المؤلفون: Albertsson, M., Carlsson, B. G., Døssing, T., Randrup, J., Rudolph, D., Åberg, S.

مصطلحات موضوعية: Nuclear Theory

الوصف: Within the Langevin framework, we investigate the dynamics of the fusion process for production of transfermium elements in reactions of $^{48}$Ca, $^{50}$Ti, $^{54}$Cr, and $^{58}$Fe with $^{208}$Pb. After the reacting nuclei have made contact, the early dynamical stage is dominated by the dissipation of the initial radial kinetic energy, while the subsequent shape evolution is diffusive. The probability for surmounting the inner barrier and forming a compound system is obtained by simulating the evolution as a Metropolis random walk in a five-dimensional potential-energy landscape. Good agreement with the available data is obtained, especially for the maximal formation probability.
Comment: 10 pages, 10 figures

الوصول الحر: http://arxiv.org/abs/2406.05330Test

المؤلفون: Døssing, T., Åberg, S., Albertsson, M., Carlsson, B. G., Randrup, J.

المصدر: Physical Review C. 109(3)

مصطلحات موضوعية: Naturvetenskap, Fysik, Subatomär fysik, Natural Sciences, Physical Sciences, Subatomic Physics

الوصف: We suggest that the angular momentum in fission fragments is generated by statistical excitation at scission. The magnitude of the angular momentum is determined by excitation energy and shell structure in the level density. Treating the prescission shape evolution as a diffusive process, implemented as a Metropolis walk on a five-dimensional potential-energy surface, the average magnitudes of the fission fragment angular momenta are calculated for U235(nth,f), assuming that they are perpendicular to the fission axis. The sawtooth behavior of the average angular momentum magnitude as function of mass number is discussed in connection with the similar observed behavior of the average neutron multiplicity, and a good understanding is achieved. The magnitudes of the angular momenta of light and heavy fragments are found to have a weak negative correlation, in accordance with recent experimental results. This correlation arises from the microcanonical sharing of excitation energy by the fragments at scission, where each energy provides a distribution of angular momenta.

الوصول الحر: https://lup.lub.lu.se/record/fa138f47-d918-47b0-a35f-b61fc371385dTest
http://dx.doi.org/10.1103/PhysRevC.109.034615Test

المؤلفون: Severyukhin A.P., Arsenyev N.N., Borzov I.N., Nazmitdinov R.G., Åberg S.

المصدر: EPJ Web of Conferences, Vol 194, p 02008 (2018)

مصطلحات موضوعية: Physics, QC1-999

الوصف: The β-decay rates of 60Ca have been studied within a microscopic model, which is based on the Skyrme interaction T45 to construct single-particle and phonon spaces. We observe a redistribution of the Gamow–Teller strength due to the phonon-phonon coupling, considered in the model. For 60Sc, the spin-parity of the ground state is found to be 1+. We predict that the half-life of 60Ca is 0.3 ms, while the total probability of the βxn emission is 6:1%. Additionally, the random matrix theory has been applied to analyze the statistical properties of the 1+ spectrum populated in the β-decay to elucidate the obtained results.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2100-014XTest

الوصول الحر: https://doaj.org/article/b6498e393e694768b43294803315bc74Test

المؤلفون: Albertsson, M, Carlsson, BG, Døssing, T, Möller, P, Randrup, J, Åberg, S

المصدر: Physical Review C. 104(6)

مصطلحات موضوعية: Nuclear and Plasma Physics, Synchrotrons and Accelerators, Physical Sciences, Nuclear and plasma physics

الوصف: The so-called super-short fission mode, in which a nucleus divides nearly symmetrically into two unusually energetic fragments, competes favorably with the standard asymmetric fission mode for spontaneous fission of a limited number of nuclei near Fm264 but it quickly fades away at finite excitations. We investigate the energy-dependent competition between those two fission modes for even fermium isotopes from Fm254 to Fm268, using the Metropolis method to simulate the strongly damped fission dynamics being driven by shape- and energy-dependent level densities. The origin of the super-short mode is discussed and its effects on the fragment mass distribution, the total fragment kinetic energy, and the neutron multiplicity are calculated. Generally good agreement with the available data is obtained.

وصف الملف: application/pdf

الوصول الحر: https://escholarship.org/uc/item/8mg7t84tTest

المؤلفون: Såmark-Roth, A., Cox, D. M., Rudolph, D., Sarmiento, L. G., Albertsson, M., Carlsson, B. G., Egido, J. L., Golubev, P., Heery, J., Yakushev, A., Åberg, S., Albers, H. M., Block, M., Brand, H., Calverley, T., Cantemir, R., Clark, R. M., Düllmann, Ch. E., Eberth, J., Fahlander, C., Forsberg, U., Gates, J. M., Giacoppo, F., Götz, M., Götz, S., Herzberg, R.-D., Hrabar, Y., Jäger, E., Judson, D., Khuyagbaatar, J., Kindler, B., Kojouharov, I., Kratz, J. V., Krier, J., Kurz, N., Lens, L., Ljungberg, J., Lommel, B., Louko, J., Meyer, C.-C., Mistry, A., Mokry, C., Papadakis, P., Parr, E., Pore, J. L., Ragnarsson, I., Runke, J., Schädel, M., Schaffner, H., Schausten, B., Shaughnessy, D. A., Thörle-Pospiech, P., Trautmann, N., Uusitalo, J.

المصدر: Physical Review C. 107(2)

مصطلحات موضوعية: Superheavy elements, Nuclear spectroscopy, Alpha decay, Spontaneous fission, E0 decay, Mean field theory, Naturvetenskap, Fysik, Subatomär fysik, Natural Sciences, Physical Sciences, Subatomic Physics

الوصف: Flerovium isotopes (element Z = 114) were produced in the fusion-evaporation reactions 48Ca+242,244Pu and studied with an upgraded TASISpec decay station placed in the focal plane of the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Twenty-nine flerovium decay chains were identified by means of correlated implantation, α decay, and spontaneous fission events. Data analysis aspects and statistical assessments, primarily based on measured rates of various events, which laid the foundation for the comprehensive spectroscopic information on the flerovium decay chains, are presented in detail. Various decay scenarios of an excited state observed in 282Cn are examined in depth with the help of GEANT4 simulations and assessed by predictions of beyond mean-field calculations including triaxial shape degrees of freedom. Previous, revised, and newly derived fission probabilities of even-even superheavy nuclei are compared with various theoretical predictions.

وصف الملف: electronic

الوصول الحر: https://lup.lub.lu.se/record/7bdb9e8a-9ff8-49fd-9ecb-8126a22b3154Test
https://portal.research.lu.se/files/136899316/PhysRevC.107.024301.pdfTest
http://dx.doi.org/10.1103/PhysRevC.107.024301Test

المؤلفون: Cox, D. M., Såmark-Roth, A., Rudolph, D., Sarmiento, L. G., Clark, R. M., Egido, J. L., Golubev, P., Heery, J., Yakushev, A., Åberg, S., Albers, H. M., Albertsson, M., Block, M., Brand, H., Calverley, T., Cantemir, R., Carlsson, B. G., Düllmann, Ch. E., Eberth, J., Fahlander, C., Forsberg, U., Gates, J. M., Giacoppo, F., Götz, M., Götz, S., Herzberg, R.-D., Hrabar, Y., Jäger, E., Judson, D., Khuyagbaatar, J., Kindler, B., Kojouharov, I., Kratz, J. V., Krier, J., Kurz, N., Lens, L., Ljungberg, J., Lommel, B., Louko, J., Meyer, C.-C., Mistry, A., Mokry, C., Papadakis, P., Parr, E., Pore, J. L., Ragnarsson, I., Runke, J., Schädel, M., Schaffner, H., Schausten, B., Shaughnessy, D. A., Thörle-Pospiech, P., Trautmann, N., Uusitalo, J.

المصدر: Physical Review C. 107(2)

مصطلحات موضوعية: Superheavy elements, Nuclear spectroscopy, Alpha decay, Mean field theory, Island of stability, Naturvetenskap, Fysik, Subatomär fysik, Natural Sciences, Physical Sciences, Subatomic Physics

الوصف: Fifteen correlated α-decay chains starting from the odd-A superheavy nucleus 289Fl were observed following the fusion-evaporation reaction 48Ca+244Pu. The results call for at least two parallel α-decay sequences starting from at least two different states of 289Fl. This implies that close-lying levels in nuclei along these chains have quite different spin-parity assignments. Further, observed α-electron and α-photon coincidences, as well as the α-decay fine structure along the decay chains, suggest a change in the ground-state spin assignment between 285Cn and 281Ds. Our experimental results, on the excited level structure of the heaviest odd-N nuclei to date, provide a direct testing ground for theory. This is illustrated by comparison with new nuclear structure calculations based on the symmetry-conserving configuration mixing theory.

وصف الملف: electronic

الوصول الحر: https://lup.lub.lu.se/record/5ee9ca0f-3253-43e2-9534-f63589966e57Test
https://portal.research.lu.se/files/136897865/PhysRevC.107.L021301.pdfTest
http://dx.doi.org/10.1103/PhysRevC.107.L021301Test

المؤلفون: Forsberg U., Rudolph D., Golubev P., Sarmiento L.G., Yakushev A., Andersson L.-L., Nitto A. Di, Düllmann Ch.E., Gates J.M., Gregorich K.E., Gross C.J., Heßberger F.P., Herzberg R.-D., Khuyagbaatar J., Kratz J.V., Rykaczewski K., Schädel M., Åberg S., Ackermann D., Block M., Brand H., Carlsson B.G., Cox D., Derkx X., Eberhardt K., Even J., Fahlander C., Gerl J., Jäger E., Kindler B., Krier J., Kojouharov I., Kurz N., Lommel B., Mistry A., Mokry C., Nitsche H., Omtvedt J.P., Papadakis P., Ragnarsson I., Runke J., Schaffner H., Schausten B., Thörle-Pospiech P., Torres T., Traut T., Trautmann N., Türler A., Ward A., Ward D.E., Wiehl and N.

المصدر: EPJ Web of Conferences, Vol 66, p 02036 (2014)

مصطلحات موضوعية: Physics, QC1-999

الوصف: Nuclides that are considered to be isotopes of element Z = 115 were produced in the reaction 48Ca + 243Am at the GSI Helmholtzzentrum für Schwerionenforschung Darmstadt. The detector setup TASISpec was used. It was mounted behind the gas-filled separator TASCA. Thirty correlated α-decay chains were found, and the energies of the particles were determined with high precision. Two important spectroscopic aspects of the offline data analysis are discussed in detail: the handling of digitized preamplified signals from the silicon strip detectors, and the energy reconstruction of particles escaping to upstream detectors relying on pixel-by-pixel dead-layer thicknesses.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2100-014XTest

الوصول الحر: https://doaj.org/article/64a40b98f43b4473be3279dbcc01c087Test

المؤلفون: Albertsson, M., Carlsson, B. G., Døssing, T., Möller, P., Randrup, J., Åberg, S.

المصدر: Phys. Rev. C 103, 014609 (2021)

مصطلحات موضوعية: Nuclear Theory

الوصف: We calculate neutron multiplicities from fission fragments with specified mass numbers for events having a specified total fragment kinetic energy. The shape evolution from the initial compound nucleus to the scission configurations is obtained with the Metropolis walk method on the five-dimensional potential-energy landscape, calculated with the macroscopic-microscopic method for the three-quadratic-surface shape family. Shape-dependent microscopic level densities are used to guide the random walk, to partition the intrinsic excitation energy between the two proto-fragments at scission, and to determine the spectrum of the neutrons evaporated from the fragments. The contributions to the total excitation energy of the resulting fragments from statistical excitation and shape distortion at scission is studied. Good agreement is obtained with available experimental data on neutron multiplicities in correlation with fission fragments from $^{235}$U(n$_{\rm th}$,f). At higher neutron energies a superlong fission mode appears which affects the dependence of the observables on the total fragment kinetic energy.
Comment: 12 pages, 10 figures

الوصول الحر: http://arxiv.org/abs/2005.09988Test

المؤلفون: Albertsson, M., Carlsson, B. G., Døssing, T., Möller, P., Randrup, J., Åberg, S.

المصدر: Eur. Phys. J. A 56, 46 (2020)

مصطلحات موضوعية: Nuclear Theory

الوصف: Fission-fragment mass and total-kinetic-energy (TKE) distributions following fission of even-even nuclides in the region $74 \leq Z \leq 126$ and $92 \leq N \leq 230$, comprising 896 nuclides have been calculated using the Brownian shape-motion method. The emphasis is the region of superheavy nuclei. To show compatibility with earlier results the calculations are extended to include earlier studied regions. An island of asymmetric fission is obtained in the superheavy region, $106\leq Z\leq114$ and $162\leq N\leq 176$, where the heavy fragment is found to be close to $^{208}$Pb and the light fragment adjusts accordingly. Most experimentally observed $\alpha$-decay chains of superheavy nuclei with $Z > 113 $ terminate by spontaneous fission in our predicted region of asymmetric fission. In these cases, the pronounced large asymmetry is accompanied by a low TKE value compatible with measurements.
Comment: 6 pages, 10 figures, published version in EPJA

الوصول الحر: http://arxiv.org/abs/1910.06030Test

المؤلفون: Såmark-Roth, A, Cox, DM, Rudolph, D, Sarmiento, LG, Carlsson, BG, Egido, JL, Golubev, P, Heery, J, Yakushev, A, Åberg, S, Albers, HM, Albertsson, M, Block, M, Brand, H, Calverley, T, Cantemir, R, Clark, RM, Düllmann, Ch E, Eberth, J, Fahlander, C, Forsberg, U, Gates, JM, Giacoppo, F, Götz, M, Götz, S, Herzberg, R-D, Hrabar, Y, Jäger, E, Judson, D, Khuyagbaatar, J, Kindler, B, Kojouharov, I, Kratz, JV, Krier, J, Kurz, N, Lens, L, Ljungberg, J, Lommel, B, Louko, J, Meyer, C-C, Mistry, A, Mokry, C, Papadakis, P, Parr, E, Pore, JL, Ragnarsson, I, Runke, J, Schädel, M, Schaffner, H, Schausten, B, Shaughnessy, DA, Thörle-Pospiech, P, Trautmann, N, Uusitalo, J

المصدر: Physical Review Letters. 126(3)

مصطلحات موضوعية: Nuclear and Plasma Physics, Synchrotrons and Accelerators, Physical Sciences, Mathematical Sciences, Engineering, General Physics, Mathematical sciences, Physical sciences

الوصف: A nuclear spectroscopy experiment was conducted to study α-decay chains stemming from isotopes of flerovium (element Z=114). An upgraded TASISpec decay station was placed behind the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. The fusion-evaporation reactions ^{48}Ca+^{242}Pu and ^{48}Ca+^{244}Pu provided a total of 32 flerovium-candidate decay chains, of which two and eleven were firmly assigned to ^{286}Fl and ^{288}Fl, respectively. A prompt coincidence between a 9.60(1)-MeV α particle event and a 0.36(1)-MeV conversion electron marked the first observation of an excited state in an even-even isotope of the heaviest man-made elements, namely ^{282}Cn. Spectroscopy of ^{288}Fl decay chains fixed Q_{α}=10.06(1)  MeV. In one case, a Q_{α}=9.46(1)-MeV decay from ^{284}Cn into ^{280}Ds was observed, with ^{280}Ds fissioning after only 518  μs. The impact of these findings, aggregated with existing data on decay chains of ^{286,288}Fl, on the size of an anticipated shell gap at proton number Z=114 is discussed in light of predictions from two beyond-mean-field calculations, which take into account triaxial deformation.

وصف الملف: application/pdf

الوصول الحر: https://escholarship.org/uc/item/38f8f4xxTest