Definition
Alfred Kastler (1902-1984) was a French physicist who revolutionized the study of atomic energy levels. His development of optical pumping involved using light to manipulate the energy states of atoms. This technique enabled precise measurements and control of atomic behavior. He essentially invented a method to 'tune' atoms with light, like adjusting a radio. Kastler's work is fundamental to lasers, atomic clocks, and magnetic resonance imaging. For his achievements, he was awarded the Nobel Prize in Physics in 1966.