1. From our current understanding (Jim, I and Ahmad - postdoc at Princeton) other lines should exhibit the same effect. I have searched for the same effect in the other lines, but I see no broadening whatsoever. This is summarized in plot ``Summary_result''. The plot shows the `full width half maximum'' and the ``full width 1.5% maximum''. The label categorized transitions with different lower levels. The lorentzian broadening would exhibit as high number for `full width 1.5% maximum'', without the large effect in FWHM. We see that this is indeed the case for the lines exhibit resonance broadening in Argon. Such effect is not seen in Neon and Krypton.

Current working hypothesis is that the conditions for Argon are substantially different than in other lamps, because this is Mercury-Argon lamp. This is not fully satisfactory, because even it is quite different we expect that both Neon and Krypton are in the state where many atoms are in the ground state, so we would still expect to see some broadening. Some further investigation of relevant equations might shad some light. 

Based on insight from last paragraph Jim wants to see if the effect is there in the pure Argon lamp. Theoretically LAM should have Argon lamp (fmadec) but it is not clear if that was actually Argon lamp (PIPE2D-417). If there is no Argon lamp available, one should be purchased. 

2. Resonance broadening does not create shift of the lines. Other types migth shift lines, but the resonance broadening responsible for broad Argon lines does not create shifts.

3. Only one lower level will create resonance broadening. No other levels will create this type of broadening.

4. Discussion with Ahmad have been very useful. Email to pundits - I still have to do. 

I sent a conclusion email to pundits on Jun 17, 2020. Closing this ticket.