Fine structure of the hydrogen atom by a microwave method. Offprint from: The Physical Review, Vol. 72, No. 3, 1 August 1947

THE LAMB SHIFT - NOBEL PRIZE IN PHYSICS 1955. First edition, very rare offprint, signed by Lamb, who received a half-share of the 1955 Nobel Prize in Physics for this work. The Lamb-Retherford experiment of 1947 was the first to measure what is now known as the Lamb shift-the difference in energy between two energy levels 2S½ and 2P½ of the hydrogen atom-which had not been correctly predicted by the Dirac relativistic wave equation. "The Lamb shift experiment was a landmark in 20th-century physics" (Biographical Memoir, National Academy of Sciences). "After it was reported at Shelter Island, [the Lamb-Retherford experiment] became the point of departure for the renormalization program" (Silvan Schweber). Lamb (1913-2008) received his doctorate at Berkeley in 1938 under the guidance of J. Robert Oppenheimer. "Unlike many of his generation of physicists, Lamb did not follow Oppenheimer into the wartime atom-bomb project. Instead, he concentrated on his specialisms - microwaves and radar - at Columbia University in New York, performing the experiments that culminated in the observation of the Lamb shift. This shift is a tiny difference in energy between two atomic orbitals in hydrogen, denoted 2S and 2P, distinguished only by their angular momenta. Quantum theories of the time predicted that these levels should have identical energies. The discovery that they did not demanded a fundamental theoretical rethink - one that was initiated almost immediately by Hans Bethe. The Lamb shift thus became a cornerstone of the modern edifice of quantum electrodynamics (QED). This, the quantum field theory of the electromagnetic interaction, explains the shift as resulting from energy fluctuations in the vacuum that smear out the position of the electron in a hydrogen atom. This process has a greater effect on the Coulomb energy of the electron's binding to the central proton at smaller radii (where the 2S state is most likely) than at larger radii (where the 2P state dominates). Today, precise measurements of the Lamb shift have tested QED to an accuracy of better than one part in a million" (Sargent). On Lamb's 65th birthday, Freeman Dyson wrote, "those years, when the lamb shift was the central theme of physics, were golden years for all the physicists of my generation. You were the first to see that this tiny shift, so elusive and hard to measure, would clarify in a fundamental way our thinking about particles and fields." Not on OCLC or RBH. Provenance: Willis Lamb (signature on front wrapper). Lamb was born in Los Angeles, the son of a telephone engineer. He entered the University of California at Berkeley in 1930, where he earned a bachelor's degree in chemistry (1934). Lamb continued at Berkeley as a graduate student in theoretical physics directed by J. Robert Oppenheimer, receiving his doctorate in 1938. In that year Lamb joined the faculty at Columbia University, New York, where he carried out research in microwaves and radar. His defence-related investigations focused on the problem of how to make shorter, higher frequency microwave sources for radar. It was this that would eventually lead to a Nobel prize in 1955. Lamb continued working in atomic spectroscopy and laser physics at Stanford University (1951-56), where he devised microwave techniques for examining the hyperfine structure of the spectral lines of helium, and then as professor at Oxford (1956-62). He returned to the US in 1962 as Henry Ford II professor of physics at Yale, joining the University of Arizona in 1974 until his retirement in 2002. "In the second quarter of the 20th century, quantum theory faced some serious challenges, including unexplained details of atomic spectra and difficulties in calculating basic properties of charged particles. In 1947 Willis Lamb and Robert Retherford of Columbia University discovered an unexpected detail in the hydrogen spectrum, later called the Lamb shift, that became an essential clue in solving both problems. The measurement.…