Glycolaldehyde Formation via the Dimerisation of the Formyl Radical

TL;DR

This paper investigates a new, efficient mechanism for glycolaldehyde formation in star-forming regions via the barrierless dimerisation of the formyl radical, supported by quantum mechanical modeling.

Contribution

It introduces a novel formation pathway for glycolaldehyde involving HCO dimerisation on ice surfaces, expanding understanding of complex organic molecule synthesis in space.

Findings

HCO dimerisation is barrierless and rapid on ice surfaces.

The mechanism can produce observed glycolaldehyde levels with minimal CO conversion.

Efficient formation depends on the availability of the formyl radical.

Abstract

Glycolaldehyde, the simplest monosaccharide sugar, has recently been detected in low- and high-mass star-forming cores. Following on from our previous investigation into glycolaldehyde formation (Woods et al. 2012, ApJ, 750, 19), we now consider a further mechanism for the formation of glycolaldehyde that involves the dimerisation of the formyl radical, HCO. Quantum mechanical investigation of the HCO dimerisation process upon an ice surface is predicted to be barrierless and therefore fast. In an astrophysical context, we show that this mechanism can be very efficient in star-forming cores. It is limited by the availability of the formyl radical, but models suggest that only very small amounts of CO are required to be converted to HCO to meet the observational constraints.