Phase transition in exotic nuclei along the N=Z line

The abrupt structure change from the nuclei of N=Z⩽35 to those of N=Z⩾36 is investigated by means of shell model calculations. Basic features of all even-even and odd-odd nuclei under consideration are well reproduced. A sudden jump of nucleons into the upper g9/2d5/2 shell at N=Z=36 is found to be the main reason for the cause of the qualitative structure difference. It is argued that the structure change can be viewed as a decisive change of the mean field, or a phase transition, along the N=Z line.