Destruction of formic acid by soft X-rays in star-forming regions

Abstract

Formic acid is much more abundant in the solid state, both in interstellar ices and cometary ices, than in the interstellar gas (ice/gas ~ 10^{4}) and this point remains a puzzle. The goal of this work is to experimentally study ionization and photodissociation processes of HCOOH (formic acid), a glycine precursor molecule. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS), employing soft X-ray photons from toroidal grating monochromator TGM) beamline (200 - 310 eV). Mass spectra were obtained using photoelectron photoion coincidence (PEPICO) method. Kinetic energy distributions and abundances for each ionic fragment have been obtained from the analysis of the corresponding peak shapes in the mass spectra. Photoionization and photodissociation cross sections were also determined. Due to the large photodissociation cross section of HCOOH it is possible that in PDRs regions, just after molecules evaporation from the grain surface, formic acid molecules are almost totally destroyed by soft X-rays, justifying the observed low abundance of HCOOH in the gaseous phase. The preferential path for the glycine formation from formic acid may be through the ice phase reaction. Keywords: HCOOH; Photoionization; X-rays; Astrochemistry.

9 pages, 7 figures, 2 tables. Accepted to be printed in A&A

References in corpus (5)

• Complex molecules in the hot core of the low mass protostar NGC1333-IRAS4A
• Molecular Gas Chemistry in AGN I. The IRAM Survey of NGC1068
• The far-IR spectrum of Sagittarius B2 region: Extended molecular absorption, photodissociation and photoionization
• Embedded Star Clusters in the W51 Giant Molecular Cloud
• Detection of reactive ions in the ultracompact HII regions Mon R2 and G29.96-0.02

Cited by in corpus (11)

• Photostability of gas- and solid-phase biomolecules within dense molecular clouds due to soft X-rays
• Dissociation of the benzene molecule by UV and soft X-rays in circumstellar environment
• Photodissociation of organic molecules in star-forming regions, III. Methanol
• Production of H${}_3^{+}$ via photodissociation of organic molecules in interstellar clouds
• Processing of formic acid-containing ice by heavy and energetic cosmic ray analogues
• Destruction and multiple ionization of PAHs by X-rays in circumnuclear regions of AGNs
• Photodissociation of organic molecules in star-forming regions II: Acetic acid
• Ionisation and dissociation of cometary gaseous organic molecules by solar wind particles I: Formic Acid
• Single and Double Photoionization and Photodissociation of Toluene by Soft X-rays in Circumstellar Environment
• Survival of gas phase amino acids and nucleobases in space radiation conditions
• Electron Attachment and Electron Ionization of Helium Droplets Containing Clusters of C60 and Formic Acid