Possibly abrupt transition to a new structure regime in very light Pm and Sm nuclei

A sudden transition into a region of well-deformed isotopes is predicted to occur specifically in the promethium and samarium nuclei at N approx. equal to 73. Spectroscopic signatures of the phase change are proposed for odd-mass samarium nuclei. The inherent interest in the transition and in looking for a new region of stable rotational properties is discussed. (orig.)