Low energy 0⁺ excitations in ¹⁵⁸Gd

J.G. Hirsch*, G. Popa, S.R. Lesher**, A. Aprahamian, C.E. Vargas*** and J.P. Draayer****

* Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70–543 México 04510 DF, México

** Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA
Currently at K.U. Leuven, Instituut voor Kern– en Stralingsfysica, Celestijnenlaan 200D, B–3001 Leuven, Belgium.

*** Facultad de Física e Inteligencia Artificial, Universidad Veracruzana, Sebastián Camacho 5, Xalapa, Ver. 91000, México

****Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, U.S.A

Recibido el 9 de febrero de 2005
Aceptado el 29 de marzo de 2005

Abstract

High precision (p,t) studies of the deformed nucleus ¹⁵⁸Gd allowed the observation of 13 excited 0⁺ states below an excitation energy of 3.1 MeV. This high density of low energy states, and particularly their measured B (E2) transition strengths to the first excited 2⁺ state challenge nuclear models. The pseudo SU (3) model, which successfully describes many excited bands in Dy isotopes, is used to analyze this nuclei. We have fairly good reproduction of most of the states but the absence of actively including nucleons occupying intruders orbits may be the reason for the observed limitations of the model.

Keywords: Algebraic models; nuclear structure; deformed nuclei.

Resumen

Estudios de alta precisión (p,t) del núcleo deformado 158Gd han permitido la observación de 13 estados excitados 0+ a una energía abajo de 3.1 MeV. Esta alta densidad de estados de baja energía y particularmente la medida de sus transiciones B (E2) al primer estado 2+ representa un desafío para cualquier modelo nuclear. Se utiliza el modelo pseudo SU (3), que describe adecuadamente un gran número de bandas excitadas en los isótopos de Dy, para estudiar el 158Gd. Encontramos que el modelo describe adecuadamente la mayoria de los estados, sin embargo, es posible que el hecho de excluir a los nucleones ocupando estados de paridad intrusa sea la principal limitante del modelo.

Descriptores: Modelos algebraicos; estructura nuclear; nucleos deformados.

PACS: 21.60.Fw;23.20.Js;27.70.+q

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Acknowledgments

This work was supported in part by Conacyt (Mexico), DGAPA–UNAM, and the U.S. National Science Foundation, including the contract PHY01–40324.

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