178m2Hf

178m2Hf, hafnium-178m2, is a nuclear isomer of hafnium-178 representing a metastable excited state. It is denoted m2 to indicate the second metastable level. The isomer has an excitation energy of about 2.446 MeV above the ground state and a relatively long half-life on the order of decades, commonly cited as around 31 years. Its spin and parity are reported as Jπ = 16+, and it decays primarily by gamma emission to the ground state, with internal conversion contributing to de-excitation.

Production and isolation of 178m2Hf occur in nuclear environments where hafnium isotopes undergo neutron capture or high-energy irradiation, such as in reactors or accelerators. Samples are prepared and purified in specialized facilities for spectroscopic study, isomer characterization, and investigations into de-excitation pathways. The isomer’s properties are studied through gamma spectroscopy and nuclear transition measurements.

The isomer has attracted attention as a potential high-energy-density storage medium because its excitation energy is stored in a relatively stable metastable state. The idea of triggering controlled energy release on demand has driven experimental and theoretical work exploring various stimulation methods, including photon or X-ray exposure and other external perturbations. To date, no reliable, scalable mechanism for practical, on-demand energy release from 178m2Hf has been demonstrated, and standard radioactive decay remains the dominant end state.

In current scientific use, 178m2Hf serves as a case study in nuclear structure, isomeric transitions, and the challenges of harnessing nuclear energy in metastable states. It remains a topic of research in nuclear physics and materials science, with ongoing discussion about its feasibility for energy applications.