Eur. Phys. J. A 16, 457-467 (2003)
DOI: 10.1140/epja/i2002-10130-9

Investigations into the alpha-decay of

H. Kettunen¹, T. Enqvist¹, M. Leino¹, K. Eskola², P.T. Greenlees¹, K. Helariutta¹, P. Jones¹, R. Julin¹, S. Juutinen¹, H. Kankaanpää¹, H. Koivisto¹, P. Kuusiniemi¹, M. Muikku¹, P. Nieminen¹, P. Rahkila¹ and J. Uusitalo<sup>1

1</sup>  Department of Physics, University of Jyväskylä, P.O. Box 35, FIN-40014 Jyväskylä, Finland
²  Department of Physical Sciences, University of Helsinki, FIN-00014 Helsinki, Finland

heikki.kettunen@phys.jyu.fi

(Received: 16 September 2002 / Revised version: 4 December 2002 / Published online: 25 March 2003)

Abstract
The low-energy nuclear structure and decay properties of the neutron-deficient isotopes ¹⁹⁵At and ¹⁹¹Bi have been studied. ¹⁹⁵At was produced in the reaction ¹⁴²Nd( ⁵⁶Fe,p2n) ¹⁹⁵At and ¹⁹¹Bi as the daughter activity of ¹⁹⁵At. The activities were implanted in a position-sensitive silicon detector after being separated from the primary beam by a gas-filled recoil separator. The 1/2 ⁺ intruder state was determined to be the ground state in ¹⁹⁵At with an alpha-decay energy of  keV and a half-life T_1/2=328(20) ms. Another state with an alpha-decay energy  keV and a half-life T_1/2=147(5) ms was found to decay to a 148.7(5) keV excited state in ¹⁹¹Bi for which a spin and parity of 7/2 ^- were deduced. Consequently, the same 7/2 ^- character was assigned to the initial state at 32(7) keV in ¹⁹⁵At on the basis of unhindered alpha-decay. The 9/2 ^- state, being the ground state in heavier odd-mass astatine isotopes, was not observed.

PACS
23.60.+e - Alpha decay.
27.80.+w - .
23.20.Lv - Gamma transitions and level energies.
21.10.Dr - Binding energies and masses.

© Società Italiana di Fisica, Springer-Verlag 2003