In reply to Eric Walker's message of Wed, 9 Dec 2015 15:11:42 -0600: Hi, [snip] >On Wed, Dec 9, 2015 at 2:39 PM, <mix...@bigpond.com> wrote: > >IOW the barrier does work in two directions (due to the two forces at >> work), but >> is never named accordingly. So I suspect that it's just the naming >> convention >> that is confusing you. >> > >When calculating the tunneling probability of an alpha particle, the width >of the Coulomb barrier is an important term in the calculation. The >tunneling rate ranges from fractions of a second to billions of years as a >result of small changes in this term. The Coulomb barrier width extends far >beyond the reach of the nuclear force, which is on the order of ~ 1 fm. If >the nuclear force were the only thing keeping the alpha particle within the >potential well of the nucleus, one would expect any geometrical >considerations in the calculation to extend beyond the nucleus itself on >the order of ~ 1 fm, which is far from the case in this calculation. > >I think we went over this ground earlier, and I'm having trouble finding >your reply. Of course, you could very well be correct, and I will keep an >open mind.
Yes we did. :) When the width of the barrier is calculated, it is based upon the energy remaining to the alpha particle once it has escaped. The lower that energy, the longer is the half life. Note however that if a particle once having escaped only has a little energy left, then it apparently didn't have much to start with. If it didn't have much to start with, then it's not surprising that it found it difficult to overcome the nuclear barrier, hence the long half life. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
