Eur. Phys. J. A 11, 257-261 (2001)

Isomeric state of ⁸⁰Y and its role in the astrophysical rp-process

Yu.N. Novikov^{1, 2}, H. Schatz³, P. Dendooven⁴, R. Béraud⁵, Ch. Miehé⁶, A.V. Popov¹, D.M. Seliverstov¹, G.K. Vorobjev², P. Baumann⁶, M.J.G. Borge⁷, G. Canchel⁵, Ph. Desagne⁶, A. Emsallem⁵, W. Huang⁴, J. Huikari⁴, A. Jokinen⁴, A. Knipper⁶, V. Kolhinen⁴, A. Nieminen⁴, M. Oinonen⁸, H. Penttilä⁴, K. Peräjärvi⁴, I. Piqueras^{6, 7}, S. Rinta-Antila⁴, J. Szerypo⁴, Y. Wang⁴ and J. Äystö<sup>8

1</sup>  St. Petersburg Nuclear Physics Institute, Gatchina, 188350, Russia
²  St. Petersburg State University, St. Petersburg, 198904, Russia
³  Michigan State University, East Lansing, MI 48824, USA
⁴  Department of Physics, University of Jyväskylä, Jyväskylä, 40351, Finland
⁵  Institut de Physique Nucléaire de Lyon, CNRS-IN2P3 and Université Claude Bernard, 69622 Villeurbanne Cedex, France
⁶  Institut de Recherches Subatomiques, UMR7500, CNRS-IN2P3 and Université Louis Pasteur, BP28, 67037 Strasbourg Cedex, France
⁷  Instituto de Estructura de la Materia, 28006 Madrid, Spain
⁸  ISOLDE, CERN, CH-1211, Geneva 23, Switzerland

novikov@pnpi.spb.ru

(Received: 14 March 2001 / Revised version: 3 July 2001 Communicated by C. Signorini)

Abstract
A careful investigation of the isomeric transition of the long-lived state at 228.5 keV excitation energy in ⁸⁰Y has been done. The HIGISOL facility at the Jyväskylä isochronous cyclotron has been used. We used the electron magnetic transporter to prepare an appropriate source and to measure the electron spectra in clean background conditions. The measured internal conversion coefficient allows unambiguous 1^- identification for the 228.5 keV first excited isomeric state in ⁸⁰Y. With a "bare" half-life of s found in this work, this state is strongly populated in the rp-process during X-ray bursts and has therefore to be taken into account in X-ray burst model calculations. However, because of the similarity of the -decay half-lives of isomeric and ground states, we find a maximum reduction in the effective -decay lifetime of ⁸⁰Y of only % . Our results pave the way for a future investigation of the impact of the isomeric state on the "effective" ⁸⁰Y proton capture rate.

PACS
21.10.Tg - Lifetimes.
23.20.Nx - Internal conversion and extranuclear effects.
27.50.+e - .

© Società Italiana di Fisica, Springer-Verlag 2001