‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

   On Sunday, December 6, 2020 11:06 PM, jim bell <jdb10987@yahoo.com>
   wrote:

   ...

   Ever since 2008, I have been considering isotopes, and how to use them
   to improve processes and devices. It's been a lonely task, because
   virtually every chemist or physicist views "isotopes" as merely atoms
   with a different number of neutrons, and thus a different atomic
   weight. Yes, they are indeed that, but they are so much more.
   ...

   I've long been aware that elemental (stable) magnesium isn't merely
   "magnesium".  Magnesium in nature consists of 78.99% Mg-24 isotope,
   11.01% Mg-26, and 10.00%
   Mg-25.  https://www.webelements.com/magnesium/isotopes.html

    Moreover, I was well aware that it was only the Mg-25 isotope whose
   nucleus posses 'nuclear spin': Mg-24 and Mg-26 have both an even number
   of protons, and an even number of neutrons. But Mg-25 is different: its
   nucleus contains an odd (not even) number of neutrons, and so it has a
   slight 'wobble'. The unpaired neutron can be thought as orbiting around
   the positively-charged rest of the nucleus, so that rest of the nucleus
   behaves like a positive electric charge, itself spinning around the
   center-of-mass of the whole structure. And as every physicist should
   know (my degree is in Chemistry, from MIT), a charge travelling in a
   circle causes a magnetic dipole to exist.

   From reading Mehta's description, I concluded that the problem is that
   not all of the magnesium 'worked'. I'll let you guess which one did. It
   seems fairly obvious to me.

   Zinc, similarly, is made up of
   isotopes. https://www.webelements.com/zinc/isotopes.html  Only 4.1% of
   natural, stable zinc is Zn-67 and it has a nuclear 'spin'. The rest is
   Zn-64, Zn-66, Zn-68, and Zn-70, and none of them have nuclear
   'spin'.  And I notice that some early work on GaN LEDs used Zinc as a
   p+ dopant.  It worked, I suppose, but somehow it was abandoned early
   on, since magnesium worked better. Why? Could that be because 10% is
   greater than 4.1% ? Well, THAT can be fixed!

   Doing some more research, I also notice that the radius of gallium
   atoms is 130
   picometers.  https://www.webelements.com/gallium/index.html  The radius
   of zinc atoms is 135
   picometers.  https://www.webelements.com/zinc/  And the radius of
   magnesium atoms is 150
   picometers.  https://www.webelements.com/magnesium/   So I can
   certainly understand the difficulty they had packing a 150
   picometer-radius magnesium atom into a position for suitable for a 130
   picometer gallium atom. They must have used a shoe-horn to pack the
   magnesium into the spot! Zinc's 135 picometers looks far more easily
   matched!

   Merry Christmas.  And you're welcome!

   Jim, it would be interesting to focus on isotope separation techniques.
   i get the impression that lack of affordable options precludes the use
   of enriched elements in most manufacturing.

   have you given this aspect consideration?

   best regards,