Formation of Hydroxylamine in Low-Temperature Interstellar Model Ices

Area of Science:

• Astrochemistry
• Chemical Kinetics
• Planetary Science

Background:

• Interstellar ices are crucial for the formation of complex organic molecules.
• Galactic cosmic rays drive chemical reactions in space.
• Understanding ice chemistry informs astrobiology and the origins of life.

Purpose of the Study:

• To investigate the synthesis of molecules from irradiated ammonia-oxygen ices.
• To elucidate the formation pathways and kinetics of reaction products.
• To assess the potential for hydroxylamine formation in interstellar environments.

Main Methods:

• Irradiation of ammonia-oxygen ice mixtures with energetic electrons at 5.5 K.
• In situ monitoring using Fourier transform infrared spectroscopy.
• Analysis of desorbed products via single-photon photoionization reflectron time-of-flight mass spectrometry.
• Kinetic fitting of coupled differential equations for reaction pathways.
• Isotope-labeled experiments (ND3-O2) to confirm mechanisms.

Main Results:

• Formation of hydroxylamine (NH2OH), water (H2O), hydrogen peroxide (H2O2), nitrosyl hydride (HNO), and various nitrogen oxides (NO, N2O, NO2, N2O2, N2O3) was observed.
• Hydroxylamine likely forms via insertion of oxygen into the N-H bond of ammonia.
• Reaction rate constants were determined through kinetic modeling.
• Isotope labeling confirmed the proposed reaction mechanisms.

Conclusions:

• Electron irradiation of interstellar analogue ices efficiently produces hydroxylamine.
• This study provides evidence for a pathway to prebiotic molecule precursors in space.
• The findings contribute to understanding the chemical evolution of the interstellar medium and the potential for life's origins.