Re: [Vo]:Re: HUP-spread-out electron "feels" (and thus Coulomb-screens?) like a point charge... - T.GIF

[Robin van Spaandonk]

In reply to  Michel Jullian's message of Mon, 28 Apr 2008 01:33:07 +0200:
Hi,
>Robin,
>
>Although it seems to make sense, something doesn't fit in your center of mass 
>frame of reference and therefore equal De Broglie wavelengths (DBW) paradigm: 
>in that frame, as you say, "when the particles are stationary relative to one 
>another, the DBW is infinite, hence no longer relevant", whereas that distance 
>r1 where the incident d has lost all its initial kinetic energy is precisely 
>where the Li et al paper compares the distance by which it "missed" (r1-r0) 
>with the DBW, which they don't find infinite but equal to 0.78 Å...
>
>But on the other hand, how can the DBW not be infinite if momentum is zero??

Without re-reading their paper, I think you will find that the DBW they
calculate is based upon thermal energy. That's fine for a first rough guess,
which is why I said it's a rule of thumb. What they mean is that the DBW is *at
least* that big, ergo tunneling is possible. It's also possible that they are
simply guilty of sloppy thinking.

>
>On yet another hand, the DBW seems the right parameter to define the "spread" 
>of a particle and therefore its capacity to tunnel or be tunneled to... if 
>it's infinite, it's all over the place so tunneling should have 100% 
>probability!

No, just possible, not necessarily probable. It's only infinite for a very short
period of time. Probability is also determined by confinement time, and at least
in the literature, by the cross section of the nuclear reaction. (However IMO,
QM probably compounds tunneling probability with the cross section). IOW while I
have tried to separate the two, QM usually doesn't.

>
>This point is definitely unclear to me, any enlightening welcome.
[snip]
Regards,

Robin van Spaandonk

The shrub is a plant.