The half-life of the neutron-rich nuclide Fe-60 has been in dispute in recent years. A measurement in 2009 published a value of (2.62 +/- 0.04) x 10(6) years, almost twice that of the previously accepted value from 1984 of (1.49 +/- 0.27) x 10(6) yr. This longer half-life was confirmed in 2015 by a second measurement, resulting in a value of (2.50 +/- 0.12) x 10(6) yr. All three half-life measurements used the grow-in of the.-ray lines in Ni-60 from the decay of the ground state of Co-60 (t(1/2) = 5.27 yr) to determine the activity of a sample with a known number of Fe-60 atoms. In contrast, the work presented here measured the Fe-60 activity directly via the 58.6 keV gamma-ray line from the short-lived isomeric state of Co-60 (t(1/2) = 10.5 min), thus being independent of any possible contamination from long-lived Co-60g. A fraction of the material from the 2015 experiment with a known number of Fe-60 atoms was used for the activity measurement, resulting in a half-life value of (2.72 +/- 0.16) x 10(6) yr, confirming again the longer half-life. In addition, Fe-60/Fe-56 isotopic ratios of samples with two different dilutions of this material were measured with accelerator mass spectrometry to determine the number of Fe-60 atoms. Combining this with our activity measurement resulted in a half-life value of (2.69 +/- 0.28) x 10(6) yr, again agreeing with the longer half-life.

The half-life of the neutron-rich nuclide, {\fesixty} has been in dispute in recent years. A measurement in 2009 published a value of $(2.62 \pm 0.04)\times10^{6}$ years, almost twice that of the previously accepted value from 1984 of $(1.49 \pm 0.27)\times10^{6}$ years. This longer half-life was confirmed in 2015 by a second measurement, resulting in a value of $(2.50 \pm 0.12)\times10^{6}$ years. All three half-life measurements used the grow-in of the $\gamma$-ray lines in {\nisixty} from the decay of the ground state of $^{60}\text{Co}$ (t$_{1/2}$=5.27 years) to determine the activity of a sample with a known number of {\fesixty} atoms. In contrast, the work presented here measured the {\fesixty} activity directly via the 58.6 keV $\gamma$-ray line from the short-lived isomeric state of $^{60}\text{Co}$ (t$_{1/2}$=10.5 minutes), thus being independent of any possible contamination from long-lived $^{60\text{g}}\text{Co}$. A fraction of the material from the 2015 experiment with a known number of {\fesixty} atoms was used for the activity measurement, resulting in a half-life value of $(2.72 \pm 0.16)\times10^{6}$ years, confirming again the longer half-life. In addition, {\fesixty}/{\fe} isotopic ratios of samples with two different dilutions of this material were measured with Accelerator Mass Spectrometry (AMS) to determine the number of {\fesixty} atoms. Combining this with our activity measurement resulted in a half-life value of $(2.69 \pm 0.28)\times 10^{6}$ years, again agreeing with the longer half-life.

The C-13(He-4, 4 alpha)n breakup reaction has been studied at beam energies of 27.0, 27.5, and 28.0 MeV. A comparison with previous measurements of the C-12(He-4, Be-8)Be-8 excitation function and C-12(O-16, 4a alpha)C-12 breakup channel suggests the Be-8(gs) + Be-8(gs) decay of O-16 is observed from a possible 2(+) state at 17.3 +/- 0.2 MeV, a 4(+) state at 18.0 +/- 0.2 MeV, a 2(+) or 4(+) state at 19.4 +/- 0.2 MeV, and a 4(+) or 6(+) state at 21.0 +/- 0.2 MeV. The 2(+) or 4(+) assignment for the (19.4 +/- 0.2)-MeV state appears to be supported by the relative cross sections expected for resonant and sequential breakup reactions.

Equilibrium charge state distributions of stable 60Ni, 59Co, and 63Cu beams passing through a 1 μm thick Mo foil were measured at beam energies of 1.84 MeV/u, 2.09 MeV/u, and 2.11 MeV/u respectively. A 1-D position sensitive Parallel Grid Avalanche Counter detector (PGAC) was used at the exit of a spectrograph magnet, enabling us to measure the intensity of several charge states simultaneously. The number of charge states measured for each beam constituted more than 99% of the total equilibrium charge state distribution for that element. Currently, little experimental data exists for equilibrium charge state distributions for heavy ions with 19≲Zp,Zt≲54 (Zp and Zt, are the projectile's and target's atomic numbers respectively). Hence the success of the semi-empirical models in predicting typical characteristics of equilibrium CSDs (mean charge states and distribution widths), has not been thoroughly tested at the energy region of interest. A number of semi-empirical models from the literature were evaluated in this study, regarding their ability to reproduce the characteristics of the measured charge state distributions. The evaluated models were selected from the literature based on whether they are suitable for the given range of atomic numbers and on their frequent use by the nuclear physics community. Finally, an attempt was made to combine model predictions for the mean charge state, the distribution width and the distribution shape, to come up with a more reliable model. We discuss this new "combinatorial" prescription and compare its results with our experimental data and with calculations using the other semi-empirical models studied in this work.

B. Bucher, 2, ∗ X. D. Tang, † X. Fang, A. Heger, ‡ S. Almaraz-Calderon, § A. Alongi, A. D. Ayangeakaa, ¶ M. Beard, A. Best, ∗∗ J. Browne, C. Cahillane, M. Couder, R. J. deBoer, A. Kontos, L. Lamm, †† Y. J. Li, A. Long, W. Lu, S. Lyons, M. Notani, D. Patel, N. Paul, M. Pignatari, 7, ‡ A. Roberts, D. Robertson, K. Smith, E. Stech, R. Talwar, W. P. Tan, M. Wiescher, and S. E. Woosley Institute for Structure and Nuclear Astrophysics, Joint Institute for Nuclear Astrophysics, University of Notre Dame, Notre Dame, Indiana 46556, USA Lawrence Livermore National Laboratory, Livermore, California 94550, USA Institute of Modern Physics, Chinese Academy of Science, Lanzhou, Gansu 730000, P.R. China Monash Center for Astrophysics, School of Mathematical Sciences, Monash University, Victoria 3800, Australia China Institute of Atomic Energy, Beijing 102413, P.R. China Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklos ut 15-17, H-1121 Budapest, Hungary Department of Physics, University of Basel, Basel, CH-4056, Switzerland Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA (Dated: July 15, 2015)

Equilibrium charge state distributions of stable 60Ni, 59Co, and 63Cu beams passing through a 1um thick Mo foil were measured at beam energies of 1.84 MeV/u, 2.09 MeV/u, and 2.11 MeV/u respectively. A 1-D position sensitive Parallel Grid Avalanche Counter detector (PGAC) was used at the exit of a spectrograph magnet, enabling us to measure the intensity of several charge states simultaneously. The number of charge states measured for each beam constituted more than 99% of the total equilibrium charge state distribution for that elements. Currently, little experimental data exists for equilibrium charge state distributions for heavy ions with 19

93Zr with a half-life of 1.6Ma is produced with high yield in nuclear fission, and thus should be present as a natural or anthropogenic trace isotope in all compartments of the general environment. Sensitive measurements of this isotope would immediately find numerous applications, however, its detection at sufficiently low levels has not yet been achieved. AMS measurements of 93Zr suffer from the interference of the stable isobar 93Nb. At the Vienna Environmental Research Accelerator VERA a new multi-anode ionization chamber was built. It is optimized for isobar separation in the medium mass range and is based on the experience from AMS experiments of 36Cl at our 3-MV tandem accelerator facility. The design provides high flexibility in anode configuration and detector geometry. After validating the excellent energy resolution of the detector with 36S, it was recently used to study iron–nickel and zirconium–niobium–molybdenum isobar separation. To our surprise, the separation of 94Zr (Z=40) from 94Mo (Z=42) was found to be much better than that of 58Fe (Z=26) from 58Ni (Z=28), despite the significantly larger ΔZ/Z of the latter pair. This clearly contradicts results from SRIM-simulations and suggests that differences in the stopping behavior may unexpectedly favor identification of 93Zr. At 24MeV particle energy, a 93Nb (Z=41) suppression factor of 1000 is expected based on a synthetic 93Zr spectrum obtained by interpolation between experimental spectra from the two neighboring stable isotopes 92Zr and 94Zr. Assuming realistic numbers for chemical niobium reduction, a detection level of 93Zr/Zr below 10−9 seems feasible.

Short-lived radionuclides (SLRs) with lifetimes tau < 100 Myr are known to have been extant when the Solar System formed over 4.5 billion years ago. Identifying the sources of SLRs is important for understanding the time scales of Solar System formation and processes that occurred early in its history. Extinct Cl-36 (t(1/2) = 0.301 Myr) is thought to have been produced by interaction of solar energetic particles, emitted by the young Sun, with gas and dust in the nascent Solar System. However, models that calculate SLR production in the early Solar System lack experimental data for the Cl-36 production reactions. We present here the first measurement of the cross section of one of the main Cl-36 production reactions, S-33(a, p)Cl-36, in the energy range 0.70-2.42 MeV/nucleon. The cross-section measurement was performed by bombarding a target and collecting the recoiled Cl-36 atoms produced in the reaction, chemically processing the samples, and measuring the Cl-36/Cl ratio of the activated samples with accelerator mass spectrometry. The experimental results were found to be systematically higher than the cross sections used in previous local irradiation models and other Hauser-Feshbach calculated predictions. However, the effects of the experimentally measured cross sections on the modeled production of Cl-36 in the early Solar System were found to be minimal. Reaction channels involving S targets dominate Cl-36 production, but the astrophysical event parameters can dramatically change each reaction's relative contribution.

Short-lived radionuclides (SLRs) with lifetimes \tau < 100 Ma are known to have been extant when the Solar System formed over 4.5 billion years ago. Identifying the sources of SLRs is important for understanding the timescales of Solar System formation and processes that occurred early in its history. Extinct 36Cl (t_1/2 = 0.301 Ma) is thought to have been produced by interaction of solar energetic particles (SEPs), emitted by the young Sun, with gas and dust in the nascent Solar System. However, models that calculate SLR production in the early Solar System (ESS) lack experimental data for the 36Cl production reactions. We present here the first measurement of the cross section of one of the main 36Cl production reactions, 33S(\alpha,p)36Cl, in the energy range 0.70 - 2.42 MeV/A. The cross section measurement was performed by bombarding a target and collecting the recoiled 36Cl atoms produced in the reaction, chemically processing the samples, and measuring the 36Cl/Cl ratio of the activated samples with accelerator mass spectrometry (AMS). The experimental results were found to be systematically higher than the cross sections used in previous local irradiation models and other Hauser-Feshbach calculated predictions. However, the effects of the experimentally measured cross sections on the modeled production of 36Cl in the early Solar System were found to be minimal. Reactions channels involving S targets dominate 36Cl production, but the astrophysical event parameters can dramatically change each reactions' relative contribution.