| MadSci Network: Physics |
There are different ways to 'tweak' nuclei into decaying. All of them involve the nuclei absorbing a particle or colliding with another nuclei. The most commonly used process is by bombarding it with slow neutrons. The nuclei would absorb the neutron and either break apart immediately or decay at a different rate than the mother nucleus. What happens depends on the nuclei and the energy of the neutron. As an example, U-238 in a nuclear reactor would capture a slow neutron and turn into U-239. U-239 decays about 10^20 times faster than U-238 and releases energy and 2-3 more neutrons, leading to a chain reaction. Another way to make even a stable nuclei 'decay' is by letting it absorb a negatively charged pion. A pion contains an anti-quark, which annihilates with a quark in the nuclei and shatters the nuclei into several fragments. This effect is observed in bubble chambers at the end of the track of a pion when the pion slows down sufficiently to be captured. The track appears to terminate in a "star" of tracks, which corresponds to nuclear fragments. A wonderful example is given in : D.H. Perkins, Nature: January 25, 1947: Vol 159, p. 39. One of my colleagues mentioned that work was done at Berkeley to study the effects of chemistry on nuclear decays. Some nuclei decay via electron capture, where an orbital electron of the atom is captured by the nucleus. The electron "combines" with an proton and creates a neutron and neutrino, hence generating a nucleus with one less proton and one more neutron. The rate for this process is determined by the electron's wavefunction, which can be altered by chemical bonds. I have not been able to find any references for this, but it sounds very plausible to me. The effect would be small, though. During accelerator runs the energies are usually very high and shatter the nuclei. You will not be able to do gentle 'tweaking' experiments. There are several excellent text available on nuclear physics. An elementary overview is given in: Eisberg and Resnick's "Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles" A more advanced text that I like is Samuel S.M. Wongs "Introductory Nuclear Physics". A good reference for information on nuclear properties is http://isotopes.lbl.gov/isotopes/ip.html A searchable website that contains most of the physics papers published in major american journals over the last 10 years is at http://xxx.lanl.gov/ You should be able to find a lot of nuclear physics papers there Hope this helps, Reyco Henning
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