Vacuum pumped FT-IR spectrometer for minimizing signals from atmospheric water and CO2. Equipped with detectors and light sources for MIR (DTGS and MCT) and FIR (DTGS). Accessories for in-situ transmittance and reflectance measurements on films and powders. Gas cell for gas samples. Gas flow to in-situ cells controlled by a set of MFC controllers allowing for user selectable gas mixtures. ATR accesories with different path length and crystals for measuring solid and liquid samples.