Search for Extra-Solar Materials as Carriers of Anomalous Noble Gas Isotopes in Meteorites

1.根据Heymann等人的恒星模型预测，进一步探讨了异常同位素组成的陨石稀有气体同位素的核合成起源。我们的三同位素分析揭示了S过程和r过程同位素的特征，并表明核合成模型在解释观测到的稀有气体丰度异常方面很有希望。恒星的光解条件与我们先前推导的相同，即在T_9=2.05的峰值温度下，硅的烧制时间为(6.5×0.5)×10^4秒才能产生(？)^&lt；126&gt；Xe)_p=2.10.2和观测到的重Xe比率，以限制爆炸相的条件具有3.8x10^&lt；-7&gt；[摩尔/cm^3秒]产生(^&lt；134&gt；xe/^&lt；136&gt；xe)_r=0.675。S和r-(&p-)同位素的载流相(S)最近被分别指定为非常微小的碳化硅和钻石，但仍在争论中(见下文3)。高能光子…此外，与高通量的中子一起，似乎对超新星爆炸时化学元素的再处理起到了作用。为了探索这种可能性，在30-1000 MeV的韧致辐射终点能量范围内，系统地研究了13个靶核的光致伸缩、光碎裂、光裂变和光子化反应。发现了它们的产额和激发函数的新特征，并根据核理论对其进行了检验。用于惰性气体同位素研究的高灵敏度质谱仪已经建成并投入使用。陨石样品为Allende和Murchison，10-20克碎片分别用冻融法分解，如果是20克Allende，则根据大小和密度将其分成70个组分。然后分析了这些馏分的主量元素、微量元素和矿物组成及其赋存状态特征。本工作中发现的一些新类型的矿物赋存状态，以及分离出的馏分中稀有气体同位素的进一步分析，有望为太阳系化学元素的起源和形成历史提供观测线索。较少

1. Nucleosynthetic origin of meteoritic noble gas isotopes of anomalous isotopic compositions were further examined in light of a stellar model prediction by Heymann et al. Our three-isotope analysis has revealed the s- and r-process isotopes more distinctively than previous ones, and shown that the nucleosynthetic model is very promissing in explanation of the observed anomalies in the noble gas abundance. Stellar condition for photodisintegration was found to be the same as deduced earlier by us, i.e. the duration of the silicon burning at peak temperature of T_9=2.05 is (6.5 0.5) x 10^4 sec to yield (^<124>Xe. ^<126>Xe)_p=2.1 0.2 and the observed heavy Xe ratios to constrain the condition of the explosive phase to have a neutron dose of 3.8 x 10^<-7> [mole/cm^3.sec] yielding (^<134>Xe/^<136>Xe)_r=0.675. The carrier phase(s) for s- and r-(＆ p-) isotopes have recently been assigned to very minute SiC and diamond, respectively, but still under debate (see 3. below).2. Energetic photons … More , together with high flux of neutrons, seem to be responsible for reprocessing of chemical elements at supernova explosion. To explore this possibility, photospallation, photofragmentation, photofission and photopion reaction were studied systematically for 13 target nuclei ranging from ^<12>C to ^<209>Bi at bremsstrahlung end point energies of 30-1000 MeV. New characteristic features of their yields and excitation functions were found and examined in light of nuclear theory.3. A sophisticated mass spectrometer of high sensitivity has been constructed and under operation for noble gas isotope study. Meteorite samples were the Allende and Murchison, 10-20 g pieces of which were separately disaggregated by freeze-thaw method and separated into 70 fractions, in case of a 20 g Allende, based on size and density. These fractions were then analyzed for major and trace elements and mineral compositions and for their characteristic features of occurence. Some new types of mineral occurences found in the present work, together with further analysis of noble gas isotopes in the separated fractions, are expected to give observational clues to the origin and formation history of the chemical elements in the solar system. Less