Optical Pumping Advanced Laboratory Instrument by TeachSpin: Experiments

Optical Pumping

Students will explore the interaction of the alkali atom with a weak magnetic field, as described by the theoretical perturbation calculations known as the Briet-Rabi equation. This equation is:

equasion

is the interaction energy, is the hyperfine splitting energy and is the externally applied magnetic field.

Figure 2 shows the optical pumping signals for zero and very low magnetic fields. Both the Rb⁸⁵ and Rb⁸⁷ isotopes produce only unresolved single lines in these low fields. However, when the magnetic field is increased, each single line splits into resolved hyperfine lines, as shown in Figure 3. This data can be compared to the Briet-Rabi predictions. Double quantum transitions are also detected on this data. They can be studied as a function of rf power.

Both optical pumping times and the so-called Rabi oscillations can be studied by gating the rf power on and off at low magnetic fields. Figure 4 shows a measure of the optical pumping time when the rf power has been turned off and Figure 5 is an exploded view of the signal after the rf has been gated on. It clearly shows the oscillations of the transmitted light which are interpreted as precession of the atomic magnetization about the rf magnetic field. They can be studied as a function of rf power.
Other experiments include (but are not limited to) magnetic field reversal, photon absorption, spin exchange, effect of buffer gases on optical pumping and temperature dependence of all of the above experiments. The instrument even includes a second mounted linear polarizer for students to study circularly polarized light.