Raymond Davis Jr.
1914–2006, Washington, D.C., United States, Blue Point, New York, United States
American chemist-physicist, pioneer of neutrino astronomy with the Homestake experiment that uncovered the 'solar neutrino problem'.
Davis earned his PhD in chemistry at Yale in 1942 and spent almost his entire career at Brookhaven National Laboratory. He devised a radiochemical neutrino detector: a 615-tonne tank of tetrachloroethylene placed 1,478 m deep in the Homestake gold mine, South Dakota.
From 1970, the experiment recorded only about one-third of the solar neutrinos theory predicted — the 'solar neutrino problem' that persisted for three decades until neutrino oscillations were confirmed. In 2002, aged 88, he shared the Nobel Prize in Physics for pioneering neutrino astronomy.
Nobel-winning work
Davis's Homestake experiment used the reaction ν + ³⁷Cl → ³⁷Ar + e⁻: each captured electron neutrino converted a chlorine atom into radioactive argon, countable atom by atom. The 380,000-liter perchloroethylene tank sat deep underground to shield cosmic rays.
Results published from 1968–1970 showed the measured solar-neutrino flux at only ~1/3 of the standard solar model's prediction (Bahcall). After decades of scrutiny, the deficit was explained by neutrino oscillations — electron neutrinos morphing into muon/tau neutrinos en route to Earth — meaning neutrinos have mass. It was the first time particles carried information from the Sun's core, opening neutrino astronomy and giving the first experimental evidence for physics beyond the Standard Model.
Workplaces: Brookhaven National Laboratory, University of Pennsylvania
United States