INFRARED LINEAR DICHROISM SPECTROSCOPY BY A DOUBLE MODULATION TECHNIQUE

A linear IR dichroism experiment has been devised using a FTIR instrument in combination with a photoelastic modulator. Based on the Mueller-Stokes calculus, a method to directly obtain the absorbance spectra A vparallel and A vperpendicular from the modulated interferogram is developped, which allows the sensitive evaluation of the dichroic ratio. The photoelastic modulator, in combination with a FTIR instrument, offers high sensitivity, high speed, excellent signal to noise ratio and a broad spectral range from 3300 to 850 cm-1. First experimental results obstained from SBS block copolymer are reported. © 1990 Springer-Verlag.