Decay Spectroscopy of Exotic Nuclei at FAIR

我们今天观察到的大部分化学元素都是从古代恒星爆炸的灰烬中产生的，这是一个令人惊讶的事实。这种类型的最壮观的事件是超新星。利用非常高灵敏度的现代望远镜，我们可以研究从遥远的超新星喷射出的物质的化学丰度，并将这些丰度与我们太阳系中发现的丰度进行比较。事实证明，了解这些丰度关键取决于核反应过程。恒星可以被认为是自然产生的核反应堆，由重力聚集在一起。对我们来说幸运的是，太阳目前还没有处于爆炸性的发展阶段。然而，现在太阳系中存在的大多数元素实际上是在早期爆炸的恒星中产生的。从这个意义上说，我们可以把自己看作是宇宙碎片。爆炸恒星的反应过程与在太阳中发现的反应过程非常不同，并且涉及到在我们的星球上从未见过的核物质。就像化学物质根据它们的电子壳层结构表现出截然不同的行为一样——钠与水反应强烈，而少了一个电子的氖是惰性气体——核物质根据它们的质子和中子的精确组成，要么非常稳定，要么非常活跃。涉及这些以前未观察到的核物质的反应是我们今天观察到的化学丰度的原因，但直到现在我们还没有机会研究它们。在德国建造的新的FAIR加速器是世界上唯一一个能够产生高强度、高能量束的加速器，这种束是最重的天然元素铀。这种元素本身是在古代超新星爆炸的一系列核反应中产生的，科学家们称之为r过程，在这个过程中，许多中子被种子核迅速吸收！我们的实验将逆转这一过程，并使用先进的分离和探测设备来观察新的外来核物质的产生

It is an astonishing fact that most of the chemical elements we observe today were created from the ashes of ancient stellar explosions. The most spectacular events of this type are supernovae. With very high sensitivity modern telescopes we can study the chemical abundances of material ejected from distant supernovae and compare these abundances with those found in our own solar system. Understanding these abundances turns out to crucially depend on nuclear reaction processes. Stars can be thought of as naturally occurring nuclear reactors held together by gravity. Fortunately for us the sun is not currently in an explosive phase of development. However, most of the elements now present in the solar system were in fact produced in earlier generations of exploding stars. In this sense, we can think of ourselves as cosmic debris. The reaction processes in exploding stars are very different to those found in the sun, and involve nuclear species never seen before on our planet. Rather like chemicals that behave very differently according to their electronic shell structure - sodium is highly reactive with water but neon with one less electron is an inert gas - nuclear species can either be very stable or very reactive according to their precise composition of protons and neutrons. Reactions involving these previously unobserved nuclear species are responsible for the chemical abundances we observe today, but until now we have had no chance to study them. The new FAIR accelerator being built in Germany is the only one in the world that can produce intense, high energy beams of the heaviest naturally occurring element, Uranium. This element itself will have been produced during ancient supernova explosions in a chain of nuclear reactions scientists call the r-process in which many neutrons are rapidly absorbed by a seed nucleus! Our experiments will reverse this process, and use advanced separation and detector equipment to observe new exotic nuclear species produced