Infrared circular dichroism and linear dichroism spectrophotometer

Area of Science:

• Spectroscopy
• Physical Chemistry
• Materials Science

Background:

• Circular dichroism (CD) and linear dichroism (LD) are powerful spectroscopic techniques for probing molecular structure and electronic transitions.
• Existing instrumentation may have limitations in spectral range, precision, or the ability to perform both CD and LD measurements simultaneously.

Purpose of the Study:

• To describe a novel instrument capable of measuring infrared (IR) circular dichroism (CD) and high-precision linear dichroism (LD).
• To detail the instrument's performance and its application in studying various materials.

Main Methods:

• Utilized a germanium photoelastic modulator for polarization modulation of monochromatic IR light (5000 cm⁻¹ to 750 cm⁻¹).
• Employed a cooled InSb or HgCdTe detector for signal acquisition.
• Implemented phase-sensitive demodulation for CD measurement with high precision (4 x 10⁻⁶ o.d. units).

Main Results:

• Successfully measured IR CD arising from molecular vibrations in cholesteric liquid crystals, crystals, and fluids.
• Demonstrated the capability to study CD from electronic transitions in metal complexes.
• Showcased the instrument's utility for analyzing linear dichroism in polymer films.

Conclusions:

• The developed instrument offers a versatile platform for advanced spectroscopic analysis in the infrared region.
• It provides high precision for CD and LD measurements, expanding the scope of vibrational and electronic spectroscopy.
• The instrument facilitates the investigation of molecular properties in diverse condensed phases and materials.