Lamb inverted

Since the main contribution to the uncertainty of the theoretical value of the IS Lamb shift comes from the uncertainty of the proton charge radius we can invert the problem and calculate the proton radius using the average of the self-consistent Lamb shifts in Table 12.3 L IS) = 8 172 847 (14) as input. Then we obtain the optical value of the proton charge radius... 

E. Arimondo, P. Glorieux, T. Oka, Observation of inverted infrared lamb dips in separated optical isomers. Opt. Commun. 23 (1977) 369-372. 

Fig. 3.5 Production of inverted Lamb dip in a gas laser with an intracavity low-pressure...

Fig. 3.6 Observation of an inverted Lamb dip in a He-Ne laser at 3.39 /xm with an intracavity CH4 absorbing cell. Output power versus laser-cavity tuning, with double scan. The saturated absorption peak has an amplitude of about 2% with a 400 kHz width, and is nicely centered on the °Ne Doppler gain curve. (Reprinted from Barger and Hall 1969, with courtesy and permission of the American Physical Society.)...

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