Fine structure in the $\ensuremath{\alpha}$ decay of $^{188,192}\mathrm{Po}$

Fine structure in the $α$ decay of ${}^{188, 192}{Po}$

K. Van de Vel, A. N. Andreyev, D. Ackermann, H. J. Boardman, P. Cagarda, J. Gerl, F. P. Heßberger, S. Hofmann, M. Huyse, D. Karlgren, I. Kojouharov, M. Leino, B. Lommel, G. Münzenberg, C. Moore, R. D. Page, S. Saro, P. Van Duppen, and R. Wyss

Phys. Rev. C 68, 054311 – Published 21 November 2003

Abstract

The $α$ decay of ${}^{188, 192}{Po}$ has been reexamined in order to probe the $0^{+}$ states in the daughter nuclei ${}^{184, 188}{Pb}$ that can be associated with coexisting spherical, oblate, and∕or prolate configurations. Improved values were measured for the excitation energy and the feeding $α$ -decay intensity of the $0_{2}^{+}$ state in ${}^{184, 188}{Pb}$ and conflicting results on the $0_{3}^{+}$ state in ${}^{188}{Pb}$ were clarified. All known cases of fine structure in the $α$ decay of the even-even Po nuclei are reviewed. The reduced $α$ -decay width systematics combined with potential-energy-surface calculations confirm the onset of deformation in the ground state of the polonium nuclei around the neutron midshell. An isomeric state with a half-life of $580 (100) ns$ has been identified in ${}^{192}{Po}$ .

Received 3 July 2003

DOI:https://doi.org/10.1103/PhysRevC.68.054311

Authors & Affiliations

K. Van de Vel¹, A. N. Andreyev^2,*, D. Ackermann^3,4, H. J. Boardman², P. Cagarda³, J. Gerl³, F. P. Heßberger³, S. Hofmann³, M. Huyse¹, D. Karlgren^1,5, I. Kojouharov³, M. Leino⁶, B. Lommel³, G. Münzenberg³, C. Moore², R. D. Page², S. Saro³, P. Van Duppen¹, and R. Wyss⁵

¹Instituut voor Kern- en Stralingsfysica, University of Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
²Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE, United Kingdom
³Gesellschaft für Schwerionenforschung, Planckstrasse 1, 64291 Darmstadt, Germany
⁴Johannes Gutenberg-Universität, 55099 Mainz, Germany
⁵Department of Physics, Royal Institute of Technology, 104 05 Stockholm, Sweden
⁶Department of Physics, University of Jyväskylä, 40014 Jyväskylä, Finland

^*Corresponding author. Email address: aan@ns.ph.liv.ac.uk

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Vol. 68, Iss. 5 — November 2003

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Figure 1
(a) Single $α$ -particle energy spectrum collected in the ${}^{52}{Cr} + {}^{142}{Nd}$ reaction between the beam pulses. The prominent peaks are assigned to known activities and for some specific lines the $α$ -particle energies are given in keV. (b) Energy spectrum of $α$ decays correlated with a recoil within $90 ms$ . (c) The same spectrum as in (b), but in prompt coincidence with a low-energy signal registered in the electron detector. The inset shows the spectrum expanded for the energy range $6250 keV - 6550 keV$ .Reuse & Permissions
Figure 2
Energy spectrum of $γ$ -rays deexciting an isomer. The $γ$ rays were measured by the focal plane Clover detector in coincidence with recoils tagged with the $α$ decay of ${}^{192}{Po}$ . Energies are given in keV, the transitions labeled with stars have been observed previously via in-beam $γ$ -ray spectroscopy studies reported in Refs. 24, 26. The inset shows the ground-state band for ${}^{192}{Po}$ from Refs. 24, 26.Reuse & Permissions
Figure 3
(a) Energy spectrum of $α$ decays correlated with a recoil within $1.2 ms$ using the ${}^{52}{Cr} + {}^{142}{Nd}$ and ${}^{50}{Cr} + {}^{142}{Nd}$ reactions. The prominent peaks are assigned to known activities and for some specific lines the $α$ -particle energies are given in keV. (b) Mother and daughter $α$ -particle energies for all chains of the type recoil- $α_{1} − α_{2}$ . Maximum correlation times were $1.2 ms$ for the recoil- $α_{1}$ pair and $2.5 s$ for the $α_{1} − α_{2}$ pair. (c) The same as in (b), but in prompt coincidence with a signal registered in the electron detector.Reuse & Permissions
Figure 4
Potential energy surfaces calculated for ${}^{188, 190, 192}{Po}$ and ${}^{184, 186, 188}{Pb}$ . Spherical, oblate, and prolate minima are indicated with circles, squares, and triangles, respectively. The energy separation between the contour lines is $50 keV$ . The axis of oblate deformation is indicated with $γ = - 60 °$ and of prolate deformation with $γ = 0 °$ .Reuse & Permissions
Figure 5
Reduced $α$ -decay widths as a function of parent neutron number for the decay of Po to the different $0^{+}$ states in the Pb isotopes. The ground-state to ground-state decay of Po is shown with filled circles. The reduced widths for the decay to the presumed oblate and prolate $0^{+}$ states are shown with squares and triangles, respectively. The sum of the values for the different fine-structure $α$ decays is shown with stars. The reduced $α$ -width values for the $α$ decay of Rn are shown with crosses. Lines connect similar configurations to guide the eye. Experimental results are taken from Refs. 5, 7, 12, 31, 39 and the present work.Reuse & Permissions

Physical Review C

covering nuclear physics

Fine structure in the $α$ decay of ${}^{188, 192}{Po}$

K. Van de Vel, A. N. Andreyev, D. Ackermann, H. J. Boardman, P. Cagarda, J. Gerl, F. P. Heßberger, S. Hofmann, M. Huyse, D. Karlgren, I. Kojouharov, M. Leino, B. Lommel, G. Münzenberg, C. Moore, R. D. Page, S. Saro, P. Van Duppen, and R. Wyss

Phys. Rev. C 68, 054311 – Published 21 November 2003

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Physical Review C

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Fine structure in the α decay of Po188,192

K. Van de Vel, A. N. Andreyev, D. Ackermann, H. J. Boardman, P. Cagarda, J. Gerl, F. P. Heßberger, S. Hofmann, M. Huyse, D. Karlgren, I. Kojouharov, M. Leino, B. Lommel, G. Münzenberg, C. Moore, R. D. Page, S. Saro, P. Van Duppen, and R. Wyss

Phys. Rev. C 68, 054311 – Published 21 November 2003

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Fine structure in the $α$ decay of ${}^{188, 192}{Po}$