Investigations into the alpha-decay ofH. 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. Uusitalo1
1 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
(Received: 16 September 2002 / Revised version: 4 December 2002 / Published online: 25 March 2003)
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 T1/2=328(20) ms. Another state with an alpha-decay energy keV and a half-life T1/2=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.
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