Eur. Phys. J. A (2004) 21: 365-368
https://doi.org/10.1140/epja/i2004-10066-0

Letter

Prolate deformation in the ^187,189Bi isotopes

¹ DAPNIA/SPhN CEA-Saclay, 91191, Gif-sur-Yvette Cedex, France
² JYFL, University of Jyväskylä, Jyväskylä, Finland
³ Department of Physics, University of Liverpool, Liverpool, UK

^* e-mail: lecoz@cea.fr

Abstract

Prompt and delayed gamma-ray spectroscopy of very neutron-deficient bismuth isotopes ^{187, 189}Bi has been performed using the recoil decay tagging method. A rotational band has been observed in ¹⁸⁹Bi and is interpreted as a complete decoupling of a single proton from the deformed lead core. The results for ¹⁸⁷Bi suggest a similar structure and coupling scheme. This study gives the first evidence for a prolate band in a light bismuth nucleus and confirms the prolate character of the low-lying rotational band observed in the core nuclei ¹⁸⁸Pb and ¹⁸⁶Pb.