Self-induced zeeman coherences in a Paul trap

A new method for the measurement of motional frequencies and amplitudes of stored ions in a radio-frequency trap is presented. Ions oscillating in the trap potential and additionally subjected to a small magnetic field, undergo sublevel transitions between adjacent Zeeman states when their motional frequency is identical with the Larmor frequency in the applied magnetic field. These transitions can be sensitively detected by means of an optical pumping scheme. As they are related to a coherent superposition of adjacent states and originate from the inherent motion of the ions in a slightly inhomogeneous magnetic field, this phenomenon is termed self-induced Zeeman coherence.