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Chien-Shiung Wu, Renowned Columbia Physicist, 84

Chien-Shiung Wu, the renowned Columbia physicist who turned the discipline on its head by disproving the law of conservation of parity, showing that the laws of nature are not always symmetrical with respect to right and left, died Sunday afternoon (Feb. 16) in Manhattan. She was 84 years old.

She collapsed at noon and was taken by ambulance to St. Luke's-Roosevelt Hospital Center, where she was pronounced dead, said her husband, Luke C.L. Yuan, a retired experimental physicist at Brookhaven National Laboratory on Long Island. She had suffered a stroke almost two years ago and suffered another on Sunday, Dr. Yuan said.

"C.S. Wu was one of the giants of physics. In the field of beta decay, she had no equal," said Tsung-Dao Lee, University Professor at Columbia.

"She was the world's distinguished woman physicist of her time," said William Havens, professor emeritus of applied physics and nuclear engineering at Columbia.

Polykarp Kusch, one of Columbia's physics Nobelists, once said: "Her experiments have been designed with great elegance and have, by virtue of their elegance, a high esthetic quality."

She was born in Shanghai and grew up in Liuhe in Jiangsu province north of the city. She received the bachelor of science from National Central University in Nanking in 1934 and came to the United States in 1936. She studied with E.O. Lawrence, Nobelist and inventor of the cyclotron, at the University of California, Berkeley, where she received the doctorate in physics in 1940. Professor Wu taught at Smith and Princeton from 1942 to 1944.

She joined the research staff at Columbia in 1944 as a senior scientist and began work in the Manhattan Project at the Nash Building rented by Columbia at West 133rd St. and Broadway, Professor Havens said. There, Columbia scientists used diffusion techniques to separate the fissionable isotope of uranium, U-235, from the more common uranium-238. Professor Wu, Professor Havens and James Rainwater, working in the instrumentation group, used ionization chambers and Geiger counters to monitor the process.

She is best known, however, for her 1956 experiment that disproved the conservation of parity and won the Nobel Prize the following year for the two theoretical physicists who had first doubted it, Professor Lee of Columbia and Chen Ning Yang, who is now at the State University of New York at Stony Brook.

She conducted the experiment at the National Bureau of Standards in Washington, D.C., which provided a cryogenics laboratory where the necessary low temperatures could be maintained. The basis for the experiment was a salt of radioactive cobalt-60 and her considerable expertise in beta decay, or the emission of electrons from radioactive nuclei. Her method was to place the cobalt in a strong magnetic field to line up the north-south magnetic poles of its nuclei, supercool it to minimize the atoms' random thermal motions, and then watch where the electrons it emitted went.

She found that a majority of the tens of thousands of electrons emitted by the cobalt every second were ejected primarily in one direction. The discovery stunned scientists, for it showed that the laws of nature are not always symmetrical with respect to right and left.

Within days, Leon Lederman and Richard Garwin, then young physicists at Columbia, conducted experiments at the University's Nevis Cyclotron and confirmed the result. Physicists came to realize that parity nonconservation was the basic property of a single force, now called the weak interaction, one of the four basic forces of the universe.

At Columbia, she was named associate professor in 1952, full professor in 1958 and the first Pupin Professor of Physics in 1973. She retired in 1980. Her book, Beta Decay, remains the standard reference on low-energy emission of electrons by decaying atoms. Later in her career, she conducted research into molecular changes in hemoglobin associated with sickle-cell anemia.

Among her many honors and awards were the Research Corporation Award in 1958, the Industrial Research Scientist of the Year in 1974, the National Medal of Science in 1975, the first Wolf Prize in Physics in 1978 and Columbia's Pupin Medal in 1991. She was elected to the National Academy of Sciences in 1958, the Royal Society of Edinburgh in 1969 and the American Academy of Arts and Sciences in 1972. In 1973, she was chosen the first woman to head the American Physical Society. Professor Wu received numerous honorary degrees from universities in the United States and abroad.

Dr. Yuan and Professor Wu met at Berkeley and were married in 1942. They had resided in the same Claremont Avenue apartment near Columbia's Morningside Heights campus for more than 50 years.

In addition to her husband, Professor Wu is survived by her son, Vincent Yuan, of Albuquerque, N.M., who earned the bachelors degree in 1967 and a doctorate in physics in 1977, both from Columbia. He is a research scientist at Los Alamos National Laboratory.