Collective coordinates, shape transitions, and shape coexistence: A microscopic approach

We investigate a description of shape mixing and shape transitions using co llective coordinates. To that end we apply a theory of adiabatic large-ampl itude motion to a simplified nuclear shell model, where the approximate res ults can be contrasted with exact diagonalizations. We find excellent agree ment for different regimes, and contrast the results with those from a more standard calculation using a quadrupole constraint. We show that the metho d employed in this work selects diabatic (crossing) potential energy curves where these are appropriate, and discuss the implications for a microscopi c study of shape coexistence. [S0556-2813(98)04812-2].