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For the time period from 1.5 to 4 Myr before the present we found in deep ocean ferromanganese crusts a ^{53}Mn excess concentration in terms of ^{53}Mn/Mn of about 4×10^{-14} over that expected for cosmogenic production. We conclude that this ^{53}Mn is of supernova origin because it is detected in the same time window, about 2.5 Myr ago, where ^{60}Fe has been found earlier. This overabundance confirms the supernova origin of that ^{60}Fe. For the first time, supernova-formed ^{53}Mn has been detected and it is the second positively identified radioisotope from the same supernova. The ratio ^{53}Mn/^{60}Fe of about 14 is consistent with that expected for a SN with a 11-25 M_{⊙} progenitor mass and solar metallicity.

For the time period from 1.5 to 4 Myr before the present we found in deep ocean ferromanganese crusts a ^{53}Mn excess concentration in terms of ^{53}Mn/Mn of about 4×10^{-14} over that expected for cosmogenic production. We conclude that this ^{53}Mn is of supernova origin because it is detected in the same time window, about 2.5 Myr ago, where ^{60}Fe has been found earlier. This overabundance confirms the supernova origin of that ^{60}Fe. For the first time, supernova-formed ^{53}Mn has been detected and it is the second positively identified radioisotope from the same supernova. The ratio ^{53}Mn/^{60}Fe of about 14 is consistent with that expected for a SN with a 11-25 M_{⊙} progenitor mass and solar metallicity.

The $^{58}\mathrm{Ni}(n,\ensuremath{\gamma})^{59}\mathrm{Ni}$ cross section was measured with a combination of the activation technique and accelerator mass spectrometry (AMS). The neutron activations were performed at the Karlsruhe 3.7 MV Van de Graaff accelerator using the quasistellar neutron spectrum at $kT=25$ keV produced by the $^{7}\mathrm{Li}(p,n)^{7}\mathrm{Be}$ reaction. The subsequent AMS measurements were carried out at the 14 MV tandem accelerator of the Maier-Leibnitz Laboratory in Garching using the gas-filled analyzing magnet system (GAMS). Three individual samples were measured, yielding a Maxwellian-averaged cross section at $kT=30$ keV of ${\ensuremath{\langle}\ensuremath{\sigma}\ensuremath{\rangle}}_{30\phantom{\rule{0.16em}{0ex}}\text{keV}}$ = 30.4 (23)${}^{\mathrm{syst}}$(9)${}^{\mathrm{stat}}$ mbarn. This value is slightly lower than two recently published measurements using the time-of-flight (TOF) method, but agrees within the uncertainties. Our new results also resolve the large discrepancy between older TOF measurements and our previous value.

In contrary to siliceous environments, there is a severe lack of cosmogenic nuclides, that can be used for in situ dating of calcareous environments. Thus, we have investigated other nuclides than 36 Cl as possible dating tools by cross-calibration. Cosmogenic 10 Be is highly contaminated with atmospheric 10 Be and cannot be removed quantitatively, even by a very sophisticated chemical cleaning procedure. Only working on clay-free calcite provides correct 10

The importance of 10 Be in different applications of accelerator mass spectrometry (AMS) is well-known. In this context the half-life of 10 Be has a crucial impact, and an accurate and precise determination of the half-life is a prerequisite for many of the applications of 10 Be in cosmic-ray and earth science research. Recently, the value of the 10 Be half-life has been the centre of much debate. In order to overcome uncertainties inherent in previous determinations, we introduced a new method of high accuracy and precision. An aliquot of our highly enriched 10 Be master solution was serially diluted with increasing well-known masses of 9 Be. We then determined the initial 10 Be concentration by least square fit to the series of measurements of the resultant 10 Be/ 9 Be ratio. In order to minimize uncertainties because of mass bias which plague other low-energy mass spectrometric methods, we used for the first time Heavy-Ion Elastic Recoil Detection (HI-ERD) for the determination of the 10 Be/ 9 Be isotopic ratios, a technique which does not suffer from difficult to control mass fractionation. The specific activity of the master solution was measured by means of accurate liquid scintillation counting (LSC). The resultant combination of the 10 Be concentration and activity yields a 10 Be half-life of T 1/2 = 1.388 ± 0.018 (1 s, 1.30%) Ma. In a parallel but independent study (Chmeleff et al. [11] ), found a value of 1.386 ± 0.016 (1.15%) Ma. Our recommended weighted mean and mean standard error for the new value for 10 Be half-life based on these two independent measurements is 1.387 ± 0.012 (0.87%) Ma.

The energy averaged ( n , γ ) cross sections of 58 Ni and 78 Se at a stellar energy of kT = 25 keV have been investigated with the so called activation technique, which represents a well established tool for measurements of stellar neutron cross sections. For both nuclides, offline decay counting is prohibitive due to the long half-lives of the reaction products as well as the absence of suitable γ-ray transitions. The measurements reported here are, therefore, based on accelerator mass spectrometry (AMS) determination of the number of 59 Ni and 79 Se nuclei produced by irradiation of Ni and Se targets in a quasi-stellar neutron spectrum. We present in this paper preliminary results of σ exp ( kT = 25 keV) = 27.2 ± 1.8 mb and 61 ± 10 mb for neutron capture cross sections of 58 Ni and 78 Se, respectively.

Our AMS system, with the gas-filled detector system GAMS, has been optimized for measurements with 53 Mn. A high sensitivity has been achieved. A newly installed cesium sputter ion source yields an improved emittance, and thus a higher mass resolution. By the extraction of the manganese molecule MnF − instead of MnO − we can suppress the isobaric chromium background in the ion source by more than a factor of three. The GAMS system achieves an isobaric suppression factor of about 3 × 10 8 . Measurements on blank samples yielded upper limits for the 53 Mn/ 55 Mn ratios of 7 × 10 −15 .

With a half-life of 81.1$\phantom{\rule{0.16em}{0ex}}$Myr, ${}^{244}$Pu could be both the heaviest and the shortest-lived nuclide present on Earth as a relic of the last supernova(e) that occurred before the formation of the Solar System. Hoffman et al. [Nature (London) 234, 132 (1971)] reported on the detection of this nuclide ($1.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}$ g ${}^{244}$Pu/g) in the rare-earth mineral bastn\"asite with the use of a mass spectrometer. Up to now these findings were never reassessed. We describe the search for primordial ${}^{244}$Pu in a sample of bastn\"asite with the method of accelerator mass spectrometry (AMS). It was performed with a highly sensitive setup, identifying the ions by the determination of their time-of-flight and energy. Using AMS, the stripping to high charge states allows the suppression of any molecular interference. During our measurements we observed no event of ${}^{244}$Pu. Therefore, we can give an upper limit for the abundance of ${}^{244}$Pu in our sample of the mineral bastn\"asite of 370 atoms per gram ($1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}$ g ${}^{244}$Pu/g). The concentration of ${}^{244}$Pu in our sample of bastn\"asite is significantly lower than the previously determined value.

Quartz represents one of the most widespread minerals and is widely used in geosciences to reconstruct physic-chemical conditions of rock and mineral formation. However, interpretation of analytical data may be limited by the ability of quartz to regenerate during secondary alteration processes occurring under metamorphic or hydrothermal conditions. This behaviour distinguishes quartz from most minerals commonly associated with. Primary genetic information is obliterated during quartz regeneration. This includes features related to the real structure of quartz, but also to fluid and mineral inclusions. The present contribution examines examples covering various fields of mineral research, namely the genetic interpretation of trace element content in quartz, quartz provenance analysis using cathodoluminescence (CL) colour imaging, and the analysis of mineral and fluid inclusions in quartz. It is demonstrated in all cases that care needs to be taken when interpreting genetic information encoded. Distinction of features related to primary growth or secondary alteration is not simple and requires application of complementary analytical techniques.

An accurate knowledge of the neutron capture cross sections of 62,63Ni is crucial since both isotopes take key positions which affect the whole reaction flow in the weak s process up to A=90. No experimental value for the 63Ni(n,gamma) cross section exists so far, and until recently the experimental values for 62Ni(n,gamma) at stellar temperatures (kT=30 keV) ranged between 12 and 37 mb. This latter discrepancy could now be solved by two activations with following AMS using the GAMS setup at the Munich tandem accelerator which are also in perfect agreement with a recent time-of-flight measurement. The resulting (preliminary) Maxwellian cross section at kT=30 keV was determined to be 30keV = 23.4 +/- 4.6 mb. Additionally, we have measured the 64Ni(gamma,n)63Ni cross section close to threshold. Photoactivations at 13.5 MeV, 11.4 MeV and 10.3 MeV were carried out with the ELBE accelerator at Forschungszentrum Dresden-Rossendorf. A first AMS measurement of the sample activated at 13.5 MeV revealed a cross section smaller by more than a factor of 2 compared to NON-SMOKER predictions., Comment: Proceedings of the 11th International Conference on Accelerator Mass Spectrometry in Rome, Sept. 14-19, 2008; to be published in Nucl. Instr. Meth. A

We have made a new determination of the half-life of the radioactive isotope $^{60}\mathrm{Fe}$ using high precision measurements of the number of $^{60}\mathrm{Fe}$ atoms and their activity in a sample containing over ${10}^{15}$ $^{60}\mathrm{Fe}$ atoms. Our new value for the half-life of $^{60}\mathrm{Fe}$ is $(2.62\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }\mathrm{yr}$, significantly above the previously reported value of $(1.49\ifmmode\pm\else\textpm\fi{}0.27)\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }\mathrm{yr}$. Our new measurement for the lifetime of $^{60}\mathrm{Fe}$ has significant implications for interpretations of galactic nucleosynthesis, for determinations of formation time scales of solids in the early Solar System, and for the interpretation of live $^{60}\mathrm{Fe}$ measurements from supernova-ejecta deposits on Earth.

We have made a new determination of the half-life of the radioactive isotope 60Fe using high precision measurements of the number of 60Fe atoms and their activity in a sample containing over 10(15) 60Fe atoms. Our new value for the half-life of 60Fe is (2.62+/-0.04) x 10(6) yr, significantly above the previously reported value of (1.49+/-0.27) x 10(6) yr. Our new measurement for the lifetime of 60Fe has significant implications for interpretations of galactic nucleosynthesis, for determinations of formation time scales of solids in the early Solar System, and for the interpretation of live 60Fe measurements from supernova-ejecta deposits on Earth.

The s process synthesizes the elements between Fe and Sr in massive stars during two major evolutionary stages, convective core He burning and C shell burning. This scenario implies fascinating consequences for the chemical evolution of the star. For instance, the neutron capture rate at each isotope can have a big influence on the production of many of the subsequent higher mass isotopes. Correspondingly, one needs to know the (n,γ) cross sections of the involved isotopes with high accuracy in order to determine the abundance pattern reliably and to obtain a consistent picture of this stage. This contribution gives an overview on recent and future experiments for the Fe/Ni nucleosynthesis in massive stars. New results on 60Fe, 62Ni and 64Ni are reported. 60Fe is mostly produced during the short convective C shell burning phase, where peak densities of ∼1011 cm−3 are reached, prior to the SN explosion. The stellar (n,γ) cross section of 60Fe could be measured with a 1 μg sample obtained at PSI (Switzerlan...

The discovery of naturally occurring long-lived isomeric states (t_1/2 > 10^8 yr) in the neutron-deficient isotopes 211,213,217,218Th [A. Marinov et al., Phys. Rev. C 76, 021303(R) (2007)] was reexamined using accelerator mass spectrometry (AMS). Because AMS does not suffer from molecular isobaric background in the detection system, it is an extremely sensitive technique. Despite our up to two orders of magnitude higher sensitivity we cannot confirm the discoveries of neutron-deficient thorium isotopes and provide upper limits for their abundances., 3 pages, 1 figure

The strengths of resonances located at center-of-mass energies of ${E}_{c.m.}=189$, 304, 374, and 418 keV for the $^{25}\mathrm{Mg}$($p$,$\ensuremath{\gamma})$ reaction have been measured for the first time with an off-line method: Mg targets were firstly activated with protons at the resonance energies and the produced $^{26}\mathrm{Al}$${}^{g}$ nuclei were counted by means of highly sensitive accelerator mass spectrometry (AMS). Thus, the production of $^{26}\mathrm{Al}$ in its ground state is determined independently from the \ensuremath{\gamma}-decay branching ratio. While the 304, 374, and 418 keV resonances show fair agreement with previous measurements, the 189 keV resonance yield a significantly less strength. In addition, an experimental upper limit for the ${E}_{c.m.}=92$ keV resonance was determined.