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1、Radiochemistry 放射化学 Chapter1 Origin of Nuclear Science 第一章 核科学起源Wilhelm Conrad Roentgen (1845-1923) In 1895 W. Roentgen 伦琴 discovered that when cathode rays 阴极射线(i.e. electrons) struck the wall of an evacuated glass tube, it caused the wall material to emit visible light (fluoresce荧光), while at the
2、same time a very penetrating radiation 穿透辐射was produced. The name X-ray was given to this radiation.发现x射线Antoine Henri Becquerel (1852-1908) Becquerel 贝克勒尔soon found that the radiation causing the blackening was not “a transformation of solar energy“ because it was found to occur even with assemblie
3、s that had not been exposed to light; the uranyl (铀酰)salt obviously produced radiation spontaneously. This radiation, which was first called uranium rays (or Becquerel rays) but later termed radioactive radiation (or simply radioactivity)1, was similar to X-rays in that it ionized air, as observed t
4、hrough the discharge of electroscopes.研究x射线产生原因时，发现 硫酸钾复盐具有的自发射线Becquerel 的发现v Roentgen（伦琴）发现了令人费解的射线，这种射线在玻璃壁和其它一些材料中会产生荧光（当时称为磷光）；v 1880年Becquerel，受他祖父和父亲的影响，对磷光现象感兴趣，制备出硫酸铀酰钾（K2UO2(SO4)2.2H2O）；v 1896年， Becquerel 提供了第一批实验结果：硫酸铀酰复盐晶体受强烈阳光照射后，放出一种穿透能力很强的辐射；（1）在强光、弱光、无光的条件下，铀盐都具有感光现象；（2）其它铀盐、亚铀盐、铀盐溶液
5、、金属铀都能产生这种辐射，且与铀含量成正比；Marie Curie (1867-1934) Marie Curie 玛丽居里 subsequently showed that all uranium and thorium compounds produced ionizing radiation independent of the chemical composition of the salts. This was convincing evidence that the radiation was a property of the element uranium or thorium
6、. Moreover, she observed that some uranium minerals such as pitchblende沥青铀矿 produced more ionizing radiation than pure uranium compounds.发现U，Th也有类似的性质， 进一步研究时发现某些矿物 中的放射性比其中所含U，Th 的放射性要强的多After hard working, the Curies discovered polonium钋(1898,7)1898,9 the Curies, together with G. Bemont, isolated
7、another radioactive substance for which they suggested the name radium镭.In order to prove that polonium and radium were in fact two new elements, large amounts of pitchblende were processed, and in 1902 M. Curie announced that she had been able to isolate about 0.1 g of pure radium chloride from mor
8、e than one ton of pitchblende waste. The determination of the atomic weight of radium and the measurement of its emission spectrum provided the final proof that a new element had been isolated.Curie夫妇 的成就v发现钍发出与铀具有相似的射线；v天然铀矿石的放射性比纯铀、人工合成铀矿石的强；v在天然铀矿石的分离过程，发现了钋和镭元素，并经光谱法证实；测定了镭的分子量226.5；v建立了首个镭和钡分离的
9、化学分离方法；v测定了浓缩铀式样的热效应，发出100cal/g.h。W. Crookes and Becquerel made an important discovery. Precipitating a carbonate salt from a solution containing uranyl ions铀酰 离子, they discovered that while the uranium remained in the supernatant liquid 上层清液in the form of the soluble uranyl carbonate complex, the r
10、adioactivity originally associated with the uranium was now present in the precipitate, which contained no uranium. Moreover, the radioactivity of the precipitate slowly decreased with time, whereas the supernatant liquid showed a growth of radioactivity during the same period (Fig. 1.1).Similar res
11、ults were obtained by E. Rutherford and F. Soddy when investigating the radioactivity of thorium. Later Rutherford and F. E. Dorn found that radioactive gases (emanation射气) could be separated from salts of uranium and thorium. After separation of the gas from the salt, the radioactivity of the gas d
12、ecreased with time, while new radioactivity grew in the salt in a manner similar to that shown in Fig. 1.1. The rate of increase with time of the radioactivity in the salt was found to be completely independent of chemical processes, temperature, etc. Rutherford and Soddy concluded from these observ
13、ations that radioactivity was due to changes within the atoms themselves. They proposed that, when radioactive decay occurred, the atoms of the original elements (e.g. of U or of Th) were transformed into atoms of new elements.Rutherford和Soddy的转化假说v 1899年发现在钍、镭和锕的化合物都可以释放出放射性的射气，这种射气是惰性的。v 在射气的研究中，得
14、到两个重要的结论：（1）放射性物质的放射性活度不是永远不变的，是随时间而衰减的，其时间特性因物质而异；（2）放射性过程伴随有放射性原子的化学性质而变化。v 1903年， Rutherford和Soddy才对放射性的本质有十分深入的了解：v （1）放射性元素不断地自发地从一种化学元素转变为另一种元素；v （2）上述转化过程中伴随着放射性辐射；v （3）这种放射性过程是原子内部的亚原子变化。The radioactive elements were called radioelements. Lacking names for these radioelements, letters such a
15、s X, Y, Z, A, B, etc., were added to the symbol for the primary (i.e. parent) element. Thus, UX was produced from the radioactive decay of uranium, ThX from that of thorium, etc. These new radioelements (UX, ThX, etc.) had chemical properties that were different from the original elements, and could
16、 be separated from them through chemical processes such as precipitation沉淀, volatilization挥发, electrolytic deposition电解沉积, etc. The radioactive daughter elements decayed further to form still other elements, symbolized as UY, ThA, etc.A careful study of the radiation emitted from these radioactive elements demonstrated that it consisted of three components which were given the designation alpha (), beta (), and gamma(). Alpha-radi
