Number 119 (Story #3), March 19, 1993 by Phillip F. Schewe and Ben Stein THE BERRY PHASE , a phase shift acquired by quantum systems solely from topological effects, can create noticeable effects in even simple chemical reactions. Chemists once thought that reaction rates for simple exchange reactions such as H+H2H2+H could be determined from first principles. Mark Wu and Aron Kupperman of Caltech have found that theoretical calculations for the D+H2DH+H reaction fit experimental data better when they included this esoteric phase effect, named after the University of Bristol's Michael Berry, who discovered it in quantum systems in 1983. (Physics Today, March 1993.)