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202 results on '"S. Siem"'

1. Experimental observation of the M1 scissors mode in 254No

Author

F.L. Bello Garrote, A. Lopez-Martens, A.C. Larsen, I. Deloncle, S. Péru, F. Zeiser, P.T. Greenlees, B.V. Kheswa, K. Auranen, D.L. Bleuel, D.M. Cox, L. Crespo Campo, F. Giacoppo, A. Görgen, T. Grahn, M. Guttormsen, T.W. Hagen, L. Harkness-Brennan, K. Hauschild, G. Henning, R.-D. Herzberg, R. Julin, S. Juutinen, T.A. Laplace, M. Leino, J.E. Midtbø, V. Modamio, J. Pakarinen, P. Papadakis, J. Partanen, T. Renstrøm, K. Rezynkina, M. Sandzelius, J. Sarén, C. Scholey, S. Siem, J. Sorri, S. Stolze, and J. Uusitalo

Subjects
Scissors mode, γ-strength function, Transfermium nuclides, Physics, QC1-999
Abstract

We present the first experimental evidence of the scissors mode in the superheavy nucleus 254No produced in the 208Pb(48Ca, 2nγ))254No reaction. The spectrum of γ rays emitted by the excited 254No nuclei shows an enhanced γ-ray yield for transition energies of ≈2.5 MeV. By measuring the linear polarization properties of the emitted γ rays, we confirm that the transitions in the enhancement region are predominantly of magnetic-dipole character, characteristic for the scissors mode. To further characterize the enhanced γ-ray yield, simulations of the electromagnetic decay of 254No were performed. The observed enhancement is reproduced by including an M1 component in the γ strength function with total strength B(M1↑)=11.8(19)μN2. This is in good agreement with the integrated M1 strength from sum-rule estimates and new calculations within the quasi-particle random-phase approximation presented here. Our results provide a stringent test of phenomenological formulae for the scissors mode currently used in stellar nucleosynthesis calculations. We find that those formulae are not satisfactory, and we recommend using sum-rule estimates assuming a rigid-body moment of inertia instead for describing the scissors mode in superheavy nuclei.

Published
2022
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2. Investigating the predicted breathing-mode excitation of the Hoyle state

Author

K.C.W. Li, F.D. Smit, P. Adsley, R. Neveling, P. Papka, E. Nikolskii, J.W. Brümmer, L.M. Donaldson, M. Freer, M.N. Harakeh, F. Nemulodi, L. Pellegri, V. Pesudo, M. Wiedeking, E.Z. Buthelezi, V. Chudoba, S.V. Förtsch, P. Jones, M. Kamil, J.P. Mira, G.G. O'Neill, E. Sideras-Haddad, B. Singh, S. Siem, G.F. Steyn, J.A. Swartz, I.T. Usman, and J.J. van Zyl

Subjects
Nuclear structure, Nuclear astrophysics, Cluster models, Nuclear reactions, Collective levels, Direct reactions, Physics, QC1-999
Abstract

Knowledge of the low-lying monopole strength in C12—the Hoyle state in particular—is crucial for our understanding of both the astrophysically important 3α reaction and of α-particle clustering. Multiple theoretical models have predicted a breathing mode of the Hoyle State at Ex≈9 MeV, corresponding to a radial in-phase oscillation of the underlying α clusters. The C12(α,α′)C12 and C14(p,t)C12 reactions were employed to populate states in 12C in order to search for this predicted breathing mode. A self-consistent, simultaneous analysis of the inclusive spectra with R-matrix lineshapes, together with angular distributions of charged-particle decay, yielded clear evidence for excess monopole strength at Ex≈9 MeV which is highly collective. Reproduction of the experimentally observed inclusive yields using a fit, with consistent population ratios for the various broad states, required an additional source of monopole strength. The interpretation of this additional monopole resonance as the breathing-mode excitation of the Hoyle state would provide evidence supporting a D3h symmetry for the Hoyle state itself. The excess monopole strength may complicate analysis of the properties of the Hoyle state, modifying the temperature dependence of the 3α rate at T9≳2 and ultimately, the predicted nucleosynthesis in explosive stars.

Published
2022
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3. Strong enhancement of level densities in the crossover from spherical to deformed neodymium isotopes

Author

M. Guttormsen, Y. Alhassid, W. Ryssens, K.O. Ay, M. Ozgur, E. Algin, A.C. Larsen, F.L. Bello Garrote, L. Crespo Campo, T. Dahl-Jacobsen, A. Görgen, T.W. Hagen, V.W. Ingeberg, B.V. Kheswa, M. Klintefjord, J.E. Midtbø, V. Modamio, T. Renstrøm, E. Sahin, S. Siem, G.M. Tveten, and F. Zeiser

Subjects
Nuclear level density, Oslo method, Shell model Monte Carlo, Mean-field theory, Collective enhancement, Physics, QC1-999
Abstract

Understanding the evolution of level densities in the crossover from spherical to well-deformed nuclei has been a long-standing problem in nuclear physics. We measure nuclear level densities for a chain of neodymium isotopes 142,144−151Nd which exhibit such a crossover. These results represent the most complete data set of nuclear level densities to date for an isotopic chain between neutron shell-closure and towards mid-shell. We observe a strong increase of the level densities along the chain with an overall increase by a factor of ≈150 at an excitation energy of 6 MeV and saturation around mass 150. Level densities calculated by the shell model Monte Carlo (SMMC) are in excellent agreement with these experimental results. Based on our experimental and theoretical findings, we offer an explanation of the observed mass dependence of the level densities in terms of the intrinsic single-particle level density and the collective enhancement.

Published
2021
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4. Proton-dynamic therapy following photosensitiser activation by accelerated protons demonstrated through fluorescence and singlet oxygen production

Author

M. Grigalavicius, M. Mastrangelopoulou, K. Berg, D. Arous, M. Ménard, T. Raabe-Henriksen, E. Brondz, S. Siem, A. Görgen, N. F. J. Edin, E. Malinen, and T. A. Theodossiou

Subjects
Science
Abstract

The authors use accelerated protons on photosensitizers (PS, conventionally excited by light), to generate fluorescence and singlet oxygen which can enhance the efficacy of proton therapy. A pilot study on glioblastoma cells confirms differential cell death upon irradiation in the presence of PS.

Published
2019
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5. Re-estimation of 180Ta nucleosynthesis in light of newly constrained reaction rates

Author

K.L. Malatji, M. Wiedeking, S. Goriely, C.P. Brits, B.V. Kheswa, F.L. Bello Garrote, D.L. Bleuel, F. Giacoppo, A. Görgen, M. Guttormsen, K. Hadynska-Klek, T.W. Hagen, V.W. Ingeberg, M. Klintefjord, A.C. Larsen, P. Papka, T. Renstrøm, E. Sahin, S. Siem, L. Siess, G.M. Tveten, and F. Zeiser

Subjects
Physics, QC1-999
Abstract

Recent measurements of the nuclear level densities and γ-ray strength functions below the neutron thresholds in 180,181,182Ta are used as input in the nuclear reaction code TALYS. These experimental average quantities are utilized in the calculations of the 179,180,181Ta radiative neutron capture cross sections. From the latter, astrophysical Maxwellian-averaged (n,γ) cross sections (MACS) and reaction rates are extracted, which in turn are used in large astrophysical network calculations to probe the production mechanism of 180Ta. These calculations are performed for two scenarios, the s-process production of 180,181Ta in Asymptotic Giant Branch (AGB) stars and the p-process nucleosynthesis of Tam180 in Type-II supernovae. Based on the results from this work, the s-process in stellar evolution is considered negligible in the production of Tam180 whereas 181Ta is partially produced by AGB stars. The new measurements strongly constrain the production and destruction rates of Tam180 at p-process temperatures and confirm significant production of nature's rarest stable isotope Tam180 by the p-process. Keywords: Nuclear level density, γ-ray strength function, (n,γ) cross sections, Maxwellian-averaged cross sections, Nucleosynthesis

Published
2019
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7. Galactic production of 138La: Impact of 138,139La statistical properties

Author

B.V. Kheswa, M. Wiedeking, F. Giacoppo, S. Goriely, M. Guttormsen, A.C. Larsen, F.L. Bello Garrote, T.K. Eriksen, A. Görgen, T.W. Hagen, P.E. Koehler, M. Klintefjord, H.T. Nyhus, P. Papka, T. Renstrøm, S. Rose, E. Sahin, S. Siem, and T. Tornyi

Subjects
Physics, QC1-999
Abstract

The γ-ray strength functions and nuclear level densities of 138La and 139La have been measured below the neutron separation energies. These new data were used to calculate astrophysical Maxwellian-averaged (n,γ) cross-sections to investigate the production and destruction of the p-nucleus 138La in the photodisintegration process. The results confirm the underproduction of 138La in the p-process with respect to the observed abundances and strongly support the ν-process through νe capture on 138Ba as the main contributor to the synthesis of 138La in Type II supernovae. Keywords: γ-ray strength functions, Nuclear level densities, Maxwellian averaged cross-sections

Published
2015
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8. Pygmy dipole resonance in 124Sn populated by inelastic scattering of 17O

Author

L. Pellegri, A. Bracco, F.C.L. Crespi, S. Leoni, F. Camera, E.G. Lanza, M. Kmiecik, A. Maj, R. Avigo, G. Benzoni, N. Blasi, C. Boiano, S. Bottoni, S. Brambilla, S. Ceruti, A. Giaz, B. Million, A.I. Morales, R. Nicolini, V. Vandone, O. Wieland, D. Bazzacco, P. Bednarczyk, M. Bellato, B. Birkenbach, D. Bortolato, B. Cederwall, L. Charles, M. Ciemala, G. De Angelis, P. Désesquelles, J. Eberth, E. Farnea, A. Gadea, R. Gernhäuser, A. Görgen, A. Gottardo, J. Grebosz, H. Hess, R. Isocrate, J. Jolie, D. Judson, A. Jungclaus, N. Karkour, M. Krzysiek, E. Litvinova, S. Lunardi, K. Mazurek, D. Mengoni, C. Michelagnoli, R. Menegazzo, P. Molini, D.R. Napoli, A. Pullia, B. Quintana, F. Recchia, P. Reiter, M.D. Salsac, B. Siebeck, S. Siem, J. Simpson, P.-A. Söderström, O. Stezowski, Ch. Theisen, C. Ur, J.J. Valiente Dobon, and M. Zieblinski

Subjects
Physics, QC1-999
Abstract

The γ decay from the high-lying states of 124Sn was measured using the inelastic scattering of 17O at 340 MeV. The emitted γ rays were detected with high resolution with the AGATA demonstrator array and the scattered ions were detected in two segmented ΔE–E silicon telescopes. The angular distribution was measured both for the γ rays and the scattered 17O ions. An accumulation of E1 strength below the particle threshold was found and compared with previous data obtained with (γ,γ′) and (α,α′γ) reactions. The present results of elastic scattering, and excitation of E2 and E1 states were analysed using the DWBA approach. From this comprehensive description the isoscalar component of the 1− excited states was extracted. The obtained values are based on the comparison of the data with DWBA calculations including a form factor deduced using a microscopic transition density. Keywords: Low-lying electric dipole excitations, 124Sn, Isospin character

Published
2014
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9. Statistical (n,$$\gamma $$) cross section model comparison for short-lived nuclei

Author

R. Lewis, A. Couture, S. N. Liddick, A. Spyrou, D. L. Bleuel, L. Crespo Campo, B. P. Crider, A. C. Dombos, M. Guttormsen, T. Kawano, A. C. Larsen, A. M. Lewis, S. Mosby, G. Perdikakis, C. J. Prokop, S. J. Quinn, T. Renstrøm, and S. Siem

Subjects
Nuclear and High Energy Physics
Abstract

Neutron-capture cross sections of neutron-rich nuclei are calculated using a Hauser–Feshbach model when direct experimental cross sections cannot be obtained. A number of codes to perform these calculations exist, and each makes different assumptions about the underlying nuclear physics. We investigated the systematic uncertainty associated with the choice of Hauser-Feshbach code used to calculate the neutron-capture cross section of a short-lived nucleus. The neutron-capture cross section for $$^{73}\hbox {Zn}$$ 73 Zn (n,$$\gamma $$ γ )$$^{74}\hbox {Zn}$$ 74 Zn was calculated using three Hauser-Feshbach statistical model codes: TALYS, CoH, and EMPIRE. The calculation was first performed without any changes to the default settings in each code. Then an experimentally obtained nuclear level density (NLD) and $$\gamma $$ γ -ray strength function ($$\gamma \hbox {SF}$$ γ SF ) were included. Finally, the nuclear structure information was made consistent across the codes. The neutron-capture cross sections obtained from the three codes are in good agreement after including the experimentally obtained NLD and $$\gamma \hbox {SF}$$ γ SF , accounting for differences in the underlying nuclear reaction models, and enforcing consistent approximations for unknown nuclear data. It is possible to use consistent inputs and nuclear physics to reduce the differences in the calculated neutron-capture cross section from different Hauser-Feshbach codes. However, ensuring the treatment of the input of experimental data and other nuclear physics are similar across multiple codes requires a careful investigation. For this reason, more complete documentation of the inputs and physics chosen is important.

Published
2023

10. Observation of a candidate for the M1 scissors resonance in odd-odd Ho166

Author

F. Pogliano, F. L. Bello Garrote, A. C. Larsen, H. C. Berg, D. Gjestvang, A. Görgen, M. Guttormsen, V. W. Ingeberg, T. W. Johansen, K. L. Malatji, E. F. Matthews, M. Markova, J. E. Midtbø, V. Modamio, L. G. Pedersen, E. Sahin, S. Siem, T. G. Tornyi, and A. S. Voyles

Published
2023

12. Extracting model-independent nuclear level densities away from stability

Author

D. Mücher, A. Spyrou, M. Wiedeking, M. Guttormsen, A. C. Larsen, F. Zeiser, C. Harris, A. L. Richard, M. K. Smith, A. Görgen, S. N. Liddick, S. Siem, H. C. Berg, J. A. Clark, P. A. DeYoung, A. C. Dombos, B. Greaves, L. Hicks, R. Kelmar, S. Lyons, J. Owens-Fryar, A. Palmisano, D. Santiago-Gonzalez, G. Savard, and W. W. von Seeger

Published
2023

15. Indirect measurement of the (n,γ)Sb127 cross section

Author

F. Pogliano, A. C. Larsen, F. L. Bello Garrote, M. M. Bjørøen, T. K. Eriksen, D. Gjestvang, A. Görgen, M. Guttormsen, K. C. W. Li, M. Markova, E. F. Matthews, W. Paulsen, L. G. Pedersen, S. Siem, T. Storebakken, T. G. Tornyi, and J. E. Vevik

Published
2022

16. Interactions between trade wind clouds and local forcings over the Great Barrier Reef: a case study using convection-permitting simulations

Author

W. Zhao, Y. Huang, S. Siems, M. Manton, and D. Harrison

Subjects
Physics, QC1-999, Chemistry, QD1-999
Abstract

Trade wind clouds are ubiquitous across the subtropical oceans, including the Great Barrier Reef (GBR), playing an important role in modulating the regional energy budget. These shallow clouds, however, are by their nature sensitive to perturbations in both their thermodynamic environment and microphysical background. In this study, we employ the Weather Research and Forecasting (WRF) model with a convection-permitting configuration at 1 km resolution to examine the sensitivity of the trade wind clouds to different local forcings over the GBR. A range of local forcings including coastal topography, sea surface temperature (SST), and local aerosol loading is examined. This study shows a strong response of cloud fraction and accumulated precipitation to orographic forcing both over the mountains and upwind over the GBR. Orographic lifting, low-level convergence, and lower troposphere stability are found to be crucial in explaining the cloud and precipitation features over the coastal mountains downwind of the GBR. However, clouds over the upwind ocean are more strongly constrained by the trade wind inversion, whose properties are, in part, regulated by the coastal topography. On the scales considered in this study, the warm-cloud fraction and the ensuant precipitation over the GBR show only a small response to the local SST forcing, with this response being tied to the surface flux and lower troposphere stability. Cloud microphysical properties, including cloud droplet number concentration, liquid water path, and precipitation, are sensitive to the changes in atmospheric aerosol population over the GBR. While cloud fraction shows little responses, a slight deepening of the simulated clouds is evident over the upwind region in correspondence to the increased aerosol number concentration. A downwind effect of aerosol loading on simulated cloud and precipitation properties is further noted.

Published
2024
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17. Multiprobe study of excited states in C12 : Disentangling the sources of monopole strength between the energy of the Hoyle state and Ex=13 MeV

Author

K. C. W. Li, P. Adsley, R. Neveling, P. Papka, F. D. Smit, E. Nikolskii, J. W. Brümmer, L. M. Donaldson, M. Freer, M. N. Harakeh, F. Nemulodi, L. Pellegri, V. Pesudo, M. Wiedeking, E. Z. Buthelezi, V. Chudoba, S. V. Förtsch, P. Jones, M. Kamil, J. P. Mira, G. G. O'Neill, E. Sideras-Haddad, B. Singh, S. Siem, G. F. Steyn, J. A. Swartz, I. T. Usman, and J. J. van Zyl

Published
2022

18. Experimental observation of the M1 scissors mode in $^{254}No$

Author

F.L. Bello Garrote, A. Lopez-Martens, A.C. Larsen, I. Deloncle, S. Péru, F. Zeiser, P.T. Greenlees, B.V. Kheswa, K. Auranen, D.L. Bleuel, D.M. Cox, L. Crespo Campo, F. Giacoppo, A. Görgen, T. Grahn, M. Guttormsen, T.W. Hagen, L. Harkness-Brennan, K. Hauschild, G. Henning, R.-D. Herzberg, R. Julin, S. Juutinen, T.A. Laplace, M. Leino, J.E. Midtbø, V. Modamio, J. Pakarinen, P. Papadakis, J. Partanen, T. Renstrøm, K. Rezynkina, M. Sandzelius, J. Sarén, C. Scholey, S. Siem, J. Sorri, S. Stolze, J. Uusitalo, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), CEA DAM ILE-DE-FRANCE - Bruyères-le-Châtel [Arpajon] (CEA DAM IDF), Département Recherches Subatomiques (DRS-IPHC), Institut Pluridisciplinaire Hubert Curien (IPHC), and Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Nuclear and High Energy Physics, scissors mode, transfermium nuclides, γ-strength function, ddc:530, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], ydinfysiikka
Abstract

Physics letters / B 834, 137479 (2022). doi:10.1016/j.physletb.2022.137479, Published by North-Holland Publ., Amsterdam

Published
2022

19. Evolution of the gamma-ray strength function in neodymium isotopes

Author

M. Guttormsen, K. O. Ay, M. Ozgur, E. Algin, A. C. Larsen, F. L. Bello Garrote, H. C. Berg, L. Crespo Campo, T. Dahl-Jacobsen, F. W. Furmyr, D. Gjestvang, A. Görgen, T. W. Hagen, V. W. Ingeberg, B. V. Kheswa, I. K. B. Kullmann, M. Klintefjord, M. Markova, J. E. Midtbø, V. Modamio, W. Paulsen, L. G. Pedersen, T. Renstrøm, E. Sahin, S. Siem, G. M. Tveten, and M. Wiedeking

Subjects
Nuclear Theory, Astrophysics::High Energy Astrophysical Phenomena, Modes, Dipole, Nuclear Experiment
Abstract

The experimental gamma-ray strength functions (gamma-SFs) of 142,144-151Nd have been studied for gamma-ray energies up to the neutron separation energy. The results represent a unique set of gamma-SFs for an isotopic chain with increasing nuclear deformation. The data reveal how the low-energy enhancement, the scissors mode and the pygmy dipole resonance evolve with nuclear deformation and mass number. The data indicate that the mechanisms behind the low-energy enhancement and the scissors mode are decoupled from each other., Comment: 14 pages and 10 figures

Published
2022

20. Short-term production scheduling with non-triangular sequence-dependent setup times and shifting production bottlenecks

Author

Berkhout, J. (Joost), Pauwels, E.J.E.M. (Eric), Mei, R.D. (Rob) van der, Stolze, J. (Jan), Broersen, S. (Siem), Berkhout, J. (Joost), Pauwels, E.J.E.M. (Eric), Mei, R.D. (Rob) van der, Stolze, J. (Jan), and Broersen, S. (Siem)

Abstract

A novel mathematical model is introduced that allows solving real-life scheduling problems in complex multi-stage machine environment with (i) non-triangular sequence-dependent setup times and (ii) shifting production bottlenecks, both of which are important aspects appearing in varying manufacturing industries. The primary goal is to minimise the tardiness of customer orders, which may consist of multiple production orders each in turn composed of several batches. A secondary objective is to maximise the production capacity utilization as measured by the makespan. The model is elaborated for general animal-feed plants which have to deal with the particular production scheduling problem on a daily basis. Dispatching rules are introduced to enhance the optimization progress. Numerical experiments show that optimising the model leads to schedules that meet the due dates. Moreover, by reducing the mean idle time of production lines with 35.6%, the optimization leads to a makespan reduction of 6.5% on average compared to real-life applied schedules.

Published
2021
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21. Short-term production scheduling with non-triangular sequence-dependent setup times and shifting production bottlenecks

Author

Berkhout, J. (Joost), Pauwels, E.J.E.M. (Eric), Mei, R.D. (Rob) van der, Stolze, J. (Jan), Broersen, S. (Siem), Berkhout, J. (Joost), Pauwels, E.J.E.M. (Eric), Mei, R.D. (Rob) van der, Stolze, J. (Jan), and Broersen, S. (Siem)

Abstract

A novel mathematical model is introduced that allows solving real-life scheduling problems in complex multi-stage machine environment with (i) non-triangular sequence-dependent setup times and (ii) shifting production bottlenecks, both of which are important aspects appearing in varying manufacturing industries. The primary goal is to minimise the tardiness of customer orders, which may consist of multiple production orders each in turn composed of several batches. A secondary objective is to maximise the production capacity utilization as measured by the makespan. The model is elaborated for general animal-feed plants which have to deal with the particular production scheduling problem on a daily basis. Dispatching rules are introduced to enhance the optimization progress. Numerical experiments show that optimising the model leads to schedules that meet the due dates. Moreover, by reducing the mean idle time of production lines with 35.6%, the optimization leads to a makespan reduction of 6.5% on average compared to real-life applied schedules.

Published
2020
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26. Examination of the low-energy enhancement of the γ -ray strength function of Fe 56

Author

M. D. Jones, A. O. Macchiavelli, M. Wiedeking, L. A. Bernstein, H. L. Crawford, C. M. Campbell, R. M. Clark, M. Cromaz, P. Fallon, I. Y. Lee, M. Salathe, A. Wiens, A. D. Ayangeakaa, D. L. Bleuel, S. Bottoni, M. P. Carpenter, H. M. Davids, J. Elson, A. Görgen, M. Guttormsen, R. V. F. Janssens, J. E. Kinnison, L. Kirsch, A. C. Larsen, T. Lauritsen, W. Reviol, D. G. Sarantites, S. Siem, and A. V. Voinov

Published
2018
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29. Anomalies in the Charge Yields of Fission Fragments from the $^{238}$U(n,f) Reaction

Author

J N, Wilson, M, Lebois, L, Qi, P, Amador-Celdran, D, Bleuel, J A, Briz, R, Carroll, W, Catford, H, De Witte, D T, Doherty, R, Eloirdi, G, Georgiev, A, Gottardo, A, Goasduff, K, Hadyńska-Klęk, K, Hauschild, H, Hess, V, Ingeberg, T, Konstantinopoulos, J, Ljungvall, A, Lopez-Martens, G, Lorusso, R, Lozeva, R, Lutter, P, Marini, I, Matea, T, Materna, L, Mathieu, A, Oberstedt, S, Oberstedt, S, Panebianco, Zs, Podolyák, A, Porta, P H, Regan, P, Reiter, K, Rezynkina, S J, Rose, E, Sahin, M, Seidlitz, O, Serot, R, Shearman, B, Siebeck, S, Siem, A G, Smith, G M, Tveten, D, Verney, N, Warr, F, Zeiser, M, Zielinska, Institut de Physique Nucléaire d'Orsay (IPNO), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Laboratoire de physique subatomique et des technologies associées (SUBATECH), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), CEA Cadarache, Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut de Physique Nucléaire d'Orsay ( IPNO ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de physique subatomique et des technologies associées ( SUBATECH ), IMT Atlantique Bretagne-Pays de la Loire ( IMT Atlantique ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Nantes ( UN ), Institut de Recherches sur les lois Fondamentales de l'Univers ( IRFU ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Paris-Saclay, Centre de Sciences Nucléaires et de Sciences de la Matière ( CSNSM ), Direction des Applications Militaires ( DAM ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Centre d'Etudes Nucléaires de Bordeaux Gradignan ( CENBG ), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Centre National de la Recherche Scientifique ( CNRS ), Université de Nantes (UN)-Université de Nantes (UN)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, Physics::Atomic and Molecular Clusters, [ PHYS.NEXP ] Physics [physics]/Nuclear Experiment [nucl-ex], [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract

Fast-neutron-induced fission of 238U at an energy just above the fission threshold is studied with a novel technique which involves the coupling of a high-efficiency γ-ray spectrometer (MINIBALL) to an inverse-kinematics neutron source (LICORNE) to extract charge yields of fission fragments via γ−γ coincidence spectroscopy. Experimental data and fission models are compared and found to be in reasonable agreement for many nuclei; however, significant discrepancies of up to 600% are observed, particularly for isotopes of Sn and Mo. This indicates that these models significantly overestimate the standard 1 fission mode and suggests that spherical shell effects in the nascent fission fragments are less important for low-energy fast-neutron-induced fission than for thermal neutron-induced fission. This has consequences for understanding and modeling the fission process, for experimental nuclear structure studies of the most neutron-rich nuclei, for future energy applications (e.g., Generation IV reactors which use fast-neutron spectra), and for the reactor antineutrino anomaly. ispartof: Physical Review Letters vol:118 issue:22 ispartof: location:United States status: published

Published
2017

31. La 137 , 138 , 139 ( n , γ ) cross sections constr

Author

B. V. Kheswa, M. Wiedeking, J. A. Brown, A. C. Larsen, S. Goriely, M. Guttormsen, F. L. Bello Garrote, L. A. Bernstein, D. L. Bleuel, T. K. Eriksen, F. Giacoppo, A. Görgen, B. L. Goldblum, T. W. Hagen, P. E. Koehler, M. Klintefjord, K. L. Malatji, J. E. Midtbø, H. T. Nyhus, P. Papka, T. Renstrøm, S. J. Rose, E. Sahin, S. Siem, and T. G. Tornyi

Published
2017
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34. Statistical properties of Pu 243 , and Pu 242 ( n , γ

Author

T. A. Laplace, F. Zeiser, M. Guttormsen, A. C. Larsen, D. L. Bleuel, L. A. Bernstein, B. L. Goldblum, S. Siem, F. L. Bello Garotte, J. A. Brown, L. Crespo Campo, T. K. Eriksen, F. Giacoppo, A. Görgen, K. Hadyńska-Klȩk, R. A. Henderson, M. Klintefjord, M. Lebois, T. Renstrøm, S. J. Rose, E. Sahin, T. G. Tornyi, G. M. Tveten, A. Voinov, M. Wiedeking, J. N. Wilson, and W. Younes

Published
2016
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35. Experimentally constrained ( p , γ ) Y 89 and (

Author

A. C. Larsen, M. Guttormsen, R. Schwengner, D. L. Bleuel, S. Goriely, S. Harissopulos, F. L. Bello Garrote, Y. Byun, T. K. Eriksen, F. Giacoppo, A. Görgen, T. W. Hagen, M. Klintefjord, T. Renstrøm, S. J. Rose, E. Sahin, S. Siem, T. G. Tornyi, G. M. Tveten, A. V. Voinov, and M. Wiedeking

Published
2016
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37. Investigation of the U 238 ( d , p ) surrogate reaction via the simu

Author

Q. Ducasse, B. Jurado, M. Aïche, P. Marini, L. Mathieu, A. Görgen, M. Guttormsen, A. C. Larsen, T. Tornyi, J. N. Wilson, G. Barreau, G. Boutoux, S. Czajkowski, F. Giacoppo, F. Gunsing, T. W. Hagen, M. Lebois, J. Lei, V. Méot, B. Morillon, A. M. Moro, T. Renstrøm, O. Roig, S. J. Rose, O. Sérot, S. Siem, I. Tsekhanovich, G. M. Tveten, and M. Wiedeking

Published
2016
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38. Improving discrimination between clouds and optically thick aerosol plumes in geostationary satellite data

Author

D. Robbins, C. Poulsen, S. Siems, and S. Proud

Subjects
Environmental engineering, TA170-171, Earthwork. Foundations, TA715-787
Abstract

Cloud masking is a key initial step in the retrieval of geophysical properties from satellite data. Despite decades of research, problems still exist of over- or underdetection of clouds. High aerosol loadings, in particular from dust storms or fires, are often classified as clouds, and vice versa. In this paper, we present a cloud mask created using machine learning for the Advanced Himawari Imager (AHI) aboard Himawari-8. In order to train the algorithm, a parallax-corrected collocated data set was created from AHI and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar data. Artificial neural networks (ANNs) were trained on the collocated data to identify clouds in AHI scenes. The resulting neural network (NN) cloud masks are validated and compared to cloud masks produced by the Japanese Meteorological Association (JMA) and the Bureau of Meteorology (BoM) for a number of different solar and viewing geometries, surface types and air masses. Here, five case studies covering a range of challenging scenarios for cloud masks are also presented to demonstrate the performance of the masking algorithm. The NN mask shows a lower false positive rate (FPR) for an equivalent true positive rate (TPR) across all categories, with FPRs of 0.160 and 0.259 for the NN and JMA masks, respectively, and 0.363 and 0.506 for the NN and BoM masks, respectively, at equivalent TPR values. This indicates the NN mask accurately identifies 1.13 and 1.29 times as many non-cloud pixels for the equivalent hit rate when compared to the JMA and BoM masks, respectively. The NN mask was shown to be particularly effective in distinguishing thick aerosol plumes from cloud, most likely due to the inclusion of the 0.47 and 0.51 µm bands. The NN cloud mask shows an improvement over current operational cloud masks in most scenarios, and it is suggested that improvements to current operational cloud masks could be made by including the 0.47 and 0.51 µm bands. The collocated data are made available to facilitate future research.

Published
2022
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40. Lifetime measurments of excited states in neutron-rich fission fragments

Author

T.W. Hagen, L. Grente, A. Görgen, M.-D. Salsac, W. Korten, F. Farget, T. Braunroth, B. Bruyneel, I. Celikovic, E. Clément, G. de France, O. Delaune, A. Dewald, A. Dijon, M. Hackstein, B. Jacquot, J. Litzinger, J. Ljungvall, C. Louchart, C. Michelagnoli, D.R. Napoli, A. Navin, F. Recchia, M. Rejmund, W. Rother, E. Sahin, S. Siem, B. Sulignano, Ch. Theisen, J.J. Valiente-Dobon, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), CSNSM SNO, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), and Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)-Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM)

Subjects
Physics, Spectrometer, 010308 nuclear & particles physics, Fission, Gamma ray, General Physics and Astronomy, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Nuclear physics, symbols.namesake, Physics and Astronomy (all), Recoil, Excited state, 0103 physical sciences, symbols, Neutron, Atomic number, Atomic physics, Nuclear Experiment, Doppler effect
Abstract

Expérience GANIL/VAMOS/EXOGAM; International audience; Lifetimes of short-lived excited states in a wide range of neutron-richfission fragments were measured using the recoil distance Doppler shift(RDDS) technique, which was applied to fusion-fission reactions in inversekinematics for the first time. The fission fragments were identified eventby-event in mass, charge, and atomic number using the VAMOS magneticspectrometer at GANIL. Gamma rays originating from the fission fragmentswere measured with the EXOGAM array of Ge Clover detectors aroundthe target position. Using a degrader, the change in the Doppler shiftof the $\gamma$ ray allows the application of the RDDS method. Details of theexperimental technique will be discussed and the status for the ongoinganalysis for odd-mass yttrium isotopes will be presented.

Published
2015

41. Shell evolution beyondN=40:Cu69,71,73

Author

E. Sahin, M. Doncel, K. Sieja, G. de Angelis, A. Gadea, B. Quintana, A. Görgen, V. Modamio, D. Mengoni, J. J. Valiente-Dobón, P. R. John, M. Albers, D. Bazzacco, G. Benzoni, B. Birkenbach, B. Cederwall, E. Clément, D. Curien, L. Corradi, P. Désesquelles, A. Dewald, F. Didierjean, G. Duchêne, J. Eberth, M. N. Erduran, E. Farnea, E. Fioretto, G. de France, C. Fransen, R. Gernhäuser, A. Gottardo, M. Hackstein, T. Hagen, A. Hernández-Prieto, H. Hess, T. Hüyük, A. Jungclaus, S. Klupp, W. Korten, A. Kusoglu, S. M. Lenzi, J. Ljungvall, C. Louchart, S. Lunardi, R. Menegazzo, C. Michelagnoli, T. Mijatović, B. Million, P. Molini, G. Montagnoli, D. Montanari, O. Möller, D. R. Napoli, A. Obertelli, R. Orlandi, G. Pollarolo, A. Pullia, F. Recchia, P. Reiter, D. Rosso, W. Rother, M.-D. Salsac, F. Scarlassara, M. Schlarb, S. Siem, Pushpendra P. Singh, P.-A. Söderström, A. M. Stefanini, O. Stézowski, B. Sulignano, S. Szilner, Ch. Theisen, C. A. Ur, and M. Yalcinkaya

Subjects
Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, 0103 physical sciences, Shell (structure), 010306 general physics, 01 natural sciences, Molecular physics
Published
2015

42. Spectroscopy and single-particle structure of the odd- Z heavy elements 255Lr, 251Md and 247Es

Author

A. Chatillon, Ch. Theisen, P. T. Greenlees, G. Auger, J. E. Bastin, E. Bouchez, B. Bouriquet, J. M. Casandjian, R. Cee, E. Clément, R. Dayras, G. de France, R. de Toureil, S. Eeckhaudt, A. Görgen, T. Grahn, S. Grévy, K. Hauschild, R. -D. Herzberg, P. J. C. Ikin, G. D. Jones, P. Jones, R. Julin, S. Juutinen, H. Kettunen, A. Korichi, W. Korten, Y. Le Coz, M. Leino, A. Lopez-Martens, S. M. Lukyanov, Yu. E. Penionzhkevich, J. Perkowski, A. Pritchard, P. Rahkila, M. Rejmund, J. Saren, C. Scholey, S. Siem, M. G. Saint-Laurent, C. Simenel, Yu. G. Sobolev, Ch. Stodel, J. Uusitalo, A. Villari, M. Bender, P. Bonche, P. -H. Heenen, Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), and Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)

Subjects
Physics, Nuclear and High Energy Physics, Spin states, 010308 nuclear & particles physics, Nuclear Theory, Hadron, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, Electron spectroscopy, Cold fusion, Particle decay, Atomic orbital, Pairing, 0103 physical sciences, Atomic physics, Nuclear Experiment, 010306 general physics, Spectroscopy
Abstract

Submitted to European Physical Journal A - Expérience GANIL; The odd-Z isotope 255Lr, its daughter 251Md and grand-daughter 247Es were studied in two experiments performed at GANIL and the University of Jyväskylä. The 255Lr nuclei were produced using the cold fusion-evaporation reaction 209Bi(48Ca, 2n)255Lr at a bombarding energy of 217MeV. The single-particle structure and decay properties were investigated using α, γ and electron spectroscopy. The ground-state spin and parity could be assigned for 255Lr (1/2-) and 251Md (7/2-). States corresponding to the 7/2+[633], 7/2-[514] and 1/2-[521] Nilsson orbitals were observed. Results are compared to experimental data obtained in neighbouring isotopes and to Hartree-Fock-Bogoliubov calculations using the Skyrme interaction SLy4 and a density-dependent pairing interaction. The position of the 1/2-[521] orbital from the spherical 2f5/2 shell is discussed.

Published
2006

43. Shape Coexistence in the Neutron-Deficient Even-EvenHg182−188Isotopes Studied via Coulomb Excitation

Author

N. Bree, K. Wrzosek-Lipska, A. Petts, A. Andreyev, B. Bastin, M. Bender, A. Blazhev, B. Bruyneel, P. A. Butler, J. Butterworth, M. P. Carpenter, J. Cederkäll, E. Clément, T. E. Cocolios, A. Deacon, J. Diriken, A. Ekström, C. Fitzpatrick, L. M. Fraile, Ch. Fransen, S. J. Freeman, L. P. Gaffney, J. E. García-Ramos, K. Geibel, R. Gernhäuser, T. Grahn, M. Guttormsen, B. Hadinia, K. Hadyńska-Kle¸k, M. Hass, P.-H. Heenen, R.-D. Herzberg, H. Hess, K. Heyde, M. Huyse, O. Ivanov, D. G. Jenkins, R. Julin, N. Kesteloot, Th. Kröll, R. Krücken, A. C. Larsen, R. Lutter, P. Marley, P. J. Napiorkowski, R. Orlandi, R. D. Page, J. Pakarinen, N. Patronis, P. J. Peura, E. Piselli, P. Rahkila, E. Rapisarda, P. Reiter, A. P. Robinson, M. Scheck, S. Siem, K. Singh Chakkal, J. F. Smith, J. Srebrny, I. Stefanescu, G. M. Tveten, P. Van Duppen, J. Van de Walle, D. Voulot, N. Warr, F. Wenander, A. Wiens, J. L. Wood, and M. Zielińska

Subjects
Physics, Mean field theory, Excited state, Quadrupole, General Physics and Astronomy, Neutron, Coulomb excitation, Atomic physics, Nucleon, Ground state, 7. Clean energy, Excitation
Abstract

Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0(+) states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0(+) state was noted in Hg-182; 184. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established.

Published
2014

44. Isospin character of low-lying pygmy dipole states in 208Pb via inelastic scattering of 17O ions

Author

F C L, Crespi, A, Bracco, R, Nicolini, D, Mengoni, L, Pellegri, E G, Lanza, S, Leoni, A, Maj, M, Kmiecik, R, Avigo, G, Benzoni, N, Blasi, C, Boiano, S, Bottoni, S, Brambilla, F, Camera, S, Ceruti, A, Giaz, B, Million, A I, Morales, V, Vandone, O, Wieland, P, Bednarczyk, M, Ciemała, J, Grebosz, M, Krzysiek, K, Mazurek, M, Zieblinski, D, Bazzacco, M, Bellato, B, Birkenbach, D, Bortolato, E, Calore, B, Cederwall, L, Charles, G, de Angelis, P, Désesquelles, J, Eberth, E, Farnea, A, Gadea, A, Görgen, A, Gottardo, R, Isocrate, J, Jolie, A, Jungclaus, N, Karkour, W, Korten, R, Menegazzo, C, Michelagnoli, P, Molini, D R, Napoli, A, Pullia, F, Recchia, P, Reiter, D, Rosso, E, Sahin, M D, Salsac, B, Siebeck, S, Siem, J, Simpson, P-A, Söderström, O, Stezowski, Ch, Theisen, C, Ur, and J J, Valiente-Dobón

Abstract

The properties of pygmy dipole states in 208Pb were investigated using the 208Pb(17O, 17O'γ) reaction at 340 MeV and measuring the γ decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted γ rays and of the scattered particles were measured. The results are compared with (γ, γ') and (p, p') data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2+ and 3- states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first time. This has allowed us to extract the isoscalar component of the 1- excited states from 4 to 8 MeV.

Published
2014

46. Study of 169Hf at high rotational frequency

Author

M. Bergström, S. W. Ødegård, A. Maj, A. Bracco, L. L. Riedinger, R. Terry, H. Hübel, W. C. Ma, S. Frattini, B. Herskind, K. A. Schmidt, C. J. Lister, T. Lauritsen, J. Domscheit, P. G. Varmette, M. P. Carpenter, G. Sletten, S. Siem, Benedicte Million, T. L. Khoo, R. V. F. Janssens, G.B. Hagemann, I. Wiedenhöver, and D. J. Hartley

Subjects
Physics, Nuclear and High Energy Physics, Excited state, Quasiparticle, Degrees of freedom (physics and chemistry), Nuclear fusion, Atomic physics, Nucleon, Excitation, Spectral line, Spin-½
Abstract

High-spin properties of the nucleus 169Hf have been studied through the fusion evaporation reaction 96Zr(76Ge,3n)169Hf at a beam energy of 310 MeV. The known rotational bands have been extended considerably and 6 new bands have been established, four of which form coupled bands with pronounced M1 connections. Quasiparticle assignments are suggested for the new band structures, and it appears that coupling to vibrational degrees of freedom plays a role. Both coupled bands involve the excitation of quasiprotons. In the region of highest spin, a large alignment gain is interpreted in terms of a mixed crossing where an h 9/2 and an h 11/2 quasiproton provide the two signatures of the aligning configuration.

Published
2001

47. First evidence for triaxial superdeformation in 168Hf

Author

A. Bracco, G. Sletten, H. Amro, H. Hübel, T. Lauritsen, P.G. Varmette, I. Wiedenhöver, R. B. Piercey, S. Siem, S. Frattini, K. A. Schmidt, C. J. Lister, W. C. Ma, D. J. Hartley, J. N. Wilson, M. P. Carpenter, L. L. Riedinger, M. Bergström, B. Herskind, J. Domscheit, F. G. Kondev, Benedicte Million, T. L. Khoo, S. W. Ødegård, J. A. Winger, Gro Hagemann, and R. V. F. Janssens

Subjects
Superdeformation, Physics, Maxima and minima, Nuclear and High Energy Physics, Proton, Deformation (mechanics), Quadrupole, Atomic physics
Abstract

Three superdeformed (SD) bands have been found in 168Hf. Lifetime measurements revealed a large quadrupole moment, Q t ∼11.4 e b , for the strongest band (TSD1). Theoretical calculations using the Ultimate Cranker code predict high-spin SD minima (ϵ2∼0.43) with stable triaxial deformations of γ∼+20° and γ∼−15°. The measured Qt value suggests that band TSD1 corresponds, most likely, to a deformation with a positive γ value. This constitutes the first evidence for triaxial superdeformation in an even proton system.

Published
2001

48. Entry distribution of 220Th: A method to determine the fission barrier of an unstable nucleus

Author

F. G. Kondev, A. M. Heinz, R. V. F. Janssens, Jolie Cizewski, D. Seweryniak, C. J. Lister, W. F. Henning, P. Reiter, T. Lauritsen, I. Ahmad, M. P. Carpenter, T. L. Khoo, A. A. Sonzogni, P. Bhattacharyya, I. Wiedenhöver, C. N. Davids, G. D. Jones, Juha Uusitalo, S. Siem, R. Julin, and J. Caggiano

Subjects
Nuclear physics, Physics, Nuclear and High Energy Physics, medicine.anatomical_structure, Distribution (number theory), Fission, medicine, Atomic physics, Nucleus
Published
2001

49. Entry Distribution, Fission Barrier, and Formation Mechanism ofN102254o

Author

P. Reiter, T. L. Khoo, T. Lauritsen, C. J. Lister, D. Seweryniak, A. A. Sonzogni, I. Ahmad, N. Amzal, P. Bhattacharyya, P. A. Butler, M. P. Carpenter, A. J. Chewter, J. A. Cizewski, C. N. Davids, K. Y. Ding, N. Fotiades, J. P. Greene, P. T. Greenlees, A. Heinz, W. F. Henning, R.-D. Herzberg, R. V. F. Janssens, G. D. Jones, F. G. Kondev, W. Korten, M. Leino, S. Siem, J. Uusitalo, K. Vetter, and I. Wiedenhöver

Subjects
Physics, Angular momentum, Fission, Yrast, Nuclear Theory, Dirac (software), General Physics and Astronomy, Neutron, Atomic physics, Nuclear Experiment, Spin (physics), Energy (signal processing), Excitation
Abstract

The entry distribution in angular momentum and excitation energy for the formation of {sup 254}No has been measured after the {sup 208}Pb( {sup 48}Ca, 2 n) reaction at 215 and 219 MeV. This nucleus is populated up to spin 22({Dirac_h}/2{pi}) and excitation energy (greater-or-similar sign)6 MeV above the yrast line, with the half-maximum points of the energy distributions at {approx}5 MeV for spins between 12({Dirac_h}/2{pi}) and 22({Dirac_h}/2{pi}) . This suggests that the fission barrier is (greater-or-similar sign)5 MeV and that the shell-correction energy persists to high spin. (c) 2000 The American Physical Society.

Published
2000

50. Octupole Correlations in the Pu Isotopes: From Vibration to Static Deformation?

Author

D. Cline, John P. Greene, E. H. Seabury, A. O. Macchiavelli, J. Uusitalo, M. P. Carpenter, I. Wiedenhöver, P. Reiter, T. Lauritsen, C. J. Lister, R. V. F. Janssens, S. Siem, P. Chowdhury, P. Bhattacharyya, C. Y. Wu, G. Hackman, D. Seweryniak, Jolie Cizewski, I. Ahmad, A. A. Sonzogni, D. T. Nisius, H. Amro, and T. L. Khoo

Subjects
Physics, Vibration, Isotope, Spins, Yrast, General Physics and Astronomy, Parity (physics), Gammasphere, Atomic physics, Plutonium isotopes
Abstract

In a series of measurements with Gammasphere, striking differences were found between the yrast and negative parity bands in ${}^{238--240}\mathrm{Pu}$ and those in ${}^{241--244}\mathrm{Pu}$. These differences can be linked to variations with mass of the strength of octupole correlations. At the highest spins, ${}^{238--240}\mathrm{Pu}$ are found to exhibit properties associated with stable octupole deformation, suggesting that a transition with spin from a vibration to stable deformation may have occurred.

Published
1999

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