Gas-Phase Circular Dichroism Spectroscopy Using Randomized Circularly Polarized Laser Pulses.

Area of Science:

• Molecular Spectroscopy
• Physical Chemistry
• Laser Physics

Background:

• Gas-phase circular dichroism (CD) spectroscopy is difficult due to weak signals and low molecular densities.
• Pulsed lasers and molecular beams are necessary but introduce intensity fluctuations.
• These fluctuations cause artifacts, reducing the precision of measured CD values.

Purpose of the Study:

• To develop a novel CD measurement technique for gaseous molecules.
• To suppress fluctuation-induced artifacts in CD spectroscopy.
• To enhance the accuracy and reliability of gas-phase CD measurements.

Main Methods:

• Developed a CD measurement technique using randomly alternating left- and right-handed circularly polarized laser pulses (random-CP).
• Compared random-CP with conventional regularly alternating pulses (regular-CP).
• Applied the technique to resonant two-photon ionization CD and fluorescence-detected CD spectra of jet-cooled (R)-(+)-styrene oxide.

Main Results:

• Random-CP pulses effectively decouple experimental fluctuations from the CD signal.
• This strategy minimizes systematic artifacts and improves measurement precision.
• Demonstrated more rapid convergence of CD values, consistent band profiles, and suppressed offset biases compared to regular-CP.

Conclusions:

• The random-CP pulse strategy offers a robust method for gas-phase CD measurements.
• This technique significantly enhances accuracy and reliability.
• It is broadly applicable for improving CD spectroscopy of gaseous molecules.