What is nuclear isomer energy storage and why could it matter?

The answer

Nuclear isomers are excited states of atomic nuclei that can store energy for extraordinarily long periods. Hafnium-178m2, for example, stores 2.45 MeV per nucleus - yielding energy densities roughly one million times greater than chemical batteries. The challenge is triggering controlled energy release. In the early 2000s, controversial experiments at the University of Texas claimed stimulated emission from hafnium-178m2 using X-rays, but results were not reproduced. More promising is thorium-229, which has an exceptionally low-energy nuclear isomer transition at just 8.338 eV, accessible with ultraviolet lasers. In 2024, scientists at JILA and PTB directly excited this transition for the first time, opening paths to nuclear clocks 10 times more precise than atomic clocks and potentially controllable nuclear energy storage systems.