A high resolution Fourier transform spectrometer has been constructed for working in the far infrared region. After a description of this instrument, its performance in the 10–40 cm-1 spectral region is demonstrated by studying the pure rotational spectra of CH3Cl and CH3Br. A working resolution of 0.05 cm-1 is verified, and isotopic splitting is observed in CH3Br out to 14 cm-1.
Jacques Pesenti and Michèle Sergent-Rozey, "Étude par transformation de Fourier de CH3Br et CH3Cl dans l’infrarouge très lointain," Appl. Opt. 13, 1158-1163 (1974)