(1913–    ), American physicist and Nobel laureate best known for his research on atomic spectroscopy and laser physics, including the discovery of the quantum effect now called the Lamb shift.

Lamb was born on July 12, 1913, in Los Angeles, Calif., and earned a bachelor's degree in chemistry (1934) and a Ph.D. in physics (1938) from the University of California at Berkeley; he wrote his dissertation, on the electromagnetic properties of nuclear systems, under the direction of J. Robert Oppenheimer. Lamb held academic positions at Columbia University (1938–51), Stanford University (1951–56), Oxford (1956–62), and Yale (1962–74). From 1974 to 2003 he was a professor of physics and optical sciences at the University of Arizona.

He worked on high-frequency microwave sources for radar during and after World War II, and this led to the discovery in 1947 of the Lamb shift, which involves the “fine structure” of the hydrogen spectrum. The hydrogen atom possesses a single electron, which can exist only in distinct energy states, which are evidenced in the spectrum. According to a prominent theory of the fine structure that had been put forth by British physicist Paul Dirac, certain energy states should be essentially equivalent. Using a high-resolution radio-frequency resonance method, Lamb showed that such states actually differ slightly in energy, and he made highly accurate measurements of this “shift.” He thereby helped reshape the theory of the interaction of electrically charged particles and electromagnetic fields, the so-called quantum electrodynamics, fundamental to the study of elementary particles.

In 1955 he received the Nobel Prize in physics jointly with the American physicist Polykarp Kusch for their separate contributions to knowledge of the interaction of electrons and electromagnetic radiation. Lamb was cited “for his discoveries concerning the fine structure of the hydrogen spectrum.” He became a member of the U.S. National Academy of Sciences in 1954, and in 2000 was awarded the National Medal of Science for “his towering contributions to classical and quantum theories of laser radiation and quantum optics, and to the proper interpretation of nonrelativistic quantum mechanics.”