A direct liquid sampling interface for photoelectron photoion coincidence spectroscopy

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Physical Chemistry

Background:

• Probing liquid-phase reactions under vacuum conditions presents significant challenges.
• Existing methods often require complex sample preparation or are limited in scope.

Purpose of the Study:

• To introduce an effective and flexible high vacuum interface for liquid-phase photoelectron photoion coincidence (liq-PEPICO) spectroscopy.
• To enable direct sampling and analysis of ambient pressure reactions in the liquid phase.

Main Methods:

• Development of a high-temperature sheath gas-driven vaporizer to create a molecular beam from liquid aerosols.
• Utilizing vacuum ultraviolet (VUV) radiation for ionization and ion velocity map imaging for molecular beam characterization.
• Recording time-of-flight mass spectra and mass-selected threshold photoelectron spectra (ms-TPES).

Main Results:

• Optimized liq-PEPICO source parameters to improve detection sensitivity.
• Successfully recorded ms-TPES for vanillin, 4-propylguaiacol, and 4-hydroxybenzaldehyde, with new data for the latter two.
• Verified spectral features using equation-of-motion calculations for vertical ionization energies.
• Investigated aldol condensation dynamics of benzaldehyde with acetone.

Conclusions:

• The developed liq-PEPICO interface effectively probes the liquid phase at ambient pressure.
• This direct sampling approach facilitates the study of chemical reactions during synthesis.
• The technique shows promise for applications in microfluidic devices and complex reaction analysis.