2018 Impact factor 2.481
Hadrons and Nuclei


Eur. Phys. J. A 14, 63-75 (2002)
DOI: 10.1140/epja/iepja1387

Nuclear spins, magnetic moments and $\mth{\alpha}$-decay spectroscopy of long-lived isomeric states in $\chem{{^{185}Pb}}$

A.N. Andreyev1, K. Van de Vel2, A. Barzakh3, A. De Smet2, H. De Witte2, D.V. Fedorov3, V.N. Fedoseyev4, S. Franchoo5, 6, M. Górska2, M. Huyse2, 5, Z. Janas7, U. Köster5, W. Kurcewicz7, J. Kurpeta7, V.I. Mishin4, K. Partes5, A. Plochocki7, P. Van Duppen2 and L. Weissman5

1  Department of Physics, Oliver Lodge Laboratory, University of Liverpool, PO Box 147, Liverpool, L69 7ZE, United Kingdom
2  Instituut voor Kern- en Stralingsfysica, University of Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
3  Petersburg Nuclear Physics Institute, 188300, Gatchina, Russia
4  Institute of Spectroscopy, Russian Academy of Sciences, 142190, Troitsk, Russia
5  ISOLDE CERN, CH-1211 Genève 23, Switzerland
6  University of Mainz, D-55099, Mainz, Germany
7  Institute of Experimental Physics, University of Warsaw, Hoza 69, PL-00681, Warsaw, Poland IS387 Collaboration and ISOLDE Collaboration

aan@ns.ph.liv.ac.uk

(Received: 7 February 2002 / Revised version: 18 February 2002 Communicated by J. Äystö)

Abstract
Alpha-decay properties of the neutron-deficient isotope 185Pb were studied at the PSB-ISOLDE (CERN) on-line mass separator using the resonance ionisation laser ion source (RILIS). The nuclei of interest were produced in a 1.4 GeV proton-induced spallation reaction of a uranium graphite target. In contrast to previous studies, two $\alpha$-decaying isomeric states were identified in 185Pb. The relative production of the isomers, monitored by their $\alpha$-counting rates, could be significantly changed when a narrow-bandwidth laser at the RILIS setup was used to scan through the atomic hyperfine structure. Based on the atomic hyperfine structure measurements, along with the systematics for heavier odd-mass lead isotopes, the spin and the parity of these states were interpreted as 3/2 - and 13/2 + and their nuclear magnetic moments were deduced. The $\alpha$-decay energy and half-life value for the $I^{\pi}=13/2^+$ isomer are $E_{\alpha}=6408(5)$ keV, T1/2=4.3(2) s, respectively; while for the $I^{\pi}=3/2^-$ isomer ( T1/2=6.3(4) s) two $\alpha$-decays with $E_{\alpha1}=6288(5)$ keV, $I_{\alpha1}=56(2)\%$ and $E_{\alpha2}=6486(5)$ keV, $I_{\alpha2}=44(2)\%$ were observed. By observing prompt $\alpha$- $\gamma$ coincidences new information on the low-lying states in the daughter isotope 181Hg was obtained.

PACS
27.70.+q - $150\leq A \leq 189$ .
23.60.+e - Alpha decay.
32.10.Dk - Electric and magnetic moments, polarizability.
32.10.Fn - Fine and hyperfine structure.

© Società Italiana di Fisica, Springer-Verlag 2002