Nuclear physics: Long live isomer research Excited quantum states in nature are normally extremely short-lived, and this certainly applies to most nuclei. But what makes the metastable nuclear states different? And how can we exploit them for useful applications?
Introduction An isomer is an excited quantum-mechanical state of a nucleus, in which a combination of nuclear structure effects inhibits its decay and endows the isomeric state with a lifetime that is longer than expected (some examples are shown in Table 1). The strong force that binds a nucleus together and the exchange of the mediators of this force lead to immeasurably short lifetimes of the order of 10 ^ -24 s for most nuclear states. But known isomers in nuclei span the entire range of lifetimes from 10 ^ 15 years for 180mTa (m = metastable) — longer than the accepted age of the universe — to an informal rule of thumb on the lower side of approximately 1 ns. This inhibition to decay leads to the storage of enormous amounts of energy in these states (10 ^ 4 or 10 ^ 5 times more than chemical energy release). The challenge and potential for scientific discovery today lie in the understanding of the formation of nuclear isomers (through a better comprehension of nuclear structure), the ability to excite and de-excite isomers at will for a broad range of applications from isomeric bombs to a clean source of energy, and the exploration of nuclei with isomeric states in nuclear astrophysics to determine how they affect the creation of the elements in the universe, and how they eventually contribute to the makeup of life in our cosmos. continues... http://www.nature.com/nphys/journal/v1/n2/full/nphys150.html
