A. Piechaczek

Beams of short lived nuclei produced by selective laser ionization in a gas cell

Abstract An on-line laser ion source has been developed for the production of elemental and isobaric pure beams of radioactive ions. It is based on selective resonant laser ionization of nuclear reaction products thermalized and neutralized in a noble gas at high pressure. The ion source has been tested in a wide range of recoil energies going from 1.3 MeV to ∼ 90 MeV. Efficient schemes of two step laser ionization through autoionizing states have been found for nickel, cobalt and rhodium. Residence times of the reaction products in a gas cell have been measured for helium and argon as buffer gas. Elementally pure beams of 54,55Ni and 54Co, produced in a light-ion induced fusion-evaporation reaction, and of 113Rh, produced in proton-induced fission of 238U, were obtained. An efficiency of the ion source of 6.6% for fusion reactions and of 0.22% for fission reactions has been obtained. A selectivity of the ion source of 300 for fusion and 50 for fission reactions has been achieved.

The SPIG, improvement of the efficiency and beam quality of an ion-guide based on-line isotope separator

Abstract A SPIG (Sextupole Ion Beam Guide) has been constructed and tested to couple an ion-guide based ion source to an on-line isotope separator. In comparison to a skimmer, the SPIG offers both an increased beam quality and the possibility to operate the ion-guide at higher buffer gas pressures.

Elastic 2n-transfer in the 4He(6He,6He)4He scattering

The elastic scattering He-4(He-6,He-6)He-4 has been investigated at center-of-mass energies of 11.6 and 15.9 MeV. Differential cross sections are determined using a post-accelerated He-6 (T-1/2 = 0.807 s) beam in the center-of-mass angular range between 50 and 140 degrees. The comparison of the measured data with calculations using a double folding potential shows evidence for the 2n-transfer process in the He-4(He-6,He-6)He-4 elastic scattering

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.

Beta decay of 103In: Evidence for the Gamow-Teller resonance near 100Sn

Abstract The β decay of the neutron-deficient isotope 103 In was investigated by using total absorption γ-ray spectrometry on mass-separated sources. The measurement reveals a high-lying resonance of the β-decay strength in striking disagreement with high-resolution γ-ray data. The result is discussed in comparison with shell-model predictions.

Production of 114Ba in 58Ni + 58Ni reactions and detection of its cluster radioactivity

Abstract The on-line mass separator at the GSI Unilac was used to produce and analyze decays of light barium isotopes including 114 Ba. We report the observation of 12 C emission by 114 Ba. The halflives for 12 C and alpha emission are found to be ∼1.7 × 10 4 s and 500 s respectively.

Decay studies of the neutron-deficient isotopes 114–118Ba

The very neutron-deficient isotopes 114–118Ba were produced in 58Ni induced reactions on 58Ni, 60Ni or 63Cu targets. By on-line mass separation of BaF molecules formed in the separator ion source, exceptionally pure sources of these isotopes were available for spectroscopic studies. The β-decays of 114Ba (T12 = 0.43−0.15+0.30s), 115Ba (T12 = 0.45 ± 0.05 s), 116Ba (T12 = 1.3 ± 0.2 s) and 118Ba (T12 = 5.2 ± 0.2 s) were investigated for the first time. 114Ba, 115Ba and 116Ba were identified as β-delayed proton emitters and absolute branching ratios for this decay mode were determined to be 20 ± 10%, >15%, and 3 ± 1%, respectively. In the decay study of 118Ba several γ transitions were identified. New information was also obtained on the β-delayed γ radiation of 117Ba. The spectroscopic data were used to determine the production cross-sections for all these isotopes. Results of our half-life measurements and β-delayed proton studies are confronted with theoretical predictions.

Determination of the Gamow–Teller strength function for the neutron-deficient isotopes 104–107In

Abstract The Gamow–Teller β decays of the neutron-deficient indium isotopes 104–107 In have been investigated by using total absorption γ -ray spectrometry on mass-separated sources. The experimental Gamow–Teller strength, deduced as a function of the excitation energy in the daughter nuclei 104–107 Cd, is compared to shell-model predictions.

Mono-isotopic beams of exotic nuclei produced by a universal on-line laser ion source

Abstract We report on recent experiments proving the high efficiency and selectivity of a universal and fast on-line laser ion source based on resonance laser ionization in a gas cell. The application for the production of neutron-rich nickel isotopes is discussed, including the first observation of γ-transitions from the decay of 71Ni. We also discuss current efforts to still increase both efficiency and selectivity.

Beta decay of the new isotope 101Sn

The very neutron-deficient isotope 101Sn was produced in a 50Cr(58Ni, 2p5n) reaction and its decay properties were determined for the first time. By using chemically selective ion sources of an on-line mass separator, the energy spectrum and the half-life (3 ± 1 s) of beta-delayed protons of 101Sn were measured. These results are compared to theoretical predictions.