DESSAUER, 85, ATOM BOMB PIONEER.

Byline: Wolfgang Saxon The New York Times

Dr. Gerhard Dessauer, a nuclear physicist who worked on the Manhattan Project developing the atomic bomb and at the Bikini Atoll test site before pursuing a career at E.I. du Pont de Nemours & Co., died Sunday at his home in Savannah, Ga. He was 85.

Dessauer retired in 1975 as director of the physics section of the Du Pont Savannah River Laboratory, where he dealt with theoretical and experimental physics, applied mathematics and technical information services.

He joined du Pont in 1951 after five years with General Electric Co. in Schenectady, N.Y., working on breeder reactors, reactors for submarines and experimental techniques in reactor physics.

Born in Germany, he studied chemistry at the University of Frankfurt. After coming to the United States in 1936, he earned a master's in physics at the University of California in 1939 and a Ph.D. two years later at the University of Rochester in proton-induced fission.

At Rochester, he was an associate professor and research associate when he was recruited for the Manhattan Project to research the biological effects of radiation. In 1946, he was in charge of monitoring radiation at the first postwar atom bomb tests at Bikini.

Dessauer is survived by his wife of 50 years, Marjorie Roberts Dessauer; three daughters, Leslie Dessauer of Pompano Beach, Fla., Dr. Paula Reynolds of Savannah, and Alice Dessauer of Bethesda, Md.; a son, Peter, of Harper's Ferry, W.Va.; two brothers, Ottmar, of Frankfurt, and Christopher, of Tucson, Ariz.; a sister, Maria Dessauer, also of Frankfurt; and two grandsons.