First observation of the $\mth{\nu\, 9/2[404]}$ orbital in the $\mth{A\sim 100}$ mass region

W. Urban; J.A. Pinston; T. Rząca-Urban; A. Złomaniec; G. Simpson; J.L. Durell; W.R. Phillips; A.G. Smith; B.J. Varley; I. Ahmad; N. Schulz

doi:doi:10.1140/epja/i2002-10104-y

2022 Impact factor 2.7

Hadrons and Nuclei

Eur. Phys. J. A 16, 11-15 (2003)
DOI: 10.1140/epja/i2002-10104-y

Short Note

First observation of the $\mth{\nu\, 9/2[404]}$ orbital in the $\mth{A\sim 100}$ mass region

W. Urban¹, J.A. Pinston², T. Rzaca-Urban¹, A. Zlomaniec¹, G. Simpson³, J.L. Durell⁴, W.R. Phillips⁴, A.G. Smith⁴, B.J. Varley⁴, I. Ahmad⁵ and N. Schulz⁶

¹ Institute of Experimental Physics, Warsaw University, ul. Hoza 69, 00-681 Warszawa, Poland
² Institut des Sciences Nucléaires, F-38026 Grenoble Cedex, France
³ Institut Laue-Langevin, F-38042 Grenoble Cedex, France
⁴ Schuster Laboratory, Department of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
⁵ Argonne National Laboratory, Argonne, IL 60439, USA
⁶ Institut de Recherches Subatomiques UMR7500, CNRS-IN2P3 et Université Louis Pasteur, 67037 Strasbourg, France

urban@fuw.edu.pl

(Received: 11 September 2002 / Published online: 17 January 2003)

Abstract
A new band, populated by the spontaneous fission of ²⁴⁸Cm and studied by means of prompt $\gamma$ -ray spectroscopy using the EUROGAM2 array, was observed in ⁹⁹Zr. The 1038.8 keV band head with a half-life T_1/2=54(10) ns is interpreted as a K-isomer, corresponding to the 9/2[404] neutron-hole excitation. It is the first observation of this orbital in the mass $A\sim 100$ region. The quadrupole moment, Q₀=3.9(3) eb deduced for the new band indicates a large deformation of ${\beta}_2=0.41$ , which is produced by a specific shape-coexistence mechanism, known in other regions and now found in the $A\sim 100$ nuclei.

PACS
23.20.Lv - Gamma transitions and level energies.
21.60.Cs - Shell model.
25.85.Ca - Spontaneous fission.
27.60.+j - $90 \leq A \leq 149$ .

© Società Italiana di Fisica, Springer-Verlag 2003