On Wed, Dec 9, 2015 at 8:26 PM, <mix...@bigpond.com> wrote: 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?) >
Yes -- this type of experiment requires first aligning the magnetic dipole or electric quadrupole moments of the alpha-emitting nuclei in a magnetic field or a crystalline electric field gradient. In order to keep the spins aligned they must keep the atoms below 0.01 K. 2) If the nucleus is oblong because it is spinning, then particles at the > poles > will be subject to a stronger centrifugal force. > I get the impression they were looking at deformed nuclei, whose ground states are oblong. 3) Note that he only suggests the barrier is thinner as a *possible* > explanation, implying possibly that no one knows for sure. > True. > 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). > Yes, I imagine this is possible. 5) In short, I doubt the validity of the proffered explanation. > Understood. I only wanted to get agreement on what Krane's understanding is. I think Krane's understanding is the mainstream position. This is not necessarily the correct one, but it's good to know what it is if one is going to take a position against it. Given the extreme subtleties of the experimental data in this particular field and the success of practitioners in untangling a number of details, I'm personally inclined to go with Krane's understanding as a first pass, but this doesn't mean everyone should. Eric
