Induced acceleration of the decay of the 31-yr isomer of 178m2 Hf using bremsstrahlung radiation

Abstract

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.

High-K isomers: some of the questions

“…However, much lower cross-section limits were later set [25,26]. Now there are again positive results reported [27], but this time at the lower cross-section values. This remains a controversial area of work.…”

Experimental searches for rare alpha and beta decays

“…In this and subsequent experiments, the Collins' group observed an increase of the intensities of different γ peaks emitted in the 178m2 Hf decay by 2 − 6%; the effect was seen for the 213, 217, 426, 495 keV γ peaks, and also new peaks at 130 and 2457 keV of unknown origin were detected. However, (1) in different measurements different peaks were enhanced, (2) other groups did not observe the effect, (3) the experimental results of Collins et al contradicted the theoretical estimations by orders of magnitude (see reviews [124,126,127] and one of the last works [128] and Refs. therein).…”

100 years of nuclear isomers—then and now

“…If an efficient way could be found to release that energy in a controlled manner, then a type of nuclear 'battery' could be constructed. One option would be for the energy release to be induced by externally applied radiation, and in this respect much attention has been given to the K π =9 − , T 1/2 >4.5×10 16 years isomer of 180 Ta [41,155,156], and the K π =16 + , T 1/2 =31 years isomer of 178 Hf [157][158][159]. This kind of challenge is, of course, open to all isomer types.…”