Optical pumping in rubidium

This elegant experiment introduces the double resonance technique, whereby magnetic resonance transitions are detected by optical absorption. Circularly polarized light from a Rb lamp passes through a cell containing Rb vapor. A weak magnetic field is applied to the cell, splitting the ground state sublevels. Transition rules are invoked to explain how the population of these sublevels becomes inverted, with the result that optical transitions from the ground state to the first excited state are greatly reduced. Re-distribution among the ground state sublevels is achieved by application of a radio-frequency field, resulting in increased optical absorption in the cell. The magnitude of the magnetic field is thus measured by frequency, a parameter readily measured to high accuracy, making this double resonance technique useful as a highly sensitive magnetic field probe.

Experiment Information