In situ Second-Harmonic Generation Circular Dichroism with Submonolayer Sensitivity.

Area of Science:

• Optics and Photonics
• Materials Science
• Physical Chemistry

Background:

• Optical activity is crucial for understanding chiral molecules.
• Existing methods for studying optical activity can be limited in scope or sample preparation.
• Ultra-high vacuum (UHV) conditions offer a controlled environment for sensitive measurements.

Purpose of the Study:

• To present a novel experimental setup for in situ and ex situ optical activity studies.
• To enable measurements using second-harmonic generation circular dichroism (SHG-CD) over a broad spectral range.
• To establish a method for characterizing thin chiral films and multilayers.

Main Methods:

• Development of an experimental setup for SHG-CD measurements under UHV.
• Utilizing a racemic mixture as a reference for the anisotropy factor.
• Preparation and investigation of thin films (sub-monolayer to 1.5 μm) of R- and S-enantiomers of 1,1'-Bi-2-naphthol (BINOL).
• Evaporation of BINOL onto BK7 substrates.

Main Results:

• Successful implementation of an experimental setup for SHG-CD under UHV.
• Demonstration of the utility of a racemic mixture as a reference standard.
• Characterization of the chiroptical properties of BINOL thin films and multilayers.
• Broad spectral range SHG-CD measurements were achieved.

Conclusions:

• The developed UHV-SHG-CD setup is effective for studying the optical activity of chiral thin films.
• The methodology allows for precise characterization of enantiomeric thin films.
• This technique provides a valuable tool for materials science and physical chemistry research involving chiral molecules.