H₂O₂ photoproduction inside H₂O and H₂O:O₂ ices at 20-140 K

Area of Science:

• Astrochemistry
• Photochemistry
• Planetary Science

Background:

• Hydrogen peroxide (H2O2) is a molecule of interest in astrophysical environments and Earth's atmosphere.
• Understanding the formation pathways of H2O2 in icy materials is crucial for astrochemical models.
• Previous studies have explored H2O2 formation, but specific data for thin ice films under UV irradiation is limited.

Purpose of the Study:

• To investigate the laboratory production of H2O2 in thin H2O and H2O:O2 ice samples.
• To determine the temperature dependence of H2O2 formation under 121.6 nm photon irradiation.
• To derive the photochemical quantum yield of H2O2 in H2O:O2 ice as a function of temperature.

Main Methods:

• Laboratory experiments involving thin ice films (50 nm thickness) of H2O and H2O:O2 mixtures.
• Irradiation of ice samples using 121.6 nm photons at various temperatures (20-140 K).
• Measurement of H2O2 production yields as a function of irradiation temperature.

Main Results:

• H2O2 formation was observed in H2O ice at temperatures below 60 K.
• In H2O:O2 ice, H2O2 was formed across a broader temperature range (20-140 K).
• The photochemical quantum yield of H2O2 was determined for H2O:O2 (9:1) ice as a function of irradiation temperature.

Conclusions:

• The study provides quantitative data on H2O2 photoproduction in relevant icy environments.
• Findings are applicable to understanding H2O2 on astrophysical water ice bodies.
• Results can inform models of H2O2 formation within Noctilucent Cloud particles in Earth's atmosphere.