[理学]ch2核合成.ppt

charged-particle induced reaction mainly neutron capture reaction during quiescent stages of stellar evolution involve mainly STABLE NUCLEI mainly during explosive stages of stellar evolution involve mainly UNSTABLE NUCLEI nuclear processes the s-process Fe Co Ni Rb Ga Ge Zn Cu Se Br As Zr Y Sr Kr (n,g) (b-) (b+) r-process p-process 63Ni, t1/2=100 y 64Cu, t1/2=12 h, 40% (b-), 60% (b+) 79Se, t1/2=65 ky 80Br, t1/2=17 min, 92% (b-), 8% (b+) 85Kr, t1/2=11 y r-only p-only s-only neutron number proton number (from Rene Reifarth) 核合成 小结 自然界的核素从何而来? 氢-1(质子)来自大爆炸， 氦-4来自大爆炸与恒星核燃烧， 比铁-56轻的核素来自恒星核燃烧， 比铁-56重的核素主要来自中子俘获。 2. 太阳的命运是什么? 50亿年以后，太阳将燃烧完其中的氢，成为红巨星。 3. 核合成的“指纹”在哪里？ r-only: 30Zn40 p-only: 34Se40, 36Kr42 s-only: 38Sr48 * Kirchoff定理 * * * Resolution of these profound questions could unlock the secrets of existence and deliver a new age of science within several decades. by Eric Haseltine, Illustrations by Dan Winters Gary TanhauserHeres a tale of modern physics: Two scientists work at the same university in different fields. One studies huge objects far from Earth. The other is fascinated by the tiny stuff right in front of him. To satisfy their curiosities, one builds the worlds most powerful telescope, and the other builds the worlds best microscope. As they focus their instruments on ever more distant and ever more minuscule objects, they begin to observe structures and behaviors never before seen—or imagined. They are excited but frustrated because their observations dont fit existing theories. One day they leave their instruments for a caffeine break and happen to meet in the faculty lounge, where they begin to commiserate about what to make of their observations. Suddenly it becomes clear to both of them that although they seem to be looking at opposite ends of the universe, they are seeing the same phenomena. Like blind men groping a beast, one scientist has grasped its thrashing tail and the other its chomping snout. Comparing notes, they realize its the sa