You can decrease the working distance between the sample and the system or decrease resolution of spectra (probably it would help more). Also for some samples this method can not show a good results

Lots of basic questions spring to mind.  The first are a). is the sample in focus? b). what is the window material in the cell? Is the measurement being performed in Transmission or Reflectance?  A discussion about your sample prep and instrument set-up may help in resolving your problem.

Hi Donald, thanks, good questions.

(a) Yes, the sample is in focus

(b) window material is CaF2

(c) Transmission measurements

Nothing unusual in your responses.  Next thoughts.

1. Do you get a good background single beam spectrum? And 100% line?

2. How does the single beam spectrum to the background compare?  If poor take a look at the thickness of your sample.  I normally compress a tiny amount of material onto the sample support material.  I use a diamond mount - what are you using? 

1. The background spectra through one of the CaF2 windows (top window-optimised working distance) of the cell looks fine. However, background spectra from the second CaF2 window (non-optimal working distance) looks very noisy.

2. Transmission spectra of the sample looks normal, so I dont think the thickness of the sample is an issue. 

I think the issue here is my inability to optimise the working distance for the second CaF2 window.

Thank you for your interest!

Hi, I know this is an old topic, however it would be nice to know if you succeeded with this experiment? If so, what was the highest humidity applied in the MCell? Thank you

Apologies I dropped off the thread. My next step would be to ensure the objective and condenser were properly corrected for the window and sample support materials. Also check that the condenser is properly aligned with the system apertures.