  The oblate-prolate shape coexisting/mixing phenomena in proton-rich
68,70,72Se are investigated by means of the adiabatic self-consistent
collective coordinate (ASCC) method. The one-dimensional collective path and
the collective Hamiltonian describing the large-amplitude shape vibration are
derived in a fully microscopic way. The excitation spectra, B(E2) and
spectroscopic quadrupole moments are calculated by requantizing the collective
Hamiltonian and solving the collective Schroedinger equation. The basic
properties of the coexisting two rotational bands in low-lying states of these
nuclei are well reproduced. It is found that the oblate-prolate shape mixing
becomes weak as the rotational angular momentum increases. We point out that
the rotational energy plays a crucial role in causing the localization of the
collective wave function in the (beta,gamma) deformation space.
