Number 35 (Story #4), May 22, 1991 by Phillip F. Schewe and Ben Stein BAND TWINNING is the name for a curious similarity in the energy spectra of certain superdeformed nuclei, nuclei that are oblate or stretched out and quickly rotating as a result of high-energy collisions. Marie-Anne Deleplanque of LBL (415-486-5384) reported at last month's APS meeting in Washington, D.C. that the sequence (or band) of gamma rays emitted by superdeformed dysprosium-152 and terbium-151 are surprisingly like the pattern observed for nuclei (such as mercury) in the atomic mass range of 190. According to Deleplanque, "There is no explanation for any of these properties based on our present knowledge of nuclear structure." (Science 10 May.)