Induced acceleration of the decay of the 31-yr isomer of 178m2Hf using bremsstrahlung radiation

• Upgraded experimental setup and the strongest 178m2Hf isomeric source were used.
• Triggering of 178m2Hf isomer embedded in Ta matrix by 30 keV electrons was observed.
• γ213, γ  325, γ426 keVγ426 keV GSB and γ216, γ  495, γ574 keVγ574 keV8−8− band transitions were enhanced.
• Our data are consistent with an estimate for the triggering effect of 1.55±0.12%1.55±0.12%.
• Photon induced triggering cross-section is close to the upper limit obtained earlier.

178m2Hf isomer triggering was studied using the new experimental setup developed at the Kharkiv National University and installed at the Kyiv Institute for Nuclear Research. The target presenting a single Ta foil of 300 μm thickness with the 178m2Hf isomer activity of 100 Bq was irradiated by 30 keV electron beam. The enhanced counting rates of all strongest ground-state band (with the energies of 213, 325 and 426 keV) and 8−8−-state band (with the energies of 216, 495 and 574 keV) transitions from the 178m2Hf isomer decay were observed. Our data are consistent with the total triggering effect of 1.55±0.12%1.55±0.12%. An estimate for the photon induced triggering cross-section gives a value which is close to the upper limit obtained in the earlier published works on the 178m2Hf isomer triggering.