Infrared Intensities in Liquids II: Accuracy of FT-IR Transmission Measurements

The absorption intensities of organic liquids have recently been measured against a primary standard by dispersive spectroscopy. No primary standard is known that can be used with rapid-scanning FT-IR spectrometers. Accordingly, we have remeasured the absorption intensities of C 6 H 6 C(ℓ ), CH 2 C1 2 (ℓ ), and C 6 F 6 (ℓ ), largely in 500-μm thick cells, by FT-IR spectroscopy, and we compare the results with those of the calibrated dispersive spectroscopy. The agreement is excellent. Further evidence about the reproducibility of the intensities of these bands in different laboratories and on different instruments is desirable, because some of these bands may prove to be useful as secondary standards of photometric accuracy in transmission spectroscopy.