Q: MCT detectors used in infrared microscopes have different wavenumber ranges. On what basis should I select my detector?

A : The Shimadzu AIMsight infrared microscope offers the standard Type II Superlattice (T2SL) detector and the optional DLATGS detector. T2SL detector is more sensitive than the DLATGS and can measure across a wavenumber range from 5000 to 700 cm-1, whereas DLATGS extends further to the low-wavenumber end and covers a range from 4600 to 400cm-1.

The T2SL detector is the environmentally friendly, mercury-free version of the more commonly known predecessor, MCT. There is no compromise in performance or sensitivity with the T2SL, as they are equivalent to the MCT.

If the characteristic peak of interest resides below 700 cm-1, then a DLATGS detector may be necessary. As a reference, the diagram below shows the spectra of polymers with absorption in the 700 to 650 cm-1 range. From top to bottom, these polymers are polystyrene (PS), polyethylene (PE), polybutadiene (BR), polyvinyl chloride (PVC), and polyvinylidene chloride (PVDC). The absorption near 700 to 650 cm-1 results from C-H out-of-plane vibrations and C-Cl stretching vibrations.