Search for two-phonon octupole vibrational states and multiplets in Sr and Zr nuclei

first, second and third experimental candidates of the two-POV states were a 19/2 state in Gd with the configuration of νf7/2⊗3 ⊗3 reported in 1979 [4] and 1982 [5], a 19/2 state in Gd with the configuration of ν(f7/2) 3 ⊗3⊗3 reported in 1981 [6] and a 12 state in Gd with the configuration of 6⊗3⊗3 reported in 1984 [7], respectively. The two-POV quartet of 0, 2, 4 and 6 states were proposed in Zr in 1989 [8]. Also, two-POV states were experimentally suggested for Nd [9,10] and Sm [11,9,10] and recently Gd [12]. Nine of 11 previously known cases belong to the Gd