Coming from Oak Park (Ill.) High School, he played in the Band and orchestra and belonged to Cloister. After graduating with high honors in physics, he earned a master’s degree and a Ph.D. in nuclear physics at the University of Wisconsin.
Following academic stints at the University of North Carolina, Columbia, and Ohio State, in 1963 Keith joined the physics department of Brookhaven National Laboratory, where he had spent the summers of 1949 and 1950. In 1984 he transferred to environmental and climate science. During his career he published more than 300 papers in peer-reviewed scientific literature and authored or co-authored more than 40 book chapters. Late in his career he became involved with implementing projects to support science education in Long Island schools, lecturing on topics related to environmental science.
When Keith retired in 2012, he was granted emeritus status and praised for his significant contributions to atomic physics.
He greatly enjoyed hiking in France, opera, and photography.
Keith is survived by his wife of 63 years, Julie; daughters Caitlin, Margaret, and Megan; and five grandchildren.