D. Schardt

New neutron-deficient tellurium, iodine, and xenon isotopes produced by reactions of 290 MeV 58Ni ions on 58Ni and 63Cu targets

Abstract The new neutron-deficient nuclei 108–110 Te, 110–114 I, and 114 Xe were produced as evaporation residues from reactions of 290 MeV 58 Ni ions on 58 Ni and 63 Cu targets and identified by mass separation and subsequent decay spectroscopy. The isotopes 108 Te, 109 Te, 110 I, and 111 I form a new region of α-particle decay. The decay data are compared with predictions for nuclear masses and half-lives.

Alpha decay studies of tellurium, iodine, xenon and cesium isotopes☆

Abstract Very neutron-deficient isotopes in the trans-tin region were produced by reactions of 290 MeV 58 Ni ions on 58 Ni targets, and studied by on-line mass separation at GSI. Twelve α-emitters — 107–110 Te, 110–113 I, 111–113 Xe, 114 Cs — were identified. Systematics of Q α values and reduced α-widths for this new island of α-emission are discussed.

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.

Alpha decay of neutron-deficient isotopes with 78 ⪕ Z ⩽ 83 including the new isotopes 183, 184Pb and 188Bi

Abstract Using on-line mass separation of evaporation residues from heavy-ion-induced fusion reactions, three new isotopes were identified by their alpha decay, E α given in keV: 183 Pb, 6715(20), 184 Pb, 6632(10) and 188 Bi, 6820(20). Half-lives were determined for 184 Pb, 0.55(6)s, 185 Pb, 4.1(3)s and 183 Tl, 0.060(15) s. The alpha branching ratios were re-measured for 182–184 Hg and 178, 179 Pt, the results are discussed within the framework of alpha width systematics.

A new island of α-emission: α-decay energies and widths of neutron deficient tellurium, iodine and xenon isotopes

Abstract Using on-line mass separation, eight α-emitters (given with their α-decay energies in keV) in the trans-tin region were investigated: 108Te, 3300(30); 109Te, 3080(15); 110I, 3424(15); 111I, 3150(30); 112I, 2866(50); 112Xe, 3185(30); 113Xe, 2990(30); 114Cs (or 114Ba), 3226(30). Systematics of Q α values and reduced α-widths for this new island of α-emission are discussed.

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.

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.

The decay of 0.57 s114Cs

Fusion reactions between58Ni projectiles and58Ni target nuclei were used to produce114Cs activity, which was studied by on-line mass separation and decay spectroscopy. The obtained half-life of 0.57±0.02 s and the probability ratio of 44±3 between betadelayed proton and beta-delayed alpha emission represent data with improved precision. The absolute branching ratios for both particle decay modes were determined to be (7 ±2)×10−2 and (1.6±0.6)×10−3, respectively. These branching ratios and the shapes of particle spectra are discussed with reference to the statistical model calculations. Groundstate alpha decay of114Cs was observed with an alpha energy of 3,226±30 keV and a branching ratio of (1.8±0.6)×10−4. An upper limit of the branching ratio for a possible ground-state proton decay was set at 5×10−4. Fromγ-ray singles andγ-γ coincidence measurements, excited states in114Xe are proposed.

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.

Direct proton decay of 0.56-s147Tm and search for this decay mode among very neutron-deficient isotopes with 53≦Z≦67

The earlier preliminary assignment of a 1,055±6 keV proton line to direct proton decay of147Tm is supported by cross bombardment measurements and by a negative result from a positron-proton coincidence experiment. The half-life was remeasured to be 0.56 ±0.04s. For two types of thermal ion sources, overall efficiencies were estimated for on-line mass separation of known short-lived isotopes of promethium, europium, terbium, and holmium. Direct proton decay was searched for among very neutron-deficient isotopes of these elements, and of iodine and caesium. No evidence for direct proton decay was found. Based on estimated overall efficiencies, on calculated cross-sections, and on predictions from the gross-theory ofβ decay, half-life limits for direct proton decay were deduced.