HIGH RESOLUTION GRILLE SPECTROMETERS FOR ROTATIONAL MOLECULAR ANALYSIS BETWEEN $2000 CM^{-1}$ AND $225 CM^{-1}$

Abstract

Two different types of grille spectrometers are considered for high resolution infrared studies. Spectra of the $\nu_{8}$ band of methane near $1300 cm^{-1}$ were studied with a single beam “dual grille spectrometer.” The resolving limit varied from 0.05 to $0.07 cm^{-1}$, so that the Q branch is well resolved. Absolute wavelengths reference marks are supplied by spectral lamps, the interpolation being interferometrically achieved. Calibration accuracy is about $0.004 cm^{-1}$. For the spectral range $500-225 cm^{-1}$, a single grille spectrometer was specially designed. It has been used for the study of the $\nu_{8}$ band of methyl cyauide near $360 cm^{-1}$. The resolving limit is $0.2 cm^{-1}$.