Physicists normally think of atomic nuclei as being something like
a droplet with a roughly spherical shape. But if atoms can assemble
into tiny pyramid structures (such as the ammonia molecule, NH4),
why not nuclei? It all depends on how the nuclear forces act in a nucleus.
A group of physicists from the Universite Louis Pasteur (Strasbourg,
France) and the Marie Curie University (Lublin, Poland) have, for the
first time, tried to imagine how stable nuclei could form with pyramid,
or even cubic or octahedral shapes.
In chemistry many configurations are possible because the interactions
(e.g., Van der Waals, covalent, or hydrogen bonding) can extend over
The nuclear force, by contrast, is attenuated, and acts not much further
than the size of nucleons (the protons and neutrons making up the nucleus).
An excited pyramidal nucleus would turn in space, every now and then
throwing out a high-energy photon (gamma ray). This would make for a
characteristic spectrum, but one which would most likely require a gamma
detection sensitivity only now being planned for experiments in the
US and Europe.
Jerzy Dudek (email@example.com, 33-388-10-6498) and his colleagues
have worked out the "magic numbers" for those elements and
isotopes most likely to be sustainable in tetrahedral form, nuclei with
certain numbers of protons (e.g., 20, 32, 40, 55/58, 70) and neutrons.
For example, barium-126 (56 protons, 70 neutrons) and barium-146 (56
protons, 90 neutrons) have promise, whereas Ba-114 or Ba-168 do not.
al., Physical Review Letters, 24 June 2002.)