Photo from the Nobel Foundation archive.
Willis Eugene Lamb
Born: 12 July 1913, Los Angeles, CA, USA
Died: 15 May 2008, Tucson, AZ, USA
Affiliation at the time of the award: Stanford University, Stanford, CA, USA
Prize motivation: "for his discoveries concerning the fine structure of the hydrogen spectrum."
Prize share: 1/2
According to Niels Bohr's atomic model, a photon is emitted when an electron descends to a lower energy level. This results in a spectrum with lines corresponding to the different energy levels of different atoms. It appeared that the lines were divided into several lines close to one another, which Paul Dirac tried to explain in a theory. However, in 1947 Willis Lamb used precise measurements to establish what became known as the Lamb shift: what ought to have been a single energy level in the hydrogen atom according to Paul Dirac's theory actually was two nearby levels with a small difference in energy.