Sadtler also produced the set in digital form. Dr. Ruelle Ghislain of Belgian Railways has written from their Polymer lab to enquire if we can give any advice on far infrared sampling. Ruelle uses a P-E 2000 and has experience of mid IR, but wants to know what tricks are required in the longer wavelength region. Another problem with all FTIRs is that the window in the interferometer case must transmit the infrared or be removed. Removal leads to problems unless you have a reliable flushing gas.
Replacement is a problem.
A thin Mylar window will do but it must be thin or you will have problems in the mid i.r. 2.5 thick film is available but a special holder would be required and it is fragile and you will get problems with interference fringes. The real killer in the far infrared is the absorption caused by the rotational spectrum of water vapour. Water has 3 axes of rotation all with different moments of inertia hence the rotational spectrum is very complex. Absorption is very intense and the path length for the absorption process is the total distance from the source to the detector. So you must reduce the water level to almost nothing.