Microscale spectroscopic thermal imaging of n-alkanes

Abstract

We have developed an instrument for the measurement of microscale infrared (IR) spectroscopic thermal images in a dynamic mode. The high speed image processing based on the two-image technique enables a simultaneous spectroscopic and thermal imaging that detects a dynamic change of IR absorption spectrum by a transmission mode, and the emission of IR radiation from the sample surface. With this dynamic mode scan at 200 Hz, the spectra at any temperatures are free from the base line variation that comes from the temperature dependent surface emission signal, which can be subtracted from the total signal. In addition, the precise calibration between temperature–emissivity in phase transitions has become possible. The phase transitions, from liquid to hexagonal–monoclinic crystal systems, of normal tetracosane (n-C24H50), is presented as an example of the dynamic mode spectroscopic thermal imaging in microscale of normal alkane.