Deuterium Isotope Effect on Internal Conversion of Ethylene Studied by Time-Resolved Photoelectron Spectroscopy

Area of Science:

• Chemical Physics
• Molecular Dynamics
• Spectroscopy

Background:

• Internal conversion is a key process in molecular photophysics.
• Understanding isotopic effects provides insights into reaction mechanisms.

Purpose of the Study:

• To investigate the influence of deuterium substitution on the ultrafast internal conversion of ethylene.
• To elucidate the role of hydrogen motion in the internal conversion process.

Main Methods:

• Extreme ultraviolet time-resolved photoelectron spectroscopy (TRPES).
• Ab initio multiple spawning (AIMS) calculations.

Main Results:

• Deuterium labeling increased the internal conversion timescale by approximately √2.
• This isotopic effect aligns with theoretical predictions, confirming the importance of hydrogen motion.
• A metastable species with ~9 eV electron binding energy was observed post-conversion.

Conclusions:

• Hydrogen (and by extension, deuterium) motion is crucial for the ultrafast internal conversion in ethylene.
• The observed metastable species decays independently of isotopic substitution.