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The previously unreported decay of '~Sr to levels in '0 Y has been studied from mass-separated activity produced in the thermal neutron fission of 'U. -A half-life for '0 Sr was measured to be 68+8 ms. Based on y singles and coincidence measurements, 24 y rays were placed in a level scheme for ' Y with nine excited states up to 1689 keV. Four excited states were assigned a J af 1+ from logft values. Evidence for delayed-neutron emission from 'OtSr is reported. These results are compared with systematics for other neighboring, highly deformed, odd-odd Y and Nb nuclei.The level structure of A -100 Y nuclei, which exhibit a very abrupt transition from spherical to highly deformed shapes, is reviewed. The possibility of the existence of bands with moments of inertia close to that of a rigid rotor is discussed.

The level structure of the %=60 isotone '~Zr has been studied via the decay of the low-spin isomer of ' Y. A half-life of 735+7 ms was determined from y-ray multiscaling measurements. y singles and y-y coincidence measurements have resulted in the placement of 64 y transitions in a decay scheme with 20 levels up to 4288 keV. Angular correlation measurements were used to deduce a J of 0+ for the 829-keV level. A simple band-mixing calculation is presented which supports a picture of the structure of the low-lying levels in '~Zr as that of coexistence between an axially symmetric deformed yrast band and a nearly spherical excited band.

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