VIBRATIONAL STATES OF NUCLEI

Aage Bohr and Ben Mottelson
(Nobel Prize, 1975.)

This is NOT what the nucleus is doing!



Studies of the reduced electromagnetic transition probability B(E2) reveal that indeed these states have a transition strength equivalent to that of many, many single particles. They are indeed “collective” states.


One of the most important developments in understanding the collective states of nuclei was the discovery of the Giant Dipole Resonance; it is usually excited by an energetic photon. Since the discovery of this collective 1- state, many other giant resonances of many different types have been found. The most recent discovery, of a new kind of monopole spin-isospin excitation, was just a few years ago.




Monopole isovector spin resonance!

There has been great interest in the monopole resonances, since they can involve nuclear compression of one kind or another, and thus give an insight into the nuclear equation of state that is difficult to obtain otherwise.


The more physics you know, the more surprising it might be that there are quite a few nuclei that exhibit a permanent deformation, breaking what one would expect to be a required symmetry under all rotations, for any system possessing a definite angular momentum quantum number! Well, that sounds like a job for the ever-useful concept of broken symmetry. In fact the rotational states can be considered the Goldstone Bosons that have to exist BECAUSE of the broken symmetry. However, the needed math is quite difficult and confusing, and gets about as ugly as the math of molecular vibrational/rotational spectra, especially because nuclei too exhibit vibrations built on rotations, etc.








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