[en] The ¹⁰Be contents measured in eight bulk samples of the Jilin meteorite range from 5.05 +- 0.55 to 16.3 +- 1.7 dpm/kg, more than three fold, and correlate with the ²¹Ne contents. A least-squares fit of these data has a positive intercept on the ¹⁰Be axis which can be explained in terms of a two-stage irradiation. The second, more recent stage lasted 0.57 +- 0.14 Myr. Model calculations give first-stage ¹⁰Be/²¹Ne ages ranging from 6.2 to 7.1 Myr. (orig.)

No abstract available

No abstract available

[en] The importance of dating very old groundwaters requires the development of new dating methods. Such methods are available using ³⁶Cl and ⁸¹Kr, but their range is limited to about 1 million years. Older fluids must be dated by in situ produced noble gas nuclides. The use of ²¹Ne is discussed for groundwaters of the north German Salzgitter District. It is likely that the use of ²¹Ne will not develop into a routine tool; nonetheless, ²¹Ne excess gives information on the level of in situ production of gases, a fact which is important for more reliable ⁴He dating. (author). 16 refs, 2 figs

[en] Nuclear-spin--polarized samples of up to 200 Torr ²¹Ne have been obtained through spin-exchange collisions with optically pumped Rb vapor. The exponential time constant associated with buildup and decay of this polarization along the quantization axis is in excess of 15 h in 3-cm-diam Pyrex cells. From the data and estimates given, samples of ²¹Ne with densities greater than 1 STP and polarization in excess of 1% appear feasible

[en] The rare stable isotope neon-21 comprises 0.27 percent of natural atmospheric neon. In earlier work, separation of neon-21 in high purity was accomplished by thermal diffusion with the aid of deuterated methane as an auxiliary gas. The separation is now being accomplished by thermal diffusion without the use of an auxiliary gas. In the latter process a two-stage, multiple column, thermal diffusion system is employed. The most abundant isotope, neon-20, is removed in the first stage, leaving a binary mixture of neon-21 and neon-22. The binary mixture is further separated in the second stage of the process, yielding high purity neon-21. It was found that the performance of the separation apparatus in both the transient and steady-state modes could be accurately predicted from thermal diffusion column and cascade theory. The thermal diffusion separation technique can be used for the separation of a wide variety of gas mixtures, including isotopic separations of stable and radioactive nuclides. Recent examples include separation of argon-37 and argon-39 from atmospheric argon and the enrichment of krypton-85 and xenon-136 from nuclear reactor fission gas

No abstract available

[en] Energy levels of ²¹Ne up to 6.76 MeV are studied by measuring the thermal neutron capture gama rays from natural neon. A Ge(Li) detector is used. Energies and intensities are measured relative to calibration lines of nitrogen. The Q-value and the cross section of the reaction ²⁰Ne(n,γ)²¹Ne are calculated. The proposed level scheme is discussed in terms of the Nilsson model, considering the coupling of one particle to the ²⁰Ne core. Coriolis coupling is taken into account for the three positive parity bands, K sup(π)=3/2⁺, 1/2⁺ and 5/2⁺. Measurements are made using the research reactor of the Instituto de Energia Atomica

[en] Cosmogenic neon in sodium-rich oligoclase feldspar from the ordinary chondrites St.Severin and Guarena is characterized by an unusually high ²²Ne/²¹Ne=1.50+-0.02. This high ratio is due to the cosmogenic ²²Ne/²¹Ne production ratio in sodium which is 2.9+-0.3,two to three times the production ratio in any other target element. The relative production rate of ²¹Ne per gram sodium is one quarter the production rate per gram magnesium. The striking enrichment of ²²Ne relative to ²¹Ne in sodium arises from enhanced indirect production from ²³Na via ²²Na. The unusual composition of cosmogenic neon in sodium and sodium-rich minerals explains the high²²Ne/²¹Ne ratios observed in inclusions of the Allende carbonaceous chondrite, and observed during low temperature extractions of neon from ordinary chondrites. The isotopic composition of cosmogenic neon released during the stepwise heating of a trapped gas-rich meteorite containing sodium-rich phases can be expected to vary, and use of a constant cosmogenic neon composition to derive the composition of the trapped gas may not be justified. Preferential loss of this ²²Ne-enriched cosmogenic neon from meteoritic feldspar can result in a 2-3% drop in the measured cosmogenic ²²Ne/²¹Ne ratio in a bulk meteorite sample. This apparent change in composition can lead to overestimation of the minimum pre-atmospheric mass of the meteorite by a factor of two. (Auth.)

[en] In the Argentine Andes and the adjacent foreland between 24^o and 28^o more than 50 landslide deposits with volumes between 10⁶ and 4x10⁸ m³ have been identified, either in narrow valleys or on broad piedmont areas (Hermanns and Strecker, 1999). Dating such catastrophic mass movements is essential for assessing the frequency of landslides as well as possible conditioning and triggering mechanisms. However, deriving a chronology of such events is difficult in the arid to semi-arid regions of northwestern Argentina, where landslide deposits are often void of ¹⁴C-datable material. In-situ-produced nuclides in rocks exposed to cosmic ray irradiation after the landslide event, either on the breakaway scarp or on the surface of the deposit, provide an alternative dating tool. The scope of the present work is to reveal the frequency of giant landslides along a tectonically active mountain front. The Sierra Laguna Blanca (hereafter SLB; 26^o30', 67^o10'W) in the Puna plateau of the Southern Central Andes represents an ideal location for this study, because its western piedmont comprises ten large landslide deposits of the rockavalanche type. Eight of them are laterally superposed, providing relative age control. In addition, four reverse faults with important displacement indicate sustained Neogene to Quaternary tectonic activity of this mountain front. The high elevation of ∼4000 m and a prevailing dry climate throughout the Quaternary in this area (Fox and Strecker, 1991) render these landslide deposits well-suited for cosmic ray exposure dating (au)