Dictionary:Fig O-4

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FIG. O-4. Optical pumping. (a) Assume three possible energy levels A1, A2, and B where under normal conditions atoms occupy the ground states A1 and A2, which differ in energy by only a very small amount (1). If we irradiate a sample with light from which the line A1B has been removed (2), atoms in A1 can rise to B but not those in A2. When the atoms fall back to the ground state, they are as likely to fall to A2 as to A1 (3); the result will be depletion of A1 and overpopulation of A2. (7) shows the completion of pumping and (8) the nullifying effect of an RF signal. (b) Schematic of measurements without pumping (above), with complete pumping (center), and when pumping effect is nullified (below). (From Telford et al., 1990.)