Proof of residence of primeval technetium

人们认为，几乎不可能直接证实目前是否存在在核合成期间形成的原始氚。因此，工作集中在检测灭绝的原始TC上。Z=43的氚有两个长寿命的放射性同位素：T_&lt；1/2&gt；=3*10^6y(EC)和^&lt；98&gt；TC_&lt；1/2&gt；=4*10^6y(β^-)。因此，从已灭绝的核素的简单观点来看，直接的方法是高精度地测量_&lt；44&gt；Ru和_&lt；42&gt；Mo的同位素组成，但考虑到Z=40-44附近的半衰期效应和复杂的核合成过程，对_&lt；40&gt；Zr的同位素研究也具有重要意义。高纯度的痕量元素Ru、Mo、Zr的化学分离，以及随后灵敏的高精度质谱学都是难以预先开发的工作。在对有关微量元素的同位素组成研究的基础上，得出以下结论。(1)至于…陆地样品(辉钼矿)中钼的相对变化较小，而铁陨石中钼的相对变化较好地反映了核合成过程，与理论吻合较好。其中一块铁陨石被认为表明了灭绝的^&lt；97&gt；tc的影响。(2)地球源区的锆石具有长寿命Nb同位素衰变和核合成所致的同位素不均一性。(3)对于Ru来说，最困难的是从铁陨石中进行化学分离的方法和稳定灵敏的质谱学。我们对^&lt；98&gt；Ru的测量可以解释为^&lt；98&gt；Tc衰变的显著影响。考虑到这一结果的重要性，除了质谱学方面的改进外，还需要在回收和纯化方面进一步改进。已经开发了用于检查同位素像差的复杂的计算机程序。总而言之，已经灭绝的氚的一个焦点已经被澄清，这使得这个课题很有希望。作为这些研究的显著副产品，我们成功地完成了以下工作：(1)~t；96&gt；Zr双β衰变半衰期的地球化学估算；(2)利用^&lt；16&gt；富氧来消除氧同位素引起的同压干扰；(3)Re-Os测年和高精度Os同位素测量的显著改进。较少

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