quote:

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...its nuclear reactor is unlike any other. Rather than split heavy elements or fuse light atoms--as in fission and fusion reactors--it will use what is known as a triggered isomer reaction. If this new powerplant, called a quantum nucleonic reactor, performs as scientists expect, its effect on the aircraft industry may prove as revolutionary as the introduction of the jet engine.

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There is some dispute in the literature as to whether or not the triggered isomer transition and the "re-energization" of Hafnium-178 is (a) actually possible and (b) if possible, there are doubts as to feasibility. (The one for Tantalum is known to happen, but there may be nuclear-structure reasons for this and there is no guarantee that the shell structure for Tantalum versus Hafnium is similar enough to warrant making the claim of triggered Hafnium isomer decays before full investigation)

One of the cited reasons for doubting the triggered-decay claim is that the orbital electrons will tend to absorb a roughly 40 keV X-ray burst, so that the likely result of such will simply be Auger electrons or resonant X-rays. The transition probability is not zero for transferring that X-ray energy to the nucleus, but it is on the order of 1 in 1000. This would, presumably, lower the effective cross-section and render the matter of theoretical use only.

A somewhat technical article on the Hafnium Controversy

[ 10 October 2004: Message edited by: DrConway ]

Anyway, since nucleons are fermions, just as electrons are, there are strongly analogous properties, such as the presence of discrete energy levels, and the ability to do single-particle excitations from ground-state to excited-state configurations.

However, one key difference in the quantum mechanics involved is that first of all, the discrete-energy-level model (the "shell model") has to take into account the strong interaction, so that so-called spin multiplicity is not preferred for nucleons. Additionally, spin-orbit coupling is very strong in the shell model, so the energy levels become more complicated to deal with. Then you have to throw into the mix the experimentally established existence of nuclear dipole and quadrupole moments, which implies distortion of nuclei away from spherical shapes, which means the shell model becomes less useful in certain regions of the chart of isotopes, further requiring resort to so-called "Nilsson levels" and/or the "collective model", which is used to explain why rotational effects are seen in nuclei.

As far as spectroscopy goes, one major difference is that nuclear rotational/vibrational/single-particle-type excitations all overlap in energy and are often hard to distinguish when sorting out gamma-ray cascades, as opposed to atomic/molecular electron excitaions, molecular vibrations and molecular rotations which all have characteristic energies which are distinct from each other.

Atomic/molecular excitations are usually in the visible-light or X-ray region, while vibrations are in the infrared and rotations in the microwave region.

You can see one of the major reasons why chemical spectroscopy is a lot easier to understand and handle than nuclear spectroscopy.

I could go on for quite some time, but I'll stop here.