Robert Curtis Retherford

…American physicists Willis Lamb and Robert Retherford discovered that the levels actually differ by roughly 10⁹ hertz (see below X-ray and radio-frequency spectroscopy: Radio-frequency spectroscopy: Methods). In contrast, the transition frequency between the ground state and the first excited states was calculated as approximately 2.5 × 10¹⁵ hertz. Two American…

…American physicists, Willis Lamb and Robert Retherford. Their experiment measured the energy difference between two nearly coincident levels in hydrogen, designated as 2²S_1/2 and 2²P_1/2. Although optical measurements had indicated that these levels might differ in energy, the measurements were complex and were open to alternative interpretations. Atomic theory at…

, and Robert C. Retherford of the United States, employing the novel microwave techniques that wartime radar contributed to peacetime research, were able not only to detect the energy difference between the two levels directly but to measure it rather precisely as well. The difference in energy,…