German physicist who shared one-half of the Nobel Prize for Physics in 1989 with the German-born American physicist Hans G. Dehmelt (Dehmelt, Hans Georg). (The other half of the prize was awarded to the American physicist Norman F. Ramsey (Ramsey, Norman Foster).) Paul received his share of the prize for his development of the Paul trap—an electromagnetic device that captures ions (electrically charged atoms) and holds them long enough for their properties to be accurately measured.

Paul studied at technological institutes in Munich and Berlin and received a doctoral degree in physics from the Technical University in Berlin in 1939. He became a lecturer at the University of Göttingen in 1944 and was a full professor there from 1950. From 1952 he also taught at the University of Bonn.

The Paul trap, which he developed in the 1950s, used a radio-frequency current to maintain an alternating electric field that isolates and confines charged particles and atoms in a small space. The Paul trap allowed physicists to study atomic properties and test physical theories with high degrees of precision and became an important tool in modern spectroscopy. Paul also invented a way of separating ions of different masses and storing them in the Paul trap, using a principle that was subsequently widely applied in modern spectrometers.