In reply to Eric Walker's message of Wed, 9 Dec 2015 16:06:32 -0600: Hi, [snip] >In oblong nuclei, there is an angular dependency on the alpha tunneling >probability. Alpha particles are more likely to tunnel out of poles of such >nuclei rather than at the circumference. Krane writes, "Since many >alpha-emitting nuclei are deformed, these angular distribution measurements >can also help us to answer another question: if we assume a stable prolate >(elongated) nucleus, will more alpha's be emitted from the poles or from the >equator? Figure 8.9 suggests a possible answer to this question: at the >larger radius of the poles, the alpha particle feels a weaker Coulomb >potential and therefore must penetrate a thinner and lower barrier." >I read this to mean that Krane believes that it is the Coulomb potential and >not the nuclear potential that is thinner and therefore easier to traverse at >the poles. Do you disagree?
1) I'm curious as to how they know that tunneling from the poles is more likely, given that they can't actually see what's going on. (Perhaps the anisotropy shows up in experiments done in a strong magnetic field?) 2) If the nucleus is oblong because it is spinning, then particles at the poles will be subject to a stronger centrifugal force. 3) Note that he only suggests the barrier is thinner as a *possible* explanation, implying possibly that no one knows for sure. 4) A positively charged particle at a pole will feel the repulsive force of *all* the other positively charged nucleons in the nucleus, pushing in the same direction. A particle at the equator, will feel approximately equal numbers of particles pushing from the one pole as from the other, so the repulsive forces tend to counteract one another. At the equator there will be some component of the repulsive forces that is perpendicular to the long axis, i.e. pointing out of the equator, but that will be small compared to the absolute magnitude of the force. (sine of a small angle). 5) In short, I doubt the validity of the proffered explanation. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
