Norman F. RamseyProfessor

According to the laws of quantum mechanics, atoms can have only fixed energy levels. When there are transitions among different energy levels, electromagnetic radiation with certain frequencies is emitted or absorbed. After Isaac Isidor Rabi developed a method to determine these frequencies by passing a beam of atoms through a magnetic and electromagnetic field, Norman Ramsey refined the method in 1949 through the interference of two electromagnetic fields. This improved precision and became the basis for the atomic clock.