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Induced triggering Electromagnetic transitionsBremsstrahlung radiation 178m2 Hf 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 178m2 Hf 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 − -state band (with the energies of 216, 495 and 574 keV) transitions from the 178m2 Hf isomer decay were observed. Our data are consistent with the total triggering effect of 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 178m2 Hf isomer triggering.

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We analyzed possibilities for the production of 178m2Hf isomers in amounts necessary for the preparation of experimental targets. In our case the 178m2Hf isomers were produced during irradiation of the Ta converter by 1.2 GeV electrons at the Kharkiv linear accelerator many years ago. At such high electron energies the concurrent nuclear reactions are very numerous and, though all short-lived nuclei decay completely, the target is contaminated by the significant amount of long-lived nuclides. This allowed us to study the production of not only the 178m2Hf isomer, but also those of 60Co, 101Rh, 102mRh, 108mAg, 133Ba, 150Eu, 152Eu, 154Eu, 158Tb, 173Lu, 174Lu, 172Hf and 179Ta. The production yields and cross-sections for corresponding photonuclear reactions were estimated and compared with the results of other authors and calculations with the aid of the Rudstam formula.

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