Adopted values for the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even–even nuclides are given in Table I. Values of τ, the mean life of the 2+ state; E, the energy; and β, the quadrupole deformation parameter, are also listed there. The ratio of β to the value expected from the single-particle model is presented. The intrinsic quadrupole moment, Q0, is deduced from the B(E2)↑ value. The product E×B(E2)↑ is expressed as a percentage of the energy-weighted total and isoscalar E2 sum-rule strengths.

Table II presents the data on which Table I is based, namely the experimental results for B(E2)↑ values with quoted uncertainties. Information is also given on the quantity measured and the method used. The literature has been covered to November 2000.

The adopted B(E2)↑ values are compared in Table III with the values given by systematics and by various theoretical models. Predictions of unmeasured B(E2)↑ values are also given in Table III.

Transition probability from the ground to the first-excited 2^+ state of even-even nuclides

Beta decay of highly charged ions has attracted much attention in recent years. An obvious motivation for this research is that stellar nucleosynthesis proceeds at high temperatures where the involved atoms are highly ionized. Another important reason is addressing decays of well-defined quantum-mechanical systems, such as one-electron ions where all interactions with other electrons are excluded. The largest modifications of nuclear half-lives with respect to neutral atoms have been observed in beta decay of highly charged ions. These studies can be performed solely at ion storage rings and ion traps, because there high atomic charge states can be preserved for extended periods of time (up to several hours). Currently, all experimental results available in this field originate from experiments at the heavy-ion complex GSI in Darmstadt. There, the fragment separator facility FRS allows the production and separation of exotic, highly charged nuclides, which can then be stored and investigated in the storage ring facility ESR. In this review, we present and discuss in particular two-body beta decays, namely bound-state beta decay and orbital electron capture. Although we focus on experiments conducted at GSI, we will also attempt to provide general requirements common to any other experiment in this context. Finally, we address challenging but not yet performed experiments and we give prospects for the new radioactive beam facilities, such as FAIR in Darmstadt, IMP in Lanzhou and RIKEN in Wako.

Beta decay of highly charged ions

In-beamγ ray spectroscopy withγ singles spectra,γγ coincidences andγ ray angular distributions has been performed with several target-projectile combinations:natCa +32S,natCa +40Ca,54Fe +14N,58Ni +12C,58Ni +14N,66Zn +16O,68Zn +16O Level schemes of66Ge,68Ge,69As,70Se,74Kr,80Sr and82Sr have been deduced The following level energies and spin-parity assignments have been found:66Ge: 9574 keV, 2+; 16937; 21747, (4+); 36857; 42075;68Ge: 10158, 2+; 17779, 2+; 22679, 4+; 24288, 3(+); 26491, 3−; 35823, (5−); 36493, (5−); 36962, (6+); 38833, (6−); 40544, (7−); 44546; 48373;69As: 982; 1646;7896;8632; 1306;2160;22104;28315;32583;32635;39911;51957;70Se: 9454, 2+; 16009; 20394, (4+);74Kr: 4557, 2+; 10135, (4+); 17815;80Sr: 3854, 2+; 9802, (4+); 17632, (6+);82Sr: 5734, 2+; 13285,(4+); 22296,(6+) 
γ ray activity spectra have been measured after the bombardment of natural Ca with32S The half-life of the new isotope69Se has been found to be 27±3 sec Recoil distance Doppler-shift measurements have been performed with the reactions62,64Ni,66zn(16O, 2n)76, 78 Kr,80Sr The following half-lives have been determined:76Kr: 4238 keV, 2+, 37±5 psec; 10342,4+, 57±16;78Kr: 4553, 2+, 25±3; 11200, 4+, 38±1;80Sr: 3854, 2+, 44±6 The energy and half-life systematics of the first excited state of even-even nuclei suggest a maximum of nuclear deformation in the region 28≦N, Z≦50 near
 38
 76
 Sr38 or
 40
 78
 Zr38

Investigation of neutron deficient nuclei in the region 28<N, Z <50 with the help of heavy ion compound reactions

We propose to install a storage ring at an ISOL-type radioactive beam facility for the first time. Specifically, we intend to setup the heavy-ion, low-energy ring TSR at the HIE-ISOLDE facility in CERN, Geneva. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning from investigations of nuclear ground-state properties and reaction studies of astrophysical relevance, to investigations with highly-charged ions and pure isomeric beams. The TSR might also be employed for removal of isobaric contaminants from stored ion beams and for systematic studies within the neutrino beam programme. In addition to experiments performed using beams recirculating within the ring, cooled beams can also be extracted and exploited by external spectrometers for high-precision measurements. The existing TSR, which is presently in operation at the Max-Planck Institute for Nuclear Physics in Heidelberg, is well-suited and can be employed for this purpose. The physics cases as well as technical details of the existing ring facility and of the beam and infrastructure requirements at HIE-ISOLDE are discussed in the present technical design report.

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Storage ring at HIE-ISOLDE Technical design report

Nuclear Data Sheets for A = 98

Neutron deficient even-even isotopes of Kr, Se, Ge and pseudo SU3 coupling

32S and12C induced compound reactions on Fe, Ni and Se targets have been used to produce neutron deficient nuclei in the mass region 84≦A ≦87. In-beamγ-ray spectroscopy consisting of the measurement of excitation functions,γγ coincidences andγ-ray angular distributions has been performed. The following level energies and spin-parity values have been deduced:84Zr: 540 keV, 2+; 1262.8, (4+); 2137.2, (6+); 3089.286Zr: 751.9, 2+; 1666.6, (4+); 2670.0, (6+); 2705.5, (5); 3271.3; 3298.5, (8+); 3423.5, (7); 3531.5, (10+); 3645.9; 4326.1; 4417.3 Half-lives and energies ofγ-rays from the residual activities have been measured. The existence of three new isotopes could be established by their radioactive decay:84Nb(12±3 s)→84Zr86Nb(80±12 s)→86Zr87Mo(14.6±1.5 s)→87Nb→87Zr

Investigation of neutron deficient Zr and Nb nuclei with heavy ion induced compound reactions

205Tl has been previously proposed as a geological detector for solar neutrinos, making use of the reaction 205Tl(ν,e−)205Pb with a neutrino threshold of only ≂43 keV. We report on an experiment performed to study the feasibility of detecting radioactive 205Pb nuclei (T1/2=15 million years) at very low concentrations using the recently developed technique of accelerator mass spectrometry. Empolying the high‐energy ion beams of good quality from the UNILAC heavy‐ion accelerator at the GSI Darmstadt, we are able to demonstrate a suppression of neighbouring isotopes to better than 1 in 1016 and of neighbouring elements to about 1 in 103. While these results are very encouraging, the minimum number of atoms detectable is still severely limited by the efficiency of producing mulitply‐charged ions from present ion sources. Future improvements in ion‐source performance are briefly discussed.

W. Kutschera

Papers

Investigation of neutron deficient nuclei in the region 28<N, Z <50 with the help of heavy ion compound reactions

Neutron deficient even-even isotopes of Kr, Se, Ge and pseudo SU3 coupling

Investigation of neutron deficient Zr and Nb nuclei with heavy ion induced compound reactions

The 205T1 experiment

Multi-nucleon transfer near the coulomb barrier induced by 32S and 34S