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Start Over Author "Stefanescu, I." Publisher amer physical soc
16 results on '"Stefanescu, I."'

1. Spectroscopic Quadrupole Moments in Sr-96,Sr-98: Evidence for Shape Coexistence in Neutron-Rich Strontium Isotopes at N=60

Author

Clement, E., Zielinska, M., Gorgen, A., Korten, W., Peru, S., Libert, J., Goutte, H., Hilaire, S., Bastin, B., Bauer, C., Blazhev, A., Bree, N., Bruyneel, B., Butler, P. A., Butterworth, J., Delahaye, P., Dijon, A., Doherty, D. T., Ekstrom, A., Fitzpatrick, C., Fransen, C., Georgiev, G., Gernhaeuser, R., Hess, H., Iwanicki, J., Jenkins, D. G., Larsen, A. C., Ljungvall, J., Lutter, R., Marley, P., Moschner, K., Napiorkowski, P. J., Pakarinen, J., Petts, A., Reiter, P., Renstrom, T., Seidlitz, M., Siebeck, B., Siem, S., Sotty, C., Srebrny, J., Stefanescu, I., Tveten, G. M., Van de Walle, J., Vermeulen, M., Voulot, D., Warr, N., Wenander, F., Wiens, A., De Witte, H., Wrzosek-Lipska, K., Clement, E., Zielinska, M., Gorgen, A., Korten, W., Peru, S., Libert, J., Goutte, H., Hilaire, S., Bastin, B., Bauer, C., Blazhev, A., Bree, N., Bruyneel, B., Butler, P. A., Butterworth, J., Delahaye, P., Dijon, A., Doherty, D. T., Ekstrom, A., Fitzpatrick, C., Fransen, C., Georgiev, G., Gernhaeuser, R., Hess, H., Iwanicki, J., Jenkins, D. G., Larsen, A. C., Ljungvall, J., Lutter, R., Marley, P., Moschner, K., Napiorkowski, P. J., Pakarinen, J., Petts, A., Reiter, P., Renstrom, T., Seidlitz, M., Siebeck, B., Siem, S., Sotty, C., Srebrny, J., Stefanescu, I., Tveten, G. M., Van de Walle, J., Vermeulen, M., Voulot, D., Warr, N., Wenander, F., Wiens, A., De Witte, H., and Wrzosek-Lipska, K.

Abstract

Neutron-rich Sr-96,Sr-98 isotopes have been investigated by safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility. Reduced transition probabilities and spectroscopic quadrupole moments have been extracted from the differential Coulomb excitation cross sections. These results allow, for the first time, the drawing of definite conclusions about the shape coexistence of highly deformed prolate and spherical configurations. In particular, a very small mixing between the coexisting states is observed, contrary to other mass regions where strong mixing is present. Experimental results have been compared to beyond-mean-field calculations using the Gogny D1S interaction in a five-dimensional collective Hamiltonian formalism, which reproduce the shape change at N = 60.

Published
2016

2. Low-energy Coulomb excitation of Sr-96,Sr-98 beams

Author

Clement, E., Zielinska, M., Peru, S., Goutte, H., Hilaire, S., Gorgen, A., Korten, W., Doherty, D. T., Bastin, B., Bauer, C., Blazhev, A., Bree, N., Bruyneel, B., Butler, P. A., Butterworth, J., Cederkall, J., Delahaye, P., Dijon, A., Ekstrom, A., Fitzpatrick, C., Fransen, C., Georgiev, G., Gernhauser, R., Hess, H., Iwanicki, J., Jenkins, D. G., Larsen, A. C., Ljungvall, J., Lutter, R., Marley, P., Moschner, K., Napiorkowski, P. J., Pakarinen, J., Petts, A., Reiter, P., Renstrom, T., Seidlitz, M., Siebeck, B., Siem, S., Sotty, C., Srebrny, J., Stefanescu, I., Tveten, G. M., Van de Walle, J., Vermeulen, M., Voulot, D., Warr, N., Wenander, F., Wiens, A., De Witte, H., Wrzosek-Lipska, K., Clement, E., Zielinska, M., Peru, S., Goutte, H., Hilaire, S., Gorgen, A., Korten, W., Doherty, D. T., Bastin, B., Bauer, C., Blazhev, A., Bree, N., Bruyneel, B., Butler, P. A., Butterworth, J., Cederkall, J., Delahaye, P., Dijon, A., Ekstrom, A., Fitzpatrick, C., Fransen, C., Georgiev, G., Gernhauser, R., Hess, H., Iwanicki, J., Jenkins, D. G., Larsen, A. C., Ljungvall, J., Lutter, R., Marley, P., Moschner, K., Napiorkowski, P. J., Pakarinen, J., Petts, A., Reiter, P., Renstrom, T., Seidlitz, M., Siebeck, B., Siem, S., Sotty, C., Srebrny, J., Stefanescu, I., Tveten, G. M., Van de Walle, J., Vermeulen, M., Voulot, D., Warr, N., Wenander, F., Wiens, A., De Witte, H., and Wrzosek-Lipska, K.

Abstract

The structure of neutron-rich Sr-96,Sr-98 nuclei was investigated by low-energy safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. A rich set of transitional and diagonal E2 matrix elements, including those for non-yrast structures, has been extracted from the differential Coulomb-excitation cross sections. The results support the scenario of a shape transition at N = 60, giving rise to the coexistence of a highly deformed prolate and a spherical configuration in Sr-98, and are compared to predictions from several theoretical calculations. The experimental data suggest a significant contribution of the triaxal degree of freedom in the ground state of both isotopes. In addition, experimental information on low-lying states in Rb-98 has been obtained.

Published
2016

3. Spectroscopic Quadrupole Moments in Sr-96,Sr-98: Evidence for Shape Coexistence in Neutron-Rich Strontium Isotopes at N=60

Author

Clement, E., Zielinska, M., Gorgen, A., Korten, W., Peru, S., Libert, J., Goutte, H., Hilaire, S., Bastin, B., Bauer, C., Blazhev, A., Bree, N., Bruyneel, B., Butler, P. A., Butterworth, J., Delahaye, P., Dijon, A., Doherty, D. T., Ekstrom, A., Fitzpatrick, C., Fransen, C., Georgiev, G., Gernhaeuser, R., Hess, H., Iwanicki, J., Jenkins, D. G., Larsen, A. C., Ljungvall, J., Lutter, R., Marley, P., Moschner, K., Napiorkowski, P. J., Pakarinen, J., Petts, A., Reiter, P., Renstrom, T., Seidlitz, M., Siebeck, B., Siem, S., Sotty, C., Srebrny, J., Stefanescu, I., Tveten, G. M., Van de Walle, J., Vermeulen, M., Voulot, D., Warr, N., Wenander, F., Wiens, A., De Witte, H., Wrzosek-Lipska, K., Clement, E., Zielinska, M., Gorgen, A., Korten, W., Peru, S., Libert, J., Goutte, H., Hilaire, S., Bastin, B., Bauer, C., Blazhev, A., Bree, N., Bruyneel, B., Butler, P. A., Butterworth, J., Delahaye, P., Dijon, A., Doherty, D. T., Ekstrom, A., Fitzpatrick, C., Fransen, C., Georgiev, G., Gernhaeuser, R., Hess, H., Iwanicki, J., Jenkins, D. G., Larsen, A. C., Ljungvall, J., Lutter, R., Marley, P., Moschner, K., Napiorkowski, P. J., Pakarinen, J., Petts, A., Reiter, P., Renstrom, T., Seidlitz, M., Siebeck, B., Siem, S., Sotty, C., Srebrny, J., Stefanescu, I., Tveten, G. M., Van de Walle, J., Vermeulen, M., Voulot, D., Warr, N., Wenander, F., Wiens, A., De Witte, H., and Wrzosek-Lipska, K.

Abstract

Neutron-rich Sr-96,Sr-98 isotopes have been investigated by safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility. Reduced transition probabilities and spectroscopic quadrupole moments have been extracted from the differential Coulomb excitation cross sections. These results allow, for the first time, the drawing of definite conclusions about the shape coexistence of highly deformed prolate and spherical configurations. In particular, a very small mixing between the coexisting states is observed, contrary to other mass regions where strong mixing is present. Experimental results have been compared to beyond-mean-field calculations using the Gogny D1S interaction in a five-dimensional collective Hamiltonian formalism, which reproduce the shape change at N = 60.

Published
2016

4. Low-energy Coulomb excitation of Sr-96,Sr-98 beams

Author

Clement, E., Zielinska, M., Peru, S., Goutte, H., Hilaire, S., Gorgen, A., Korten, W., Doherty, D. T., Bastin, B., Bauer, C., Blazhev, A., Bree, N., Bruyneel, B., Butler, P. A., Butterworth, J., Cederkall, J., Delahaye, P., Dijon, A., Ekstrom, A., Fitzpatrick, C., Fransen, C., Georgiev, G., Gernhauser, R., Hess, H., Iwanicki, J., Jenkins, D. G., Larsen, A. C., Ljungvall, J., Lutter, R., Marley, P., Moschner, K., Napiorkowski, P. J., Pakarinen, J., Petts, A., Reiter, P., Renstrom, T., Seidlitz, M., Siebeck, B., Siem, S., Sotty, C., Srebrny, J., Stefanescu, I., Tveten, G. M., Van de Walle, J., Vermeulen, M., Voulot, D., Warr, N., Wenander, F., Wiens, A., De Witte, H., Wrzosek-Lipska, K., Clement, E., Zielinska, M., Peru, S., Goutte, H., Hilaire, S., Gorgen, A., Korten, W., Doherty, D. T., Bastin, B., Bauer, C., Blazhev, A., Bree, N., Bruyneel, B., Butler, P. A., Butterworth, J., Cederkall, J., Delahaye, P., Dijon, A., Ekstrom, A., Fitzpatrick, C., Fransen, C., Georgiev, G., Gernhauser, R., Hess, H., Iwanicki, J., Jenkins, D. G., Larsen, A. C., Ljungvall, J., Lutter, R., Marley, P., Moschner, K., Napiorkowski, P. J., Pakarinen, J., Petts, A., Reiter, P., Renstrom, T., Seidlitz, M., Siebeck, B., Siem, S., Sotty, C., Srebrny, J., Stefanescu, I., Tveten, G. M., Van de Walle, J., Vermeulen, M., Voulot, D., Warr, N., Wenander, F., Wiens, A., De Witte, H., and Wrzosek-Lipska, K.

Abstract

The structure of neutron-rich Sr-96,Sr-98 nuclei was investigated by low-energy safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. A rich set of transitional and diagonal E2 matrix elements, including those for non-yrast structures, has been extracted from the differential Coulomb-excitation cross sections. The results support the scenario of a shape transition at N = 60, giving rise to the coexistence of a highly deformed prolate and a spherical configuration in Sr-98, and are compared to predictions from several theoretical calculations. The experimental data suggest a significant contribution of the triaxal degree of freedom in the ground state of both isotopes. In addition, experimental information on low-lying states in Rb-98 has been obtained.

Published
2016

5. Coulomb excitation of neutron-rich Cd isotopes

Author

Ilieva, S., Thuerauf, M., Kroell, Th., Kruecken, R., Behrens, T., Bildstein, V., Blazhev, A., Boenig, S., Butler, P. A., Cederkaell, J., Davinson, T., Delahaye, P., Diriken, J., Ekstroem, A., Finke, F., Fraile, L. M., Franchoo, S., Fransen, Ch., Georgiev, G., Gernhaeuser, R., Habs, D., Hess, H., Hurst, A. M., Huyse, M., Ivanov, O., Iwanicki, J., Kent, P., Kester, O., Koester, U., Lutter, R., Mahgoub, M., Martin, D., Mayet, P., Maierbeck, P., Morgan, T., Niedermeier, O., Pantea, M., Reiter, P., Rodriguez, T. R., Rolke, Th., Scheit, H., Scherillo, A., Schwalm, D., Seidlitz, M., Sieber, T., Simpson, G. S., Stefanescu, I., Thiel, S., Thirolf, P. G., Van de Walle, J., Van Duppen, P., Voulot, D., Warr, N., Weinzierl, W., Weisshaar, D., Wenander, F., Wiens, A., Winkler, S., Ilieva, S., Thuerauf, M., Kroell, Th., Kruecken, R., Behrens, T., Bildstein, V., Blazhev, A., Boenig, S., Butler, P. A., Cederkaell, J., Davinson, T., Delahaye, P., Diriken, J., Ekstroem, A., Finke, F., Fraile, L. M., Franchoo, S., Fransen, Ch., Georgiev, G., Gernhaeuser, R., Habs, D., Hess, H., Hurst, A. M., Huyse, M., Ivanov, O., Iwanicki, J., Kent, P., Kester, O., Koester, U., Lutter, R., Mahgoub, M., Martin, D., Mayet, P., Maierbeck, P., Morgan, T., Niedermeier, O., Pantea, M., Reiter, P., Rodriguez, T. R., Rolke, Th., Scheit, H., Scherillo, A., Schwalm, D., Seidlitz, M., Sieber, T., Simpson, G. S., Stefanescu, I., Thiel, S., Thirolf, P. G., Van de Walle, J., Van Duppen, P., Voulot, D., Warr, N., Weinzierl, W., Weisshaar, D., Wenander, F., Wiens, A., and Winkler, S.

Abstract

The isotopes (122),(124),Cd-126 were studied in a safe Coulomb-excitation experiment at the radioactive ion-beam facility REX-ISOLDE at CERN. The reduced transition probabilities B(E2; 0(g. s)(vertical bar) -> 2(1)(+)) and limits for the quadrupole moments of the first 2(+) excited states in the three isotopes were determined. The onset of collectivity in the vicinity of the Z = 50 and N = 82 shell closures is discussed by comparison with shell model and beyond mean-field calculations.

Published
2014

6. Shape Coexistence in the Neutron- Deficient Even-Even Hg182-188 Isotopes Studied via Coulomb Excitation

Author

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

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

7. Coulomb excitation of neutron-rich Cd isotopes

Author

Ilieva, S., Thuerauf, M., Kroell, Th., Kruecken, R., Behrens, T., Bildstein, V., Blazhev, A., Boenig, S., Butler, P. A., Cederkaell, J., Davinson, T., Delahaye, P., Diriken, J., Ekstroem, A., Finke, F., Fraile, L. M., Franchoo, S., Fransen, Ch., Georgiev, G., Gernhaeuser, R., Habs, D., Hess, H., Hurst, A. M., Huyse, M., Ivanov, O., Iwanicki, J., Kent, P., Kester, O., Koester, U., Lutter, R., Mahgoub, M., Martin, D., Mayet, P., Maierbeck, P., Morgan, T., Niedermeier, O., Pantea, M., Reiter, P., Rodriguez, T. R., Rolke, Th., Scheit, H., Scherillo, A., Schwalm, D., Seidlitz, M., Sieber, T., Simpson, G. S., Stefanescu, I., Thiel, S., Thirolf, P. G., Van de Walle, J., Van Duppen, P., Voulot, D., Warr, N., Weinzierl, W., Weisshaar, D., Wenander, F., Wiens, A., Winkler, S., Ilieva, S., Thuerauf, M., Kroell, Th., Kruecken, R., Behrens, T., Bildstein, V., Blazhev, A., Boenig, S., Butler, P. A., Cederkaell, J., Davinson, T., Delahaye, P., Diriken, J., Ekstroem, A., Finke, F., Fraile, L. M., Franchoo, S., Fransen, Ch., Georgiev, G., Gernhaeuser, R., Habs, D., Hess, H., Hurst, A. M., Huyse, M., Ivanov, O., Iwanicki, J., Kent, P., Kester, O., Koester, U., Lutter, R., Mahgoub, M., Martin, D., Mayet, P., Maierbeck, P., Morgan, T., Niedermeier, O., Pantea, M., Reiter, P., Rodriguez, T. R., Rolke, Th., Scheit, H., Scherillo, A., Schwalm, D., Seidlitz, M., Sieber, T., Simpson, G. S., Stefanescu, I., Thiel, S., Thirolf, P. G., Van de Walle, J., Van Duppen, P., Voulot, D., Warr, N., Weinzierl, W., Weisshaar, D., Wenander, F., Wiens, A., and Winkler, S.

Abstract

The isotopes (122),(124),Cd-126 were studied in a safe Coulomb-excitation experiment at the radioactive ion-beam facility REX-ISOLDE at CERN. The reduced transition probabilities B(E2; 0(g. s)(vertical bar) -> 2(1)(+)) and limits for the quadrupole moments of the first 2(+) excited states in the three isotopes were determined. The onset of collectivity in the vicinity of the Z = 50 and N = 82 shell closures is discussed by comparison with shell model and beyond mean-field calculations.

Published
2014

8. Shape Coexistence in the Neutron- Deficient Even-Even Hg182-188 Isotopes Studied via Coulomb Excitation

Author

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

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

9. Spectroscopy of excited states in U-234 and search for a two-phonon state in U-234

Author

Kotthaus, T., Reiter, P., Bruyneel, B., Chatzistamatiou, M., Eberth, J., Gersch, G., Hess, H., Stefanescu, I., Warr, N., Weisshaar, D., Wiens, A., Morgan, T., Lutter, R., Schwerdtfeger, W., Thirolf, P. G., Bringel, P., Huebel, H., Neusser-Neffgen, A., Kotthaus, T., Reiter, P., Bruyneel, B., Chatzistamatiou, M., Eberth, J., Gersch, G., Hess, H., Stefanescu, I., Warr, N., Weisshaar, D., Wiens, A., Morgan, T., Lutter, R., Schwerdtfeger, W., Thirolf, P. G., Bringel, P., Huebel, H., and Neusser-Neffgen, A.

Abstract

Excited states of the isotope U-234 were studied employing the one-neutron transfer reaction U-235(d, t)U-234 at a beam energy of 11 MeV. The reaction channel was selected by an identification of the outgoing tritons in a Delta E-E measurement. In coincidence with the tritons, gamma rays were also detected with the highly efficient MINIBALL spectrometer. Based on the analysis of gamma gamma coincidence data, the level scheme of U-234 was extended. The 4(+) state at an energy of 1886.7 keV provides evidence for a possible two-phonon gamma gamma excitation, which is based on three gamma transitions from this state to the gamma vibrational band. However, this state is populated with a high cross section via the one-neutron transfer reaction, which is not expected for a highly collective excitation. The situation is compared to other known cases from the rare-earth region and to the neighboring isotone Th-232, which so far is the only known case for a two-phonon excitation in the actinide region.

Published
2013

10. Spectroscopy of excited states in U-234 and search for a two-phonon state in U-234

Author

Kotthaus, T., Reiter, P., Bruyneel, B., Chatzistamatiou, M., Eberth, J., Gersch, G., Hess, H., Stefanescu, I., Warr, N., Weisshaar, D., Wiens, A., Morgan, T., Lutter, R., Schwerdtfeger, W., Thirolf, P. G., Bringel, P., Huebel, H., Neusser-Neffgen, A., Kotthaus, T., Reiter, P., Bruyneel, B., Chatzistamatiou, M., Eberth, J., Gersch, G., Hess, H., Stefanescu, I., Warr, N., Weisshaar, D., Wiens, A., Morgan, T., Lutter, R., Schwerdtfeger, W., Thirolf, P. G., Bringel, P., Huebel, H., and Neusser-Neffgen, A.

Abstract

Excited states of the isotope U-234 were studied employing the one-neutron transfer reaction U-235(d, t)U-234 at a beam energy of 11 MeV. The reaction channel was selected by an identification of the outgoing tritons in a Delta E-E measurement. In coincidence with the tritons, gamma rays were also detected with the highly efficient MINIBALL spectrometer. Based on the analysis of gamma gamma coincidence data, the level scheme of U-234 was extended. The 4(+) state at an energy of 1886.7 keV provides evidence for a possible two-phonon gamma gamma excitation, which is based on three gamma transitions from this state to the gamma vibrational band. However, this state is populated with a high cross section via the one-neutron transfer reaction, which is not expected for a highly collective excitation. The situation is compared to other known cases from the rare-earth region and to the neighboring isotone Th-232, which so far is the only known case for a two-phonon excitation in the actinide region.

Published
2013

11. Prolate shape of Ba-140 from a first combined Doppler-shift and Coulomb-excitation measurement at the REX-ISOLDE facility

Author

Bauer, C., Behrens, T., Bildstein, V., Blazhev, A., Bruyneel, B., Butterworth, J., Clement, E., Coquard, L., Egido, J. L., Ekstrom, A., Fitzpatrick, C. R., Fransen, C., Gernhaeuser, R., Habs, D., Hess, H., Leske, J., Kroell, T., Kruecken, R., Lutter, R., Marley, P., Moeller, T., Otsuka, T., Patronis, N., Petts, A., Pietralla, N., Rodriguez, T. R., Shimizu, N., Stahl, C., Stefanescu, I., Stora, T., Thirolf, P. G., Voulot, D., de Walle, J. Van, Warr, N., Wenander, F., Wiens, A., Bauer, C., Behrens, T., Bildstein, V., Blazhev, A., Bruyneel, B., Butterworth, J., Clement, E., Coquard, L., Egido, J. L., Ekstrom, A., Fitzpatrick, C. R., Fransen, C., Gernhaeuser, R., Habs, D., Hess, H., Leske, J., Kroell, T., Kruecken, R., Lutter, R., Marley, P., Moeller, T., Otsuka, T., Patronis, N., Petts, A., Pietralla, N., Rodriguez, T. R., Shimizu, N., Stahl, C., Stefanescu, I., Stora, T., Thirolf, P. G., Voulot, D., de Walle, J. Van, Warr, N., Wenander, F., and Wiens, A.

Abstract

Background: Quadrupole moments of excited nuclear states are important observables for geometrically interpreting nuclear structure in terms of deformed shapes, although data are scarce and sometimes ambiguous, in particular, in neutron-rich nuclides. Purpose: A measurement was performed for determining the spectroscopic quadrupole moment of the 2(1)(+) state of Ba-140 in order to clarify the character of quadrupole deformation (prolate or oblate) of the state in its yrast sequence of levels. Method: We have utilized a new combined technique of lifetime measurement at REX-ISOLDE and MINIBALL using the Doppler-shift attenuation method (DSAM) and a reorientation analysis of Coulomb-excitation yields. Results: On the basis of the new lifetime of tau(2(1)(+)) = 10.4(-0.8)(+2.2) ps the electric quadrupole moment was determined to be Q(2(1)(+)) = -0.52(34) eb, indicating a predominant prolate deformation. Conclusions: This finding is in agreement with beyond-mean-field calculations using the Gogny D1S force and with results from the Monte Carlo shell-model approach.

Published
2012

12. Prolate shape of Ba-140 from a first combined Doppler-shift and Coulomb-excitation measurement at the REX-ISOLDE facility

Author

Bauer, C., Behrens, T., Bildstein, V., Blazhev, A., Bruyneel, B., Butterworth, J., Clement, E., Coquard, L., Egido, J. L., Ekstrom, A., Fitzpatrick, C. R., Fransen, C., Gernhaeuser, R., Habs, D., Hess, H., Leske, J., Kroell, T., Kruecken, R., Lutter, R., Marley, P., Moeller, T., Otsuka, T., Patronis, N., Petts, A., Pietralla, N., Rodriguez, T. R., Shimizu, N., Stahl, C., Stefanescu, I., Stora, T., Thirolf, P. G., Voulot, D., de Walle, J. Van, Warr, N., Wenander, F., Wiens, A., Bauer, C., Behrens, T., Bildstein, V., Blazhev, A., Bruyneel, B., Butterworth, J., Clement, E., Coquard, L., Egido, J. L., Ekstrom, A., Fitzpatrick, C. R., Fransen, C., Gernhaeuser, R., Habs, D., Hess, H., Leske, J., Kroell, T., Kruecken, R., Lutter, R., Marley, P., Moeller, T., Otsuka, T., Patronis, N., Petts, A., Pietralla, N., Rodriguez, T. R., Shimizu, N., Stahl, C., Stefanescu, I., Stora, T., Thirolf, P. G., Voulot, D., de Walle, J. Van, Warr, N., Wenander, F., and Wiens, A.

Abstract

Background: Quadrupole moments of excited nuclear states are important observables for geometrically interpreting nuclear structure in terms of deformed shapes, although data are scarce and sometimes ambiguous, in particular, in neutron-rich nuclides. Purpose: A measurement was performed for determining the spectroscopic quadrupole moment of the 2(1)(+) state of Ba-140 in order to clarify the character of quadrupole deformation (prolate or oblate) of the state in its yrast sequence of levels. Method: We have utilized a new combined technique of lifetime measurement at REX-ISOLDE and MINIBALL using the Doppler-shift attenuation method (DSAM) and a reorientation analysis of Coulomb-excitation yields. Results: On the basis of the new lifetime of tau(2(1)(+)) = 10.4(-0.8)(+2.2) ps the electric quadrupole moment was determined to be Q(2(1)(+)) = -0.52(34) eb, indicating a predominant prolate deformation. Conclusions: This finding is in agreement with beyond-mean-field calculations using the Gogny D1S force and with results from the Monte Carlo shell-model approach.

Published
2012

13. Coulomb excitation of the 3(-) isomer in Cu-70

Author

Rapisarda, E., Stefanescu, I., Balabanski, D. L., Bastin, B., Blazhev, A., Bree, N., Danchev, M., Bruyneel, B., Davinson, T., Delahaye, P., Diriken, J., Eberth, J., Georgiev, G., Fedorov, D., Fedosseev, V. N., Fiori, E., Franchoo, S., Fransen, Ch, Geibel, K., Gladnishki, K., Hadynska, K., Hess, H., Heyde, K., Huyse, M., Ivanov, O., Iwanicki, J., Jolie, J., Kalkuehler, M., Kroell, Th, Kruecken, R., Koester, U., Lo Bianco, G., Lozeva, R., Marsh, B. A., Nardelli, S., Nowacki, F., Patronis, N., Reiter, P., Seidlitz, M., Sieja, K., Smirnova, N., Srebrny, J., Van de Walle, J., Van Duppen, P., Warr, N., Wenander, F., Wimmer, K., Wrzosek, K., Zemlyanoi, S., Zielinska, M., Rapisarda, E., Stefanescu, I., Balabanski, D. L., Bastin, B., Blazhev, A., Bree, N., Danchev, M., Bruyneel, B., Davinson, T., Delahaye, P., Diriken, J., Eberth, J., Georgiev, G., Fedorov, D., Fedosseev, V. N., Fiori, E., Franchoo, S., Fransen, Ch, Geibel, K., Gladnishki, K., Hadynska, K., Hess, H., Heyde, K., Huyse, M., Ivanov, O., Iwanicki, J., Jolie, J., Kalkuehler, M., Kroell, Th, Kruecken, R., Koester, U., Lo Bianco, G., Lozeva, R., Marsh, B. A., Nardelli, S., Nowacki, F., Patronis, N., Reiter, P., Seidlitz, M., Sieja, K., Smirnova, N., Srebrny, J., Van de Walle, J., Van Duppen, P., Warr, N., Wenander, F., Wimmer, K., Wrzosek, K., Zemlyanoi, S., and Zielinska, M.

Abstract

Post-accelerated isomerically purified radioactive beams, available at the CERN On-Line Isotope Mass Separator facility using the resonant ionization laser technique, have been used to study the Coulomb excitation of the I-pi = 3(-) state in Cu-70 (Z = 29, N = 41). While first results using a I-pi = 6(-) beam were reported previously, the present complementary experiment allows us to complete the study of the multiplet of states (3(-), 4(-), 5(-), 6(-)) arising from the pi 2p(3)/(2)nu 1g(9/2) configuration. Besides the known gamma-ray transition deexciting the 4(-) state, a ground-state. ray of 511(3) keV was observed for the first time and was unambiguously associated with the 5(-) state deexcitation. This observation fixes the energy, spin, and parity of this state, completing the low-energy level scheme of Cu-70. B(E2) values for all possible E2 transitions within the multiplet were determined. A comparison with large-scale shell model calculations using different interactions and valence spaces shows the importance of proton excitation across the Z = 28 shell gap and the role of the 2d(5/2) neutron orbital.

Published
2011

14. Coulomb excitation of the 3(-) isomer in Cu-70

Author

Rapisarda, E., Stefanescu, I., Balabanski, D. L., Bastin, B., Blazhev, A., Bree, N., Danchev, M., Bruyneel, B., Davinson, T., Delahaye, P., Diriken, J., Eberth, J., Georgiev, G., Fedorov, D., Fedosseev, V. N., Fiori, E., Franchoo, S., Fransen, Ch, Geibel, K., Gladnishki, K., Hadynska, K., Hess, H., Heyde, K., Huyse, M., Ivanov, O., Iwanicki, J., Jolie, J., Kalkuehler, M., Kroell, Th, Kruecken, R., Koester, U., Lo Bianco, G., Lozeva, R., Marsh, B. A., Nardelli, S., Nowacki, F., Patronis, N., Reiter, P., Seidlitz, M., Sieja, K., Smirnova, N., Srebrny, J., Van de Walle, J., Van Duppen, P., Warr, N., Wenander, F., Wimmer, K., Wrzosek, K., Zemlyanoi, S., Zielinska, M., Rapisarda, E., Stefanescu, I., Balabanski, D. L., Bastin, B., Blazhev, A., Bree, N., Danchev, M., Bruyneel, B., Davinson, T., Delahaye, P., Diriken, J., Eberth, J., Georgiev, G., Fedorov, D., Fedosseev, V. N., Fiori, E., Franchoo, S., Fransen, Ch, Geibel, K., Gladnishki, K., Hadynska, K., Hess, H., Heyde, K., Huyse, M., Ivanov, O., Iwanicki, J., Jolie, J., Kalkuehler, M., Kroell, Th, Kruecken, R., Koester, U., Lo Bianco, G., Lozeva, R., Marsh, B. A., Nardelli, S., Nowacki, F., Patronis, N., Reiter, P., Seidlitz, M., Sieja, K., Smirnova, N., Srebrny, J., Van de Walle, J., Van Duppen, P., Warr, N., Wenander, F., Wimmer, K., Wrzosek, K., Zemlyanoi, S., and Zielinska, M.

Abstract

Post-accelerated isomerically purified radioactive beams, available at the CERN On-Line Isotope Mass Separator facility using the resonant ionization laser technique, have been used to study the Coulomb excitation of the I-pi = 3(-) state in Cu-70 (Z = 29, N = 41). While first results using a I-pi = 6(-) beam were reported previously, the present complementary experiment allows us to complete the study of the multiplet of states (3(-), 4(-), 5(-), 6(-)) arising from the pi 2p(3)/(2)nu 1g(9/2) configuration. Besides the known gamma-ray transition deexciting the 4(-) state, a ground-state. ray of 511(3) keV was observed for the first time and was unambiguously associated with the 5(-) state deexcitation. This observation fixes the energy, spin, and parity of this state, completing the low-energy level scheme of Cu-70. B(E2) values for all possible E2 transitions within the multiplet were determined. A comparison with large-scale shell model calculations using different interactions and valence spaces shows the importance of proton excitation across the Z = 28 shell gap and the role of the 2d(5/2) neutron orbital.

Published
2011

15. Coulomb excitation of Ga-73

Author

Diriken, J., Stefanescu, I., Balabanski, D., Blasi, N., Blazhev, A., Bree, N., Cederkaell, J., Cocolios, T. E., Davinson, T., Eberth, J., Ekstrom, A., Fedorov, D. V., Fedosseev, V. N., Fraile, L. M., Franchoo, S., Georgiev, G., Gladnishki, K., Huyse, M., Ivanov, O. V., Ivanov, V. S., Iwanicki, J., Jolie, J., Konstantinopoulos, T., Kroell, Th., Kruecken, R., Koester, U., Lagoyannis, A., Lo Bianco, G., Maierbeck, P., Marsh, B. A., Napiorkowski, P., Patronis, N., Pauwels, D., Reiter, P., Seliverstov, M., Sletten, G., Van de Walle, J., Van Duppen, P., Voulot, D., Walters, W. B., Warr, N., Wenander, F., Wrzosek, K., Diriken, J., Stefanescu, I., Balabanski, D., Blasi, N., Blazhev, A., Bree, N., Cederkaell, J., Cocolios, T. E., Davinson, T., Eberth, J., Ekstrom, A., Fedorov, D. V., Fedosseev, V. N., Fraile, L. M., Franchoo, S., Georgiev, G., Gladnishki, K., Huyse, M., Ivanov, O. V., Ivanov, V. S., Iwanicki, J., Jolie, J., Konstantinopoulos, T., Kroell, Th., Kruecken, R., Koester, U., Lagoyannis, A., Lo Bianco, G., Maierbeck, P., Marsh, B. A., Napiorkowski, P., Patronis, N., Pauwels, D., Reiter, P., Seliverstov, M., Sletten, G., Van de Walle, J., Van Duppen, P., Voulot, D., Walters, W. B., Warr, N., Wenander, F., and Wrzosek, K.

Abstract

The B(E2; I-i -> I-f) values for transitions in Ga-71(31)40 and Ga-73(31)42 were deduced from a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using post-accelerated beams of Ga-71,Ga-73 at the REX-ISOLDE on-line isotope mass separator facility. The emitted gamma rays were detected by the MINIBALL gamma-detector array, and B(E2; I-i -> I-f) values were obtained from the yields normalized to the known strength of the 2(+) -> 0(+) transition in the Sn-120 target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the E2 collectivity toward lower excitation energy when adding neutrons beyond N = 40. This supports conclusions from previous studies of the gallium isotopes, which indicated a structural change in this isotopic chain between N = 40 and 42. Combined with recent measurements from collinear laser spectroscopy showing a 1/2(-) spin and parity for the ground state, the extracted results revealed evidence for a 1/2(-), 3/2(-) doublet near the ground state in Ga-73(31)42 differing by at most 0.8 keV in energy.

Published
2010

16. Coulomb excitation of Ga-73

Author

Diriken, J., Stefanescu, I., Balabanski, D., Blasi, N., Blazhev, A., Bree, N., Cederkaell, J., Cocolios, T. E., Davinson, T., Eberth, J., Ekstrom, A., Fedorov, D. V., Fedosseev, V. N., Fraile, L. M., Franchoo, S., Georgiev, G., Gladnishki, K., Huyse, M., Ivanov, O. V., Ivanov, V. S., Iwanicki, J., Jolie, J., Konstantinopoulos, T., Kroell, Th., Kruecken, R., Koester, U., Lagoyannis, A., Lo Bianco, G., Maierbeck, P., Marsh, B. A., Napiorkowski, P., Patronis, N., Pauwels, D., Reiter, P., Seliverstov, M., Sletten, G., Van de Walle, J., Van Duppen, P., Voulot, D., Walters, W. B., Warr, N., Wenander, F., Wrzosek, K., Diriken, J., Stefanescu, I., Balabanski, D., Blasi, N., Blazhev, A., Bree, N., Cederkaell, J., Cocolios, T. E., Davinson, T., Eberth, J., Ekstrom, A., Fedorov, D. V., Fedosseev, V. N., Fraile, L. M., Franchoo, S., Georgiev, G., Gladnishki, K., Huyse, M., Ivanov, O. V., Ivanov, V. S., Iwanicki, J., Jolie, J., Konstantinopoulos, T., Kroell, Th., Kruecken, R., Koester, U., Lagoyannis, A., Lo Bianco, G., Maierbeck, P., Marsh, B. A., Napiorkowski, P., Patronis, N., Pauwels, D., Reiter, P., Seliverstov, M., Sletten, G., Van de Walle, J., Van Duppen, P., Voulot, D., Walters, W. B., Warr, N., Wenander, F., and Wrzosek, K.

Abstract

The B(E2; I-i -> I-f) values for transitions in Ga-71(31)40 and Ga-73(31)42 were deduced from a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using post-accelerated beams of Ga-71,Ga-73 at the REX-ISOLDE on-line isotope mass separator facility. The emitted gamma rays were detected by the MINIBALL gamma-detector array, and B(E2; I-i -> I-f) values were obtained from the yields normalized to the known strength of the 2(+) -> 0(+) transition in the Sn-120 target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the E2 collectivity toward lower excitation energy when adding neutrons beyond N = 40. This supports conclusions from previous studies of the gallium isotopes, which indicated a structural change in this isotopic chain between N = 40 and 42. Combined with recent measurements from collinear laser spectroscopy showing a 1/2(-) spin and parity for the ground state, the extracted results revealed evidence for a 1/2(-), 3/2(-) doublet near the ground state in Ga-73(31)42 differing by at most 0.8 keV in energy.

Published
2010

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