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

A.N. Andreyev; K. Van de Vel; A. Barzakh; A. De Smet; H. De Witte; D.V. Fedorov; V.N. Fedoseyev; S. Franchoo; M. Górska; M. Huyse; Z. Janas; U. Köster; W. Kurcewicz; J. Kurpeta; V.I. Mishin; K. Partes; A. Plochocki; P. Van Duppen; L. Weissman

doi:doi:10.1140/epja/iepja1387

2022 Impact factor 2.7

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. Franchoo^{5, 6}, M. Górska², M. Huyse^{2, 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, T_1/2=4.3(2) s, respectively; while for the $I^{\pi}=3/2^-$ isomer ( T_1/2=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