On the formation of ozone in oxygen-rich solar system ices via ionizing radiation

Abstract

The irradiation of pure molecular oxygen (O(2)) and carbon dioxide (CO(2)) ices with 5 keV H(+) and He(+) ions was investigated experimentally to simulate the chemical processing of oxygen rich planetary and interstellar surfaces by exposure to galactic cosmic ray (GCR), solar wind, and magnetospheric particles. Deposited at 12 K under ultra-high vacuum conditions (UHV), the irradiated condensates were monitored on-line and in situ in the solid-state by Fourier transform infrared spectroscopy (FTIR), revealing the formation of ozone (O(3)) in irradiated oxygen ice; and ozone, carbon monoxide (CO), and cyclic carbon trioxide (c-CO(3)) in irradiated carbon dioxide. In addition to these irradiation products, evolution of gas-phase molecular hydrogen (H(2)), atomic helium (He) and molecular oxygen (O(2)) were identified in the subliming oxygen and carbon dioxide condensates by quadrupole mass spectrometry (QMS). Temporal abundances of the oxygen and carbon dioxide precursors and the observed molecular products were compiled over the irradiation period to develop reaction schemes unfolding in the ices. These reactions were observed to be dependent on the generation of atomic oxygen (O) by the homolytic dissociation of molecular oxygen induced by electronic, S(e), and nuclear, S(n), interaction with the impinging ions. In addition, the destruction of the ozone and carbon trioxide products back to the molecular oxygen and carbon dioxide precursors was promoted over an extended period of ion bombardment. Finally, destruction and formation yields were calculated and compared between irradiation sources (including 5 keV electrons) which showed a surprising correlation between the molecular yields (∼10(-3)-10(-4) molecules eV(-1)) created by H(+) and He(+) impacts. However, energy transfer by isoenergetic, fast electrons typically generated ten times more product molecules per electron volt (∼10(-2)-10(-3) molecules eV(-1)) than exposure to the ions. Implications of these findings to Solar System chemistry are also discussed.

Oxygen diffusion and reactivity at low temperature on bare amorphous olivine-type silicate

“…Recently, ozone formation has been studied in the laboratory using supra thermal oxygen atoms generated by energetic electrons or ions. [16][17][18] Jing et al 19 also performed experiments on the formation of ozone on bare silicates, but our present work and analysis do not lead to the same conclusions. We attribute the detection of high temperature signals at mass 32 a.m.u.…”

Photosynthesis of Carbon Dioxide From Carbon Surfaces Coated With Oxygen: Implications for Interstellar Molecular Clouds and the Outer Solar System

“…Molecular oxygen is accompanied by ozone in the presence of a UV or energetic radiation environment. For instance, it has been shown that solid O 3 is produced when frozen O 2 is irradiated with energetic ions (Baragiola et al 1999;Famá et al 2002;Ennis et al 2011), electrons (Lacombe et al 1997;Sivaraman et al 2007), and UV photons (Gerakines et al 1996;. These studies are important to ascertain the possibility of observing photosensitive icy "tracers" like O 3 on interstellar grains and planetary surfaces.…”

Real-time monitoring of ozone in air using substrate-integrated hollow waveguide mid-infrared sensors

“…Within the mid-infrared band, the most pronounced band of ozone is located at 1055 cm −1 , and is associated with the ν 3 asymmetric stretching vibration33. Furthermore, a Fermi resonance band at 2100 cm −1 , associated with the ν 1 + ν 3 combination band, is evident, yet though with at least 4-times less intensity.…”