By WILLIAM J. BROAD NY Times Published: October 24, 2006 VIENNA — Eager for precision in a field notorious for ambiguity and frustration, curators at top museums in Europe and the United States have long reached for the instruments of nuclear science to hit treasures of art with invisible rays. The resulting clues have helped answer vexing questions of provenance, age and authenticity.A view of the research reactor at the University of Missouri, a center that the Metropolitan Museum of Art has used in its research. Archaeological samples are bombarded with neutrons. The results reveal trace elements, which give new information about old sculptures in the museum’s collection. Metropolitan Museum of Art: Set in Stone Ed Alcock for The New York Times. A proton beam is used to study antique jewelry, top, at a Louvre laboratory, above. Now such insights are going global. The International Atomic Energy Agency, a United Nations unit best known for fighting the spread of nuclear arms, is working hard to foster such methods in the developing world, letting scientists and conservators in places like Peru, Ghana and Kazakhstan act as better custodians of their cultural heritage.