Number 107 (Story #1), December 18, 1992 by Phillip F. Schewe and Ben Stein OUT-OF-PLANE ATOMS PARTICIPATE IN SUPERCONDUCTIVITY in yttrium-barium-copper-oxide-based materials. Researchers previously thought that if the vibrational (phonon) modes of atoms played any part in the mechanism responsible for high-temperature superconductivity, they would occur exclusively in the two-dimensional copper-oxide planes in these layered materials. Janice Nickel and Donald Morris of Morris Research, Inc. (510-704-1012) and Joel Ager of LBL have demonstrated the influence of out-of-plane atoms by studying the "isotope shift," the shift in the critical temperature which takes place when the common elements in the superconductor are replaced by their less-common isotopes. The researchers found a 0.10-0.14 K increase in the critical temperature when they replaced the naturally abundant oxygen-16 with oxygen-18 in the copper-oxide plane sites (but not elsewhere), in contrast to the 0.20 K-0.23 K overall decrease that occurs when the oxygen-18 isotope replaces the oxygen-16 at all sites. (Physical Review Letters, 14 Dec.)