Ly{\alpha} irradiation of solid-state formamide

TL;DR

This study investigates how Lyα UV photons destroy formamide ice at 12 K, revealing the destruction rates and resulting chemical products, which enhances understanding of prebiotic molecule stability in space environments.

Contribution

The paper provides experimental data on the destruction of solid formamide by Lyα photons, including cross-sections and product formation, which was previously unquantified.

Findings

UV photons cause significant formamide destruction at 12 K.

New chemical species such as HCN and CO are formed during irradiation.

UV-induced destruction is more efficient than cosmic rays but less than atomic hydrogen.

Abstract

Formamide (NH$_2$CHO), a potential prebiotic precursor, has been proposed to play an important role in the context of origin of life on our planet. It has been observed in different environments in space including the protostellar regions and comets. The abundance and stability of NH$_2$CHO in the early stages of star formation can be better understood by incorporating the formation and destruction data in the astrochemical models. We carried out an experimental investigation to study the destruction of pure NH$_2$CHO ice at 12 K by the interaction of Ly$\alpha$ (121.6 nm) photons. The UV photo destruction of NH$_2$CHO was studied using Fourier-transform infrared spectroscopy. After UV processing, the intensity of NH$_2$CHO IR bands decreases and new bands corresponding to HCN, CO, NH$_4^+$ OCN$^-$, HNCO, and CO$_2$ appeared in the spectrum. Destruction and cumulative product formation cross-sections were derived. The comparison of destruction rate derived from the cross-section in cold and dense molecular cloud for different energetic processing agents, reveals that UV photons induces an order of magnitude higher NH$_2$CHO destruction than cosmic rays, but three orders of magnitude lower than for H atoms.