Introduction

Infrared microspectroscopy is a non-destructive and versatile experimental technique to study chemical and structural information based on the vibrations of molecular bonds in samples which have resonant frequency to infrared light's one. When an intense wavelength of infrared light is passed through a sample , the vibrations occur with molecules causing absorbance of infrared due to a change of dipole moment. The unabsorbed infrared light passes through the sample to be detected by a IR detector which a computer will interpret the IR intensity in a relative form of IR absorbance and frequencies in an unit of wavenumber (cm-1) that presents in a form of IR spectrum.  The IR spectrum of each molecule of a substance has unique characteristics that absorbs infrared light at different frequencies depending on the chemical bonds and the atomic weight of the functional groups within the sample. Each spectral signal represents vibrational modes of protein, lipid, carbohydrate, carbonyl group or aromatic group, etc. that is commonly denoted a fingerprint, as it provides a unique spectral signature of the sample in interest. This technique is therefore suitable for studying chemical structure from various types of sample without damaging the sample during measurement such as biological sciences, materials science, forensic science, environment as well as cultural heritage. 

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The use of a synchrotron source in infrared microspectroscopy has enhanced lateral resolution, faster acquisition time and superior spectral quality because of high brightness, small source size and narrow range of emission angles in compared to a conventional infrared source. It has improved signal-to-noise ratio in IR spectrum without loss of spatial resolution that benefits to application on biological sciences significantly. 

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The beamline for infrared microspectroscopy, so called Beamline 4.1: µ-IR, has been constructed to provide infrared microspectroscopy technique in a spectral range of mid-infrared (4,000 - 400 cm-1) to public users since 2010 and has been developed continually. With the synchrotron radiation emitted from SPS-I, it offers high-brilliance and collimation of the SR beam coupled with Vertex 70 spectrometer and Hyperion 2000 IR microscope (Bruker) to enable the analysis at diffraction-limited spatial resolutions from 5 to 20 microns on microscopic samples such as single biological cells, complex biological system, old paints, thin films, and so on.