Proof of residence of primeval technetium

据判断，几乎不可能直接证实在核合成时期形成的原始锝的存在。因此，努力集中在检测灭绝的原始Tc。Z=43的锝有两种长寿命放射性同位素，^<97>Tc，T_&lt;1/2&gt;=3* 10^6 y（EC）和^<98>Tc_&lt;1/2&gt;=4* 10^6 y（β ^-）。因此，从简单的观点看，直接的途径是对Ru和Mo的同位素组成进行高精度的测量<44><42>，但考虑到Z=40-44附近的半衰期效应和复杂的核合成过程，Zr的同位素研究<40>也很重要。高纯度的化学分离的任何微量元素，钌，钼和锆，以及随后的灵敏的高精度质谱是困难的工作要提前开发。通过对微量元素同位素组成的研究，得出以下结论。(1)至于 ...更多信息 地球样品中Mo的同位素变化较小，而铁陨石中Mo同位素比值的相对变化较好地反映了核合成过程，与理论相当吻合。其中一颗铁陨石被认为表明了已消失的^ Tc的影响<97>。(2)来自地球的Zr保持了长寿命Nb同位素衰变和核合成的同位素不均匀性。(3)对于Ru，最困难的是发展从铁陨石中化学分离的方法和稳定灵敏的质谱。我们对^ Ru的测量<98>可以解释为^ Tc衰变的显著影响<98>。考虑到这一结果的重要性，除了质谱法之外，还需要进一步改进回收和纯化。已经开发出用于检查同位素畸变的复杂计算机程序。总的来说，已澄清了一个焦点的灭绝锝，这使得有希望的这一主题。作为这些研究的重要副产品，我们成功地完成了以下工作：（1）地球化学估算了^ Zr的双β衰变半衰期<96>;（2）利用^<16>O-富氧消除了氧同位素的同量异位素干扰;（3）显著改进了Re-Os定年和Os的高精度同位素测量。

It has been judged virtually impossible to confirm directly the current presence of primeval technetium which was formed at the period of nucleosynthesis. Accordingly, efforts were concentrated on detection of extinct primeval Tc. Technetium with Z=43 has two long-lived radioactive isotopes, ^<97>Tc with T_<1/2>=3*10^6y(EC) and ^<98>Tc_<1/2>=4*10^6y(beta^-). Accordingly, from a simple viewpoint of extinct nuclides, the direct approach would be to make high-precision measurement of isotopic compositions of _<44>Ru and _<42>Mo, but in relation with half-life effect and the complex processes of nucleosynthesis around Z=40-44, the isotopic studies on _<40>Zr is also of importance. Chemical separation with high purity of any of trace elements, Ru, Mo and Zr, and subsequent sensitive high-precision mass spectrometry were difficult works to be developed in advance. Based on the studies on isotopic compositions of trace elements in question, the following conclusions were obtained. (1) As for … More Mo, the isotopic variation in terrestrial samples (molybdenites) is small, while the relative variation of isotopic ratios of Mo in iron meteorites refects well the process of nucleosynthesis, in considerably good agreement with the theory. One of the iron meteorites is considered to indicate the effect of extinct ^<97>Tc. (2) Zr from the earth was revealed to keep the isotopic heterogeneity which originates from decays of long-lived Nb isotopes as well as the nucleosynthesis. (3) For Ru, it was the most difficult to develop the method for chemical separation from iron meteorites and the stable sensitive mass spectrometry. Our measurement about ^<98>Ru can be interpreted to indicate the significant effect of ^<98>Tc decay. Taking into account the importance of this result, further improvement in recovery and purification is desired in addition to that in mass spectrometry. Sophisticated computer programming for examination of isotopic aberrations has been developed. Taken altogether, a focal point of extinct technetium has been clarified, which makes promising this subject. As remarkable byproducts from these studies, we succeeded in the following works : (1) geochemical estimation of half-life of double beta decay of ^<96>Zr ; (2) utilization of ^<16>O-enriched oxygen to dispense from the isobaric interferences due to oxygen isotopes ; (3) outstanding improvement of Re-Os dating and of high-precision isotopic measurement of Os. Less