NEW YORK -- Raymond Davis Jr., who shared the 2002 Nobel Prize in Physics for detecting particles produced by nuclear reactions in the sun, has died at his home on Long Island. He was 91.
His death on Wednesday was announced by Brookhaven National Laboratory, a US Department of Energy facility where Mr. Davis was a chemist for four decades before retiring in 1984. The cause was complications from Alzheimer's disease, it said.
Mr. Davis' s prizewinning work on solar neutrinos took him to figurative highs and literal lows.
Starting in the 1960s, he constructed giant underground chambers in an attempt to detect the particles, which are produced in massive quantities by atomic action in the sun's core, but are so small and fast, they can pass through almost any solid matter without slowing down.
Working first in an Ohio mine, 2,300 feet down, then at the Homestake Gold Mine in South Dakota, 4,800 feet deep, Mr. Davis built detectors that looked for one of the few telltales of a neutrino's existence: a small amount of radioactive argon produced when one of the elusive particles collides with the nucleus of a chlorine atom.
It took years of refinements before the detectors saw anything, but by the 1970s Mr. Davis had become the first scientist to detect the particles -- a feat a Nobel committee called ``considerably more difficult than finding a particular grain of sand in the whole of the Sahara desert."
His experiments, conducted underground to eliminate interference from cosmic rays, helped confirm that the sun is powered by nuclear fusion and prompted further scientific inquiry that suggested that solar neutrinos, unlike light particles, have a small amount of mass.
Mr. Davis shared the 2002 physics prize with Masatoshi Koshiba, of Japan, and Riccardo Giacconi of the United States.
Born in Washington, D.C., he graduated from the University of Maryland and received his doctorate in physical chemistry from Yale University in 1942.
Mr. Davis served in the armed forces during World War II and worked for two years at the Monsanto Chemical Company before joining Brookhaven Lab's chemistry department in 1948. He was named the lab's senior chemist in 1964.
Between 1971 to 1973, he was part of the NASA board analyzing lunar dust and rocks brought back to Earth by the crew of Apollo 11.
After his retirement from Brookhaven, he worked as a research professor at the University of Pennsylvania.
Mr. Davis, who lived in Blue Point, leaves his wife, Anna, three sons, two daughters, and 11 grandchildren.