A New "Non-energetic" Route to Complex Organic Molecules in Astrophysical Environments: The C + H$_2$O $\rightarrow$ H$_2$CO Solid-state Reaction

TL;DR

This study demonstrates a rapid, non-energetic solid-state reaction between carbon atoms and water ice at low temperatures, producing formaldehyde via quantum tunneling, suggesting a new pathway for complex organic molecule formation in space.

Contribution

It reveals a novel non-energetic, quantum tunneling-driven route to formaldehyde formation in astrophysical ices, independent of energetic processing.

Findings

The C + H2O reaction proceeds rapidly at low temperatures without energetic triggers.

UV irradiation mainly destroys H2CO and produces CO2, challenging previous assumptions.

The reaction provides a new pathway for prebiotic molecule synthesis in space environments.

Abstract

The solid-state reaction C + H$_2$O $\rightarrow$ H$_2$CO was studied experimentally following the codeposition of C atoms and H$_2$O molecules at low temperatures. In spite of the reaction barrier and absence of energetic triggering, the reaction proceeds fast on the experimental timescale pointing to its quantum tunneling mechanism. This route to formaldehyde shows a new "non-energetic" pathway to complex organic and prebiotic molecules in astrophysical environments. Energetic processing of the produced ice by UV irradiation leads mainly to the destruction of H$_2$CO and the formation of CO$_2$ challenging the role of energetic processing in the synthesis of complex organic molecules under astrophysically relevant conditions.