$F'=2$ level (266.657 MHz lower) and the second to the $F'=1$ level (423.600 MHz lower). Each of these will cause three additional transparency peaks from the mechanisms discussed above. The first velocity class moves at 208 m/s and will cause peaks at $-156.943$ MHz, 0, and $+266.657$ MHz, i.e., a set of peaks shifted up by 266.657 MHz. The second velocity class moves at 330 m/s and will cause peaks at 0, $156.943$ MHz, and $+423.600$ MHz, i.e., a set of peaks shifted up by 423.600 MHz. Thus there will be 7 peaks in all, with 3 real peaks and 4 spurious ones. However, only the peak at $-156.943$ MHz will appear within the spectrum, caused by the probe driving the $F=2 \rightarrow F'=2$ transition and the pump driving the $F=2 \rightarrow F'=1$ transition. The other three spurious peaks will lie outside the spectrum to the right. This is indeed what is observed in Fig.\[satabs\](b): there is a small peak at $-157$ MHz within the spectrum.

The above explanation is borne out by the calculated spectrum shown in Fig. \[satabs\](c). Using a density-matrix formulation, we can calculate the absorption of a probe laser in a V-type system [@DAN05]. The calculation 