Search for two-phonon octupole vibrational bands in 88, 89, 92, 93, 94, 96Sr and 95, 96, 97, 98Zr

Several new gamma transitions were identified in Sr-94, Sr-93, Sr-92, Zr-96 and Zr-97 from the spontaneous fission of Cf-252. Excited states in Sr-88,Sr- 89,Sr- 92,Sr- 94,Sr- 96 and Zr-95,Zr- 96,Zr- 97,Zr- 98 were reanalyzed and reorganized to propose the new two-phonon octupole vibrational states and bands. The spin and parity of 6(+) are assigned to a 4034.5 keV state in Sr-94 and 3576.4 keV state in Zr-98. These states are proposed as the two-phonon octupole vibrational states along with the 6(+) states at 3483.4 keV in Zr-96, at 3786.0 keV in Sr-92 and 3604.2 keV in Sr-96. The positive parity bands in Sr-88,Sr-94,Sr-96 and Zr-96,Zr-98 are the first two-phonon octupole vibrational bands based on a 6(+) state assigned in spherical nuclei. It is thought that in Sr-94,Sr-96 and Zr-96,Zr-98 a 3(-) octupole vibrational phonon is weakly coupled to an one-phonon octupole vibrational band to make the two-phonon octupole vibrational band. Also, the high spin states of odd-A Zr-95 and Zr-97 are interpreted to be generated by the neutron 2d(5/2) hole and neutron 1g(7/2) particle, respectively, weakly coupled to one- and two-phonon octupole vibrational bands of Zr-96. The high spin states of odd-A Sr-87 are interpreted to be caused by the neutron 1g(9/2) hole weakly coupled to 3(-) and 5(-) states of Sr-88. New one- and two-POV bands in Zr-95,Zr-97 and Sr-87,Sr-89 are proposed, for the first time, in the present work.