Pulse propagation.

		*  -------- |4>
		*    \        
		*     \ E3    -------- |3>  
		*      \       /    \
		*       \  E2 /      \ 
		*        \   /        \ E1
		*       ------- |2>    \
		*                       \
		*                    ------- |1>

Probe field only, the probe absorbed at a very short distance
./Nlevels_no_dopler_with_z.run  --E1o 5 --E2o 0.0  --E3o 0.0

Slow light
./Nlevels_no_dopler_with_z.run  --E1o 5 --E2o 35e6 --E3o 0.0

N-laser-system is on, probe field (E1) absorbed at short distance, 
very similar to just the probe fielf on
./Nlevels_no_dopler_with_z.run  --E1o 5 --E2o 35e6 --E3o 5e6

Interesting interaction of E1=E2 in the presence of E3
./Nlevels_no_dopler_with_z.run --E1o=36e6 --E2o=36e6 --E3o=90.0e6 --delta3=12e6