George Cowan addresses a Los Alamos National Laboratory colloquium in Los Alamos, New Mexico, in 2005. (AP/AP)

George Cowan, 92, a pioneer in nuclear chemistry, patron of the arts, and persuasive, visionary and enterprising figure who brought imagination and analytical abilities to the solution of problems in areas from finance to foreign affairs, died April 20 at his home in Los Alamos, N.M.

Friends said his death followed a fall, the Associated Press reported.

After playing an important role in the development of the atomic bomb, Dr. Cowan spent years as one of the key figures at the nuclear research center at Los Alamos, where the bomb had been built.

He joined the Los Alamos National Laboratory in 1949 and was a scientist and administrator there for 40 years.

In addition, Dr. Cowan was a kind of nuclear detective: More than 60 years ago, he used minute samples of nuclear debris, scattered by the winds, to help demonstrate to skeptical federal officials that the Soviet Union had tested its own atomic bomb.

It was a watershed moment, ending American dreams of a comfortable nuclear monopoly, giving impetus to the Cold War and helping determine the direction of great power politics for years to come.

A student of both the arcane details of weapons test detection and the philosophical connections between science and society, Dr. Cowan was a leader in organizing the vibrant civic, artistic, intellectual and financial institutions that grew up in the vicinity of Los Alamos.

Recognizing a need for research that cut across traditional scientific disciplines, he was the founding president in the 1980s of the Santa Fe Institute. The institute called him “a central figure in the history of transdisciplinary science.”

Early in his career, he helped analyze clues in the rays and particles scattered by the first Soviet atomic bomb test. He became, it could be argued, among the foremost of history’s bearers of bad tidings.

He and his team “were the first to go to Washington to convince President Harry S. Truman that the Russians had indeed tested an atomic bomb,” he said.

Dr. Cowan and his colleagues were credited with the discovery of new chemical elements in Soviet nuclear debris. Because of security requirements, the findings remained secret for years.

During the Reagan administration, Dr. Cowan was a member of the White House science council.

Of all his accomplishments and interests, the one that might seem least expected in a cerebral figure concerned with nature on the invisible scale was his work in organizing the Los Alamos National Bank in 1963.

He once said, according to the bank’s home page, that “the naivete of a bunch of scientists proposing to run a chartered bank” was what led the Office of the Comptroller of the Currency to turn thumbs down. But organizers, who included many Los Alamos managers, persisted. The bank was chartered and proved successful, and Dr. Cowan spent years on its board of directors.

He also was a board member of the Santa Fe Opera and was credited with providing it sound financial guidance.

George Arthur Cowan was born Feb. 15, 1920, in Worcester, Mass., and graduated in 1941 from Worcester Polytechnic Institute with a degree in chemistry. He then studied under future Nobel laureate Eugene Wigner at Princeton University, where he helped design a uranium chain reactor.

Along with Wigner, Dr. Cowan joined the efforts at the University of Chicago in 1942 in which Enrico Fermi created the first controlled nuclear reaction.

With the expertise he developed in the new science of nuclear fission, Dr. Cowan was sent around the country to help out at the scattered sites where scientists struggled with the many parts of the massive bomb-building project.

In 1950, he received his doctorate in physical chemistry from what was then the Carnegie Institute of Technology in Pittsburgh.

Two years ago, Dr. Cowan published a memoir called “Manhattan Project to the Santa Fe Institute.” He held the E.O. Lawrence and the Enrico Fermi awards, two of the top honors in the nuclear field.

His wife, chemist Helen “Satch” Dunham, died last year. The couple had no children.

Dr. Cowan recognized that modern challenges faced by the United States may dwarf even those of Manhattan Project days.

“The problems involved in dealing with a combination of depraved societies, rogue governments, dispersed militias and rampant thuggery have no precedent,” he said in 2006.

The Manhattan Project is still regarded as an almost unparalleled example of what might be achieved by an all-out effort of many of the world’s best minds.