Exotically shaped nuclei

Print edition : March 05, 2013

Researchers have found a rare example of an atomic nucleus whose shape resembles a squashed American football. Photo: Physical Review of Letters

ATOMIC nuclei can exist in a variety of shapes: depending on how the neutrons and protons arrange themselves, they can be spherical, ellipsoidal (resembling an American football) or, in rarer cases, “triaxial” (like a squashed, flattened American football). Triaxial nuclei were predicted in the 1960s and initially believed to be fairly common.

Yet, triaxial deformations have only been observed in excited states (such as those formed during nuclear reactions), in which nuclei oscillate between squashed and unsquashed shapes.

Now, a team of researchers from Japan, the United States and the United Kingdom has figured out the symmetry of an isotope of germanium (Ge) by measuring the radiation emitted by the nuclei as they were smashed into a uranium target. The results show that the atom, in its lowest energy state, is a rare, perhaps unique, example of a triaxial nucleus.