Hafnium controversy

Peter Zimmerman (an American nuclear physicist and arms-control expert) described claims of weaponization potential as having been based on "very bad science".

[3] 178m2Hf is a particularly interesting candidate for induced gamma emission (IGE) experiments, because 178m2Hf's energy is 2.5 MeV per nucleus higher than that of ground-state Hf, and it has a long 31-year half life.

The long half life of 178m2Hf might make it possible to engineer a substance with enough of these energetic nuclei needed for stimulated emission, i.e. a gamma-ray laser.

A proposal to show the efficacy for "triggering" 178m2Hf was approved by a NATO Advanced Research Workshop (NATO-ARW) held in Predeal in 1995.

A controversy quickly erupted, mostly between the original proponents of 178m2Hf as having potential military applications as a gamma-ray laser weapon or a non-neutronic but still nuclear-like explosive, and critics who discounted such possibilities due to practical obstacles along the way: 178m2Hf is difficult to make and virtually impossible to separate from the ground-state Hf, the absorption of lower-energy triggering x-rays by the bound electrons around the Hf nucleus, and the minute probability to recreate the trigger-capable x-ray starting with the triggered x-ray itself by multiple random scattering.

Experiment producing IGE from a sample of the nuclear isomer 178m2 Hf. (left to right) Students on duty; (w/ladder) the world's most stable beamline for monochromatic X-rays, BL01B1; (rt.) main ring of the SPring-8 synchrotron at Hyogo.