Identification of high spin states and nearly degenerate $\Delta$I=1 bands in $^{100}$Zr

Eight new high spin states and twenty-three new $\gamma$ transitions have been identified in $^{100}$Zr from studies of $^{252}$Cf spontaneous fission with Gammasphere. A near-spherical excited band in $^{100}$Zr based on the 331.1 keV 0$^+$ state is extended from 4$^+$ up to 12$^+$. A $\Delta$I = 1 band with band-head energy of 2316.1 keV is extended. This band now forms $\Delta$I=1 doublet bands with the previously known $\Delta$I=1 band begining at 2259.8 keV. The energy difference between the bands with the sam spins in the two bands are nearly degenerate, $\Delta$E= 25.2(8$^+$), 8.6(9$^+$), 4.8(10$^+$) and 12.1(11$^+$) keV. Our theoretical calculations indicate the coexistence of prolate and oblate shapes for the two 0$^+$ bands in $^{100}$Zr. We propose the possible coexistence of prolate, oblate and triaxial shapes for the highly excited 2 quasiparticle bands.