O. Klepper

Alpha decay of neutron-deficient isotopes with 52 ≦ Z ≦ 55, including the new isotopes 106Te (T12 = 60 μs) and 110Xe

Abstract Using 58Ni(58Ni,.xpγn) reactions and on-line mass separation, the α-decays of very neutron-deficient isotopes of tellurium, iodine, xenon and cesium were studied. The new isotopes 106 Te (T 1 2 = 60 − + μ s ) and 110Xe were identified by their α-lines of 4160 ± 30 keV and 3737 ± 30 keV energy, respectively, with the genetic relationship between the two successive α-decays being verified experimentally, while for several other α-decaying isotopes more precise data were obtained. The observed α-decay properties are discussed within the systematics of energy and reduced width.

Decay studies of neutron-rich isotopes of manganese, iron, cobalt, nickel, copper and zinc

Abstract A 46 mg/cm2 thick natW target was irradiated with an 11.5 MeV/u 82Se beam. On-line massseparated samples of projectile-like neutron-rich products from multi-nucleon transfer reactions were investigated by βγ spectroscopy in the mass region A = 52–79. Decay properties of the nuclei 61Mn (0.71 s), 64Fe (2.0 s), 65Co (1.25 s), 69Ni (10 s) and 73mZn (5.8 s) were measured for the first time. For 67Ni a decay scheme could be constructed using information from new γ-transitions. The known decay schemes of 60Mn, 63Fe, 63Co and 69Cu were extended. New half-life values of neutron-rich isotopes are compared with theoretical predictions.

Decay studies of neutron-rich products from 76Ge induced multinucleon transfer reactions including the new isotopes 62Mn, 63Fe and 71, 72, 73Cu

Abstract By irradiating a nat W target with 9 MeV/u 76 Ge ions, neutron-rich isotopes in the chromiumgermanium region were produced. On-line mass-separated samples were investigated. The new isotopes 62 Mn, 71 Cu, 72 Cu and 73 Cu were identified and their half-lives measured to be 0.88(15), 19.5(16), 6.6(1) and 3.9(3) s, respectively. The half-life of 63 Fe, a nucleus which has previously been detected using particle-identification techniques, was measured to be 4.9(5) s. Decay schemes were derived in most cases. Additional spectroscopic information was obtained on the decays of 73 Zn and 74 Zn. We give evidence that the earlier reported γ-ray activity attributed to 67 Ni belongs to the decay of the 70 Cu isomers. At A = 67 we observed a new β-ray activity of 21(1) s half-life which is here assigned to the decay of 67 Ni.

Beta- and gamma-decay studies of neutron-rich chromium, manganese, cobalt and nickel isotopes including the new isotopes 60Cr and 60gMn

Abstract A 36 mg cm 2 thick natW target was irradiated with 11.5 MeV/u 76Ge of 15 to 20 particle-nA beam intensity. On-line mass-separated samples of projectile-like neutron-rich products from multi-nucleon transfer-reactions were investigated in the region of mass 58–69 by β and γ-ray spectroscopy. The new isotope 60Cr was identified with a half-life of 0.57 (6) s and for the 60Mn ground state a half-life value of 51 (6) s was obtained. Decay schemes were constructed for 58Cr, 58Mn ( t 1 2 = 3 s ), 65,66,67Co and 69Ni. One new γ-ray was found in the decay of 59Cr. The Qβ value of 66Co was measured yielding 9.7 (5) MeV. The comparison of the measured new β half-life of 60Cr with the most recent predictions gave again an enhancement of the experimental value.

New neutron-rich 179Yb and 181,182Lu isotopes produced in reactions of 9 MeV/u 136Xe ions on tantalum and tungsten targets

Abstract The new neutron-rich isotopes 179 Yb and 181,182 Lu were produced in multinucleon transfer reactions by irradiating nat W/Ta targets with 9 MeV/u 136 Xe ions, and identified by mass separation and decay spectroscopy. The measured half-lives of 179 Yb, 181 Lu and 182 Lu are 8.1±0.8, 3.5±0.3 and 2.0±0.2 min, respectively. The properties of the excited states of 181,182 Hf are discussed. The possibility of studying neutron-rich nuclei outside the classical fission-product regions is demonstrated.

Decay studies of neutron-rich radium and actinium isotopes, including the new nuclides 232Ra and 232,234Ac☆

Abstract Isotopes of the elements francium to neptunium were produced in multinucleon-transfer reactions of 11.4 MeV/u 238 U ions with nat W/Ta targets. On-line mass-separated samples were investigated by γ, X and β singles and coincidence measurements. New spectroscopic information was gained on the 231 Ac decay. For the first time, β-delayed γ-rays from 232 Ra and 232,233,234 Ac were observed. Decay schemes for these isotopes are presented, and half-lives of the latter four nuclides were determined to be 250(50) s, 119(5) s, 145(10) s and 44(7) s, respectively. The comparison with theoretical half-life predictions gave remarkable agreement with gross-theory calculations.

Longitudinal and transverse momentum distributions of 9Li fragments from break-up of 11Li

Transverse and longitudinal momentum distributions of Li-9 fragments from Li-11 break-up reactions in C, Al and Pb targets have been measured at 280 MeV/u. The two-neutron removal cross-section was measured to be sigma(-2n), = 0.26 +/- 0.02 b for the carbon target, sigma(-2n) = 0.47 +/- 0.08 b for the aluminum target and sigma(-2n), = 1.9 +/- 0.4 b for the lead target. No significant difference is observed between the narrow widths (FWHM approximate to 47 MeV/c) of the transverse and longitudinal momentum distributions of the Li-9 fragments. The physical implications of this are discussed.

Investigation of neutron-rich rare-earth nuclei including the new isotopes 177Tm and 184Lu☆

Abstract Decays of neutron-rich isotopes in the rare-earth region were studied by means of on-line mass separation and β − γ spectroscopy using multinucleon-transfer reactions between beams of 136 Xe (9 and 11.7 MeV/u), 186 W (11.7 and 15 MeV/u) and 238 U (11.4 MeV/u) and targets of nat W and Ta. The higher beam energies appear to be advantageous for the production of such isotopes. Two new isotopes were identified: 177 Tm with a half-life T 1 2 = 85 −15 +10 s , and 185 Lu with T 1 2 ≈ 18 s . A new 47 s activity found at A = 171 is tentatively assigned to the decay of the new isotope 171 Ho. The properties of the ground and excited states of neutron-rich lanthanide isotopes are interpreted within the shell model using the deformed Woods-Saxon potential. A change of the ground-state configuration for odd-mass neutron-rich lutetium isotopes from π 7 2 + [404] to π 9 2 − [514] is suggested, this change being due to the influence of a large hexadecapole deformation. The role of the possible isomeric state in 180 Lu for the nucleosynthesis of 180m Ta is discussed.

Beta decay of neutron-deficient even-mass indium isotopes: Evidence for population of highly-excited states in the cadmium-daughter nuclei

Abstract By using mass-separated sources, positrons as well as β-delayed protons and γ-rays were measured from the β-decay of 102 In ( T 1 2 = 22 ± 1 s ) and 100 In ( T 1 2 = 6.1 ± 0.9 s ). In particular, the average β + (β + + EC ) ratio for the decay of 102 In was measured to be 0.76(4) and the level scheme of 102 Cd was extended. Whereas no direct β + EC feeding of the identified 102 Cd levels was observed, there is evidence for population of 102 Cd states at high excitation energy followed by statistical γ-decay. This feature, which has been deduced on the basis of the measured positron spectrum and the measured β + (β + + EC ) ratio of the 102 In decay, is compared to the decay properties of the heavier odd-odd indium isotopes 104 In, 106 In and 108 In, and is also used to interpret the observed β-delayed proton data of 102 In and 100 In. For the first time, large-space shell-model calculations have been performed for the Gamow-Teller decay of heavy odd-odd nuclei. The decay results from these calculations are in good overall agreement with the gross decay properties of 102 In and 100 In deduced from the experiment.

Decay properties of the new isotopes94Ag and95Ag

By using a40Ca beam of the UNILAC accelerator the new isotopes94Ag and95Ag were produced through58Ni(40Ca,p3n) and58Ni(40Ca,p2n) reactions, respectively, and identified by detectingβ-delayed protons from mass-separated sources.94Ag represents the heaviest N=Z nucleus with known decay properties. Theβ-decay half-lives of94Ag and95Ag were determined to be 0.42±0.05 s and 2.0±0.1 s, respectively. The measuredβ-decay properties are compared with model predictions.