“…Consequently despite the fact that the first 3 − state of 208 Pb has a large quadrupole moment, which indicates a significant anharmonic effect in octupole vibrations [33,34,35,36], a direct study of the anharmonic properties in multi-octupole phonon spectra has not been possible for a long time. Only in recent years, convincing evidence have been reported for doubleoctupole-phonon states, as well as double-phonon states built from single octupole and quadrupole phonon states, in some nuclei, e.g., 208 Pb [37], 144 Sm [38,39,40,41 [43], and 148 Gd [44,45].…”