Older nuclear structure models.

[carllacan]

Hi people.

I just read this somewhere

A first assumption was that nuclei were composed of A protons and Z - A electrons, so that the mass would be A·u and the charge Z·e, but this was uncompatible with Heisenberg’s Uncertainty relation (delta-p would be so big that the electron would be unbounded) and the nuclear spin of the deuteron (which was known to be I= 1·h instead of the values of ½ · h or 3/2·h this model gave)

and I can't get my head around it.

How is the Uncertainty Relation uncompatible with the idea of a proton-electron nucleus?

And can you explain why this model predicted those values for the nuclear spin?

Thank you.

 

[Bill_K]

the nuclear spin of the deuteron (which was known to be I= 1·h instead of the values of ½ · h or 3/2·h this model gave)

And can you explain why this model predicted those values for the nuclear spin?

In this model the deuteron would consist of two protons and one electron, i.e. three spin-1/2 particles. To get the resulting overall spin, you would have to combine three spin-1/2's with whatever orbital angular momentum there was. However you do it, the total spin comes out half-integer.