Experimental observation of excitation and deexcitation of an as-yet unknown isomer during the irradiation of the Hf isomer by low energy bremsstrahlung photons
V.I. Kirischuk (Institute for Nuclear Research, Nauky Av, 47, Kyiv 03680, Ukraine)
•The complete set of spectra acquired during the $^{178m2}$Hf isomer triggering experiments in 2015 was reanalyzed in detail.•It looks that an as-yet unknown isomer of $^{178}$Hf is excited during irradiations.•The half-life of this isomer is expected to be between one and five days.•As a result, the efficiency of triggering, which was recorded in 2015, seems to be underestimated at least by a factor of two.•Now it seems to be clear why other experimental groups have not been able to confirm the possibility of $^{178m2}$Hf isomer triggering.
