-doped TiO2. Based on the theoretical analyses by the first-principles band calculations using the full potential linearized augmented plane-wave methods within the generalized gradient approximation, the mixing of the S 3p states with the valence band (VB) was found to contribute to the increasing width of the VB. This leads to the band gap narrowing in the S-doped TiO2. Therefore, the photon-to-carrier conversion was induced during irradiation by visible light above 420 nm (<2.9 eV).

Novel features of nuclear forces and shell evolution in exotic nuclei.

Abstract: Novel simple properties of the monopole component of effective nucleon-nucleon interactions are presented, leading to the so-called monopole-based universal interaction. Shell structures are shown to change as functions of $N$ and $Z$, consistent with experiments. Some key cases of this shell evolution are discussed, clarifying the effects of central and tensor forces. The validity of the present tensor force is examined in terms of the low-momentum interaction ${V}_{\mathrm{lowk}}$ and the ${Q}_{\mathrm{box}}$ formalism.