Differential cascade feeding - 5-level example with n=3
1s2s3l
Quartet feeding
1s2s3l
Doublet feeding
1s2s3s 4S
1s2s3s 2S
1s2s2p 2P
1s2s2p 4P
1s2 1S + e-
1s22s 2S
1s22s 2S
 1s2s2p 4P should get more cascade feeding than 1s2s2p 2P
   since there is less lost to other channels!
 Ratio of 1s2s2p 4P / 1s2s2p 2P  should be relatively enhanced (Comment to PRL 2005)