The Willis E. Lamb Award

Professor Willis Lamb was best known for his experimental discovery of a minute difference in the energy of the electron orbiting the nucleus of an atom of hydrogen, known as the fine structure of the hydrogen atom. This showed that there was a discrepancy (known as the Lamb shift) in the quantum theory describing the behaviour of the electron in the hydrogen atom. He shared the 1955 Nobel Prize for Physics for this work.

Lamb’s discovery revolutionised the quantum theory of matter and led physicists to reconsider the fundamental concepts behind the application of quantum theory to electromagnetism, laying the foundations of quantum electrodynamics, a key subject in modern physics. In 1947 the Nobel Prize-winning physicist Isidor Rabi described Lamb’s work as “the most significant advance in 15 years in the knowledge of the atom”.

A hydrogen atom consists simply of a proton with an electron moving around it in an orbit. The space between the proton and the electron was classically thought to be empty. But quantum electrodynamics postulates that empty space is in fact not empty but contains “virtual” particles that appear and disappear so quickly that they cannot be detected.

The Lamb shift occurs when the electron orbiting the hydrogen atom collides with virtual particles. The collision slightly alters the electron’s orbit, resulting in a small change in the energy of the electron, which is determined by the precise position of the electron relative to the proton.

Lamb’s experiment involved focusing microwaves on a beam of hydrogen atoms to stimulate transitions between the two energy states. He was able to show that if the electron received some energy it changed from a stable to an unstable state; he was able to measure precisely the difference in the energy levels between the two states.

Before the results of Lamb’s experiment were known it was assumed that the two states of the hydrogen atom had the same energy. This was the assumption made by Paul Dirac when he derived his basic formula of quantum mechanics.

A series of remarkable papers written by Lamb, published in the scientific journal Physical Review between 1947 and 1953, became instant classics for atomic physicists and were given to many students as a starting point for learning modern atomic physics.

Willis Eugene Lamb was born in 1913 in Los Angeles. His father was a telephone engineer. He was educated in schools in Oakland, California, and Los Angeles where he excelled in chemistry. In 1930 he entered the University of California at Berkeley and received his bachelors degree in chemistry in 1934.

He continued as a postgraduate student in the University of California and was awarded his PhD in theoretical physics in 1938. The famous physicist Robert Oppenheimer, who later directed the Manhattan Project that developed the first nuclear weapon, supervised his thesis research, on the electromagnetic properties of nuclear systems.

In 1938 Lamb joined Columbia University as a lecturer in physics. He was appointed assistant professor in 1945, associate professor in 1947, and professor in 1948. Between 1943 and 1946 he also worked on radar and microwave research for the US Office of Scientific Research and Development.

Between 1943 and 1951 he was also associated with the Columbia Radiation Laboratory where the research that won him his Nobel prize was done. In 1951 he moved to Stanford University in California as Professor of Physics.

In 1953-54 he was Morris Loeb Lecturer at Harvard. Between 1956 and 1962 he worked in the UK as a Fellow of New College and Wykeham Professor of Physics at the University of Oxford. In 1962 he moved back to the US to become the Henry Ford Professor of Physics, and later the J. Willard Gibbs Professor, at Yale. In 1974 he moved to the University of Arizona at Tucson, to take up an appointment of Professor of Physics and Optical Sciences. He remained at this post until he retired in 2002. He continued to work at the university during his retirement, however, until shortly before he died.

Lamb’s research covered an unusually wide range of topics in physics, among them: the theory of the interactions of neutrons and matter; theories of the structure of nuclei; a study of fluctuations in cosmic ray showers; the theory and design of magnetron oscillators; the theory of a microwave spectroscope; and the study of the fine structure of hydrogen, deuterium and helium.

Some of this research was sponsored by the US Army Signal Corps and the US Office of Naval Research, introducing him to experimental work with magnetrons and sealed vacuum tubes.

In addition to the Nobel prize Lamb received numerous honours and awards and held many visiting lectureships. In 1953 he received the Rumford Premium of the American Academy of Arts and Sciences.

He was awarded numerous honorary doctorates. He received the Research Corporation Award in 1955. He was a member of the National Academy of Sciences, and a Fellow of the American Physical Society. In 2000 he received the National Medal for Science, the US’s highest scientific honour.

A brilliant scientist, Lamb was also an engaging personality, though shy and very modest. He had a subtle wit and a great joy of life. He was an enthusiastic swimmer and a keen sailor.

His first wife died in 1996. He was divorced from his second wife. His third wife survives him.

Professor Willis Lamb, Nobel prize-winning physicist, was born on July 12, 1913. He died on May 15, 2008, aged 94