Thermonuclear Fusion in the Sun and Other Stars The Sun radiates energy at the rate of 3.9 X 1026 Wand has been doing so for several billion years. Where does all this energy come from? Chemical burning is ruled out; if the Sun had been made of coal and oxygen-in the right proportions for combustion-it would have lasted for […]
Thermonuclear Fusion The Basic process The binding energy curve of shows that energy can be released if two light nuclei combine to form a single larger ucleus, a process called nuclear fusion. That process is hindered by the Coulomb repulsion that acts to prevent the two positively charged particles from getting close enough to be within range of […]
A Natural Nuclear Reactor On December 2, 1942, when their reactor first became operational (Enrico Fermi and his associates had every right to assume that they had put into operation the first fission reactor that had ever existed on this planet. About 30 years later it was discovered that. if they did in fact think that, […]
The Nuclear Reactor For large-scale energy release due to fission, one fission event must trigger others, so that the process spreads throughout the nuclear fuel like flame through a log. The fact that more neutrons are produced in fission than are consumed raises the possibility of just such a chain reaction, with each that is produced […]
The Independent Particle Model In the collective model, we assume that the nucleons move around at random and bump into each other frequently. ‘The independent particle model, however, is based on just the opposite assumption-namely, that each nucleon remains in a well defined quantum state within the nucleus and hardly makes any collisions at all! Thenucleus, unlike […]
Radioactivity and the Nuclidic Chart We can increase the information of the nuclidic chart of -4 by plotting the mass excess of each nuclide in a direction perpendicular to the N-Z plane. The mass excess of a nuclide is (in spite of its name) an energy that approximates the nuclide’s total binding energy. It is defined as […]
Beta Decay A nucleus that decays spontaneously by emitting an electron or a positron (a positively charged particle with the mass of an electron) is said to undergo beta decay. Like alpha decay, this is a spontaneous process, with a def nite disintegration energy and half-life. Again like alpha decay, beta decay is a statistical process, governedby […]
Alpha Decay When a nucleus undergoes alpha decay, it transforms to a ‘different nuclide by emitting an alpha particle (a helium nucleus, 4He). For example, when uranium 238U undergoes alpha decay, it transforms to thorium This alpha decay of 238U can occur spontaneously (without an external source of energy) because the total mass of the decay products 234Th […]
Radioactive Decay Most of the nuclides that have been identified are radioactive. A radioactive nuclide spontaneously emits a particle, transforming itself in the process into a different nuclide. occupying a different square on the nuclidic hart. Radioactive decay provided the first evidence that the laws that govern the subito ic world are statistical. Consider, for example. a I […]
Discovering the Nucleus In the first years of the twentieth century not much was known about the structure f atoms beyond the fact that they contain electrons. The electron had been discovered (by J. J. Thomson) in 1897, and its mass was unknown in those early days. Thus, it was not possible even to say how […]