Genesis of Polyatomic Molecules in Dark Clouds: CO₂ Formation on Cold Amorphous Solid Water

Area of Science:

• Astrochemistry
• Computational Chemistry
• Surface Science

Background:

• Interstellar molecule formation is key to understanding cosmic chemical evolution.
• Reactive molecular dynamics simulations offer detailed insights into reaction pathways.
• Amorphous solid water (ASW) is a relevant surface in cold molecular clouds.

Purpose of the Study:

• To investigate the formation of carbon dioxide (CO2) from carbon monoxide (CO) and oxygen (O) on ASW.
• To characterize the reaction dynamics and product stabilization at the molecular level.
• To utilize high-level potential energy surfaces for accurate simulation.

Main Methods:

• Reactive molecular dynamics simulations were employed.
• A high-level, reproducing kernel-based potential energy surface for CO2 was utilized.
• Simulations were performed under conditions relevant to cold molecular clouds.

Main Results:

• CO2 formation from CO and O(1D) on ASW was observed.
• Recombination occurred on the subnanosecond timescale.
• Internal energy redistribution led to stabilized CO2 adsorbed on ASW.
• Both CO2 and COO formation pathways were identified.

Conclusions:

• The study elucidates the molecular-level mechanism of CO2 formation on interstellar ice analogs.
• The findings contribute to understanding the chemical evolution of the universe.
• Reactive simulations with accurate potential energy surfaces are powerful tools for astrochemistry research.