F. Flavigny,1,2 J. Elseviers,2 A. N. Andreyev,3,4 C. Bauer,5 V. Bildstein,6 A. Blazhev,7 B. A. Brown,8 H. De Witte,2 J. Diriken,2,9 V. N. Fedosseev,10 S. Franchoo,1 R. Gernhäuser,11 M. Huyse,2 S. Ilieva,5 S. Klupp,11 Th. Kröll,5 R. Lutter,11 B. A. Marsh,10 D. Mücher,6,11 K. Nowak,11 T. Otsuka,12,13,14,2 J. Pakarinen,15,16,17 N. Patronis,18 R. Raabe,2 F. Recchia,19 P. Reiter,7 T. Roger,20 S. Sambi,2 M. Seidlitz,7 M. D. Seliverstov,2,10,21 B. Siebeck,7 Y. Tsunoda,14 P. Van Duppen,2 M. Vermeulen,3 M. Von Schmid,5 D. Voulot,10 N. Warr,7 F. Wenander,10 and K. Wimmer8,* 1Institut de Physique Nucléaire, CNRS-IN2P3, Université Paris-Sud, Université Paris-Saclay, 91406 Orsay, France 2KU Leuven, Instituut voor Kernen Stralingsfysica, 3001 Leuven, Belgium 3Department of Physics, University of York, York, YO10 5DD, United Kingdom 4Advanced Science Research Center (ASRC), Japan Atomic Energy Agency (JAEA), Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan 5Institut für Kernphysik, Technische Universität Darmstadt, Germany 6Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1, Canada 7IKP, University of Cologne, D-50937 Cologne, Germany 8Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory,

The isotope 176 Au has been studied in the complete fusion reaction 40 Ca + 141 Pr → 176 Au + 5 n at the velocity filter SHIP (GSI, Darmstadt). The complex fine-structure α decay of two isomeric states in 176 Au feeding several previously unknown excited states in the daughter nucleus 172 Ir is presented. An α -decay branching ratio of b α = 9.5(11)% was deduced for the high-spin isomer in 172 Ir.

A detailed $\\ensuremath{\\alpha}$-decay study of the neutron-deficient isotope $^{181}\\mathrm{Pb}$ has been performed in the complete fusion reaction $^{40}\\mathrm{Ca}$$+$$^{144}\\mathrm{Sm}$$\\ensuremath{\\rightarrow}$$^{184}\\mathrm{Pb}$${}^{*}$ at the velocity filter SHIP (GSI, Darmstadt). In comparison with the literature, more precise data have been deduced for the ${I}^{\\ensuremath{\\pi}}=(9/{2}^{\\ensuremath{-}})$ ground state in this nucleus, which is presumably based on the neutron $\\ensuremath{\\nu}{h}_{9/2}$ spherical orbital. Improved $\\ensuremath{\\alpha}$-decay data were also measured for $^{180}\\mathrm{Pb}$.

The reduced transition probabilities, $B(E2;{0}_{\mathrm{gs}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})$, have been measured in the radioactive isotopes $^{108,106}\mathrm{Sn}$ using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation $\ensuremath{\gamma}$ rays were detected by the highly segmented MINIBALL Ge-detector array. The results, $B(E2;{0}_{\mathrm{gs}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})=0.222(19){e}^{2}{b}^{2}$ for $^{108}\mathrm{Sn}$ and $B(E2;{0}_{\mathrm{gs}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})=0.195(39){e}^{2}{b}^{2}$ for $^{106}\mathrm{Sn}$ were determined relative to a stable $^{58}\mathrm{Ni}$ target. The resulting $B(E2)$ values are $\ensuremath{\sim}30%$ larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the $N=Z=50$ shell closure.

The short-lived isomeric states in the TZ=1 nuclei, 94mPd [T1/2=0.6(1) μs] and 96mAg [T1/2=0.7(2) μs], were identified among the fragmentation products of the 112Sn (63A MeV) + natNi (93.5 mg/cm2) reaction at GANIL. The separation and identification of the reaction products was done by means of the Alpha and LISE3 magnetic spectrometers combined with time-of-flight, energy-loss, and total kinetic energy measurements. Evidence for isomeric states in 80Y, 98Cd, and 102Sn was also obtained.Received 30 October 1996DOI:https://doi.org/10.1103/PhysRevC.55.1126©1997 American Physical Society

As an application of extended TDHF method, the excitation energies of low-lying 0 + intruder states in even-even nuclei are studied. System treated in this paper is schematic one, i.e., the shell-model in which protons move in two single-particle levels and neutrons in a single-particle level. The Hamiltonian consists of the protons pairing interaction and the proton-neutron quadrupole interaction. The system is transcribed in classical mechanics and after certain approximation, requantized. The intruder states very naturally appear within an aligned coupling scheme for the neutrons. Besides a theoretical study of eigenvalues and eigenvectors describing a few proton particle-hole excitations, an application to the Pb region is given.

Levels in the $^{192}$,194,196,198,200Pb isotopes were studied via the ${\ensuremath{\beta}}^{+}$/electron-capture decay of mass separated Bi isotopes. Multiscaled spectra of \ensuremath{\gamma} rays, x rays, and conversion electrons, and \ensuremath{\gamma}-\ensuremath{\gamma} and \ensuremath{\gamma}-${\mathrm{e}}^{\mathrm{\ensuremath{-}}}$ coincidences were measured. The existence of ${0}^{+}$ states in the $^{192\mathrm{\ensuremath{-}}200}\mathrm{Pb}$ nuclei is shown and evidence for the beginning of a collective band built on top of the ${0}_{2}^{+}$ states is seen in $^{192}$,194,196Pb. A discussion in terms of characteristic properties of intruder states in the even-even nuclei and in terms of a one-broken-neutron-pair formalism is given. This shows clearly the presence of both neutron and proton [\ensuremath{\pi}(2p-2h)] based states in the semimagic Pb nuclei at low excitation energy.

Abstract The decays of neutron-deficient 15 s 99Ag and 124 s 99gAg nuclides have been investigated at the Leuven Isotope Separator on-line facility. Sources were produced by the 92Mo(14N, 2p5n) and nat Zr ( 14 N , x n ) reactions. Positron, conversion electron, X- and γ-ray singles spectra together with γ-γ coincidence measurements have been performed on mass-separated samples. The 1 2 − isomeric level in 99)Ag decays with a 163.6 keV isomeric transition to a 7 2 + level at 342.6 keV. Of the 106 γ-rays observed in the β + EC decay of the 99Ag ground state, 68 γ-rays (92 % of the γ-ray intensity) have been placed in a proposed level scheme. The relative variation of the J π = 9 2 + and 1 2 − levels in odd-mass Ag isotopes has been calculated using a residual proton-neutron delta interaction. The occurrence of decoupled bands in the odd Pd isotopes is discussed. Detailed calculations for 99Pd have been carried out in the framework of the Nilsson model (strong-coupling wave functions) using a strong Coriolis band mixing. Energy spectra for high-spin states, wave functions and low-lying non-yrast levels (below Ex = 1 MeV) are also discussed.