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. Author manuscript; available in PMC: 2018 Jan 18.
Published in final edited form as: Chemistry. 2016 Dec 5;23(4):725–751. doi: 10.1002/chem.201603884

Figure 1.

Figure 1

Schematic representations of SEOP.[2b, 4] (a) SEOP cell containing a noble gas (here, Xe), buffer gases (e.g. N2), and a small quantity of vaporized alkali metal (here, Rb); the cell is irradiated by circularly polarized laser light that can be absorbed by the alkali metal atoms. (b) The first step of SEOP: in order to conserve angular momentum, photon absorption results in selective population depletion from one Rb ground electronic state (neglecting Rb nuclear spin for simplicity). Although gas-phase collisions work to equalize the excited-state populations (and hence, the ground-state repopulation rates), continuous depletion of one state by the laser leaves the AM vapor electronically spin-polarized. (c) The second step of SEOP: Gas-phase collisions occasionally allow spin order to be transferred from the AM atom electrons to the noble gas nuclei via Fermi contact hyperfine interactions, thereby hyperpolarizing the noble gas over time. Reproduced with permission from Ref. [36] © John Wiley & Sons, Ltd., 2015.