Overview of the Various Options for Time Course Measurement using FTIR

Download PDF August 15, 2022


FTIR-4000 and 6000 Series spectrometers
FTIR-4000 and 6000 Series Spectrometers

FTIR offers three methods for time course measurement: interval measurement, rapid-scan, and step-scan; the time resolution is 1 sec, 50 msec, 5 msec (optional: 10 nsec) respectively.

Here we will review the basic features and measurement for each method. Each method uses a different type of scanning method for  the moving mirror in the interferometer. “Interval measurement” is performed with regular scanning and “rapid-scan measurement” uses a faster scan rate of the moving mirror. Using “step-scan measurement,” the moving mirror stops at each data-sampling point and perturbed at each of the points.


Measurement Conditions
Interval Measurement *1Time Res.: 1 sec ~Application: structural transition of a sample, monitoring of gas concentration
Measurement Ex.: Measure the transition of CO2 concentration in room air. (Fig. 1) Interval measurement is effective for long-time monitoring of gas analysis. *1 JASCO interval measurement program can be used for up to 60001 scans or 24 days.
Rapid-Scan MeasurementTime Res.: 50 msec ~Application: photo-polymerization reaction, orientation relaxation of polymer film
Measurement Ex.: The curing process of a UV cured resin was measured, a photo-polymerization reaction. (Fig. 2) The peak intensity transition at 1637 cm-1 (bottom of Fig. 2) is attributed to the C=C stretch. The peak intensity rapidly decreased responding to the UV irradiation and continued to decrease moderately indicating that the initial reaction and reaction process for photo-polymerization was observed very accurately.
Step-Scan Measurement*2Time Res.: 5 msec ~*3Application: relaxation of liquid crystal orientation
Measurement Ex.: The relaxation process of the orientation of a liquid crystal in response to an electric field was measured. (Fig. 3) The peak intensity transition at 2925 cm-1 (bottom of Fig. 3), is attributed to the C-H stretch. The peak intensity fluctuated responding to the power voltage being applied and stopped, and decreased in two phases - rapidly and then moderately. It is known that the liquid crystal in the area near the electrode has a faster orientation relaxation than the bulk and this difference can be observed.
*2 limited to the materials with repetitive response. *3 10 nsec ~ is optionally available.
CO2 concentration transition
Figure 1. CO2 concentration transition


Curing process of a UV cured resin
Figure 2. Curing process of a UV cured resin


Relaxation process of liquid crystal orientation
Figure 3. Relaxation process of liquid crystal orientation


FTIR, Step-scan, Rapid scan, Interval scan, resin curing, CO2,

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About the Author

Dr. Carlos Morillo received his Post Doc at Advanced Industrial Science & Technology in Fukuoka and was a Research Scientist at Kyushu University in Japan where he lived for several years. Carlos received his Doctor of Engineering from Kyushu University and his Masters and BS from Simon Bolivar University in Caracas Venezuela. He is an Applications Scientist at JASCO.