Alexander Langsdorf Jr., a physicist who worked to develop the atomic bomb, pleaded with his Government not to use it and was heartbroken when Hiroshima and Nagasaki were laid waste, died on Friday at Elmhurst Memorial Hospital near Chicago. He was 83.
Dr. Langsdorf, who lived in the Chicago suburb of Schaumburg, died of complications after hip surgery, the family said.
Dr. Langsdorf's contribution to the Manhattan Project was just a speck -- a speck of plutonium, some of the first usable sample of the radioactive element. Dr. Langsdorf produced the speck from a cyclotron, an atomic-particle splitter, which he and another scientist had built at Washington University in St. Louis for medical research just before World War II.
The speck was used in tests in Los Alamos, N.M., before the first atomic bomb was exploded in the New Mexico desert on July 16, 1945. That bomb was plutonium-fueled, as was the one dropped on Nagasaki. (The bomb dropped on Hiroshima was a uranium-fueled device.)
Dr. Langsdorf's wife of 54 years, Martyl, recalled on Friday how her husband had expressed anguish as President Harry S. Truman and a handful of advisers deliberated amid utmost secrecy whether to use the atomic bomb to end the war. "He thought it was unbelievably inhumane to drop it on an open city and kill so many civilians," Mrs. Langsdorf said.
He felt so strongly that he became one of 70 scientists to petition Truman not to use the bomb. If the United States did, the scientists argued, it would fail its "solemn responsibility" to avert the postwar spread of nuclear weapons.
If the atomic destruction of the two Japanese cities hastened the war's end, it was at a terrible cost, Dr. Langsdorf believed. His grief ran deeper when, three decades after the war's end, he spent a year in Japan as a visiting professor and consultant at Tohoku University in Sendai.
When he and his wife were touring the country, their train stopped near the shrine at Hiroshima. The other travelers got off the train to pay homage, Mrs. Langsdorf recalled. But her husband "just sat there with tears in his eyes."
Dr. Langsdorf was one of the designers of the first two nuclear reactors that followed the first sustained nuclear chain reaction at the University of Chicago in 1942, his colleagues at the university's Argonne National Laboratory said.
He also invented the diffusion cloud chamber, a device widely used for nuclear and cosmic-ray research from the late 1940's through the 1950's. And he designed the reactor oscillator, a machine used to measure neutron cross sections.
Alexander Langsdorf was born in St. Louis on May 30, 1912, and graduated from Washington University in 1932. In 1937, he received a doctorate in physics from the Massachusetts Institute of Technology. He was a research fellow at the University of California at Berkeley in 1938 and the next year became a physics instructor at Washington University, where he remained through 1942.
After supervising the operation of the plutonium-refining cyclotron at Washington University early in the Manhattan Project, Dr. Langsdorf joined Enrico Fermi in Chicago in 1943 to do basic research in neutron physics. He remained there after the university's Argonne laboratory was formed, and he was on its staff until his retirement in 1977.
Besides physics, Dr. Langsdorf had one other passion: gardening. Mrs. Langsdorf said he had planted 20 pine trees, now 60 feet tall, around their home. He raised so many tomatoes and zucchini that his colleagues got a steady supply, as did Mrs. Langsdorf's friends in the art world. (She is a landscape painter who works under the name Martyl.)
Surviving besides his wife are two daughters, Suzanne Hasha of Arlington, Va., and Alexandra Shoemaker of Aptos, Calif., and four grandchildren.
