Formation and characterization of VUV photolytically-induced (NH2)(NH3)n aggregates, 0 ≤ n ≤ 3

Abstract

The formation of amidogen radical may be an important precursor toward the formation of prebiotic molecules on the surface of ice grains in interstellar clouds. Many laboratory experiments aimed at characterizing the photolysis of ammonia. Wide shifts were observed between the solid phase and the gas phase experiments, suggesting the presence of aggregates in solid phase experiments. We attempt to characterize the formation of aggregates between amidogen radical and ammonia during the VUV irradiation of ammonia. To this end Fourier transform infrared (FTIR) spectroscopy was used in combination with the matrix isolation technique in order to characterize species formed during the photolysis of ammonia. The experimental IR spectra were compared with the theoretical frequencies obtained from post Hartree–Fock and DFT calculations for the amidogen radical and its complexes with ammonia molecules. Experimentally, the matrix isolation technique allow us to observe several bands due to the formation of (NH₂)(NH₃)_n complexes. These bands are assigned thanks to the theoretical calculations.