Infrared Spectroscopic Studies of Oxygen Atom Quantum Diffusion in Solid Parahydrogen

Area of Science:

• Quantum Solid-State Physics
• Low-Temperature Chemistry
• Astrochemistry

Background:

• Atomic diffusion in noble gas matrices is well-understood for low-temperature reactions.
• Diffusion of atomic species, other than hydrogen, in quantum solids like parahydrogen remains largely unexplored.
• Previous work showed hydrogen atom diffusion in normal-hydrogen solids at 4.2 K.

Purpose of the Study:

• To investigate the diffusion of atomic oxygen (O(3P)) in solid parahydrogen (p-H2), a quantum solid.
• To explore the mobility of O(3P) atoms and their diffusion mechanisms in a quantum environment.
• To compare atomic diffusion in p-H2 with that in noble gas matrices and astronomical ices.

Main Methods:

• In situ photogeneration of O(3P) atoms via ArF laser irradiation of O2-doped p-H2.
• Monitoring the O(3P) + O2 → O3 reaction kinetics using infrared spectroscopy.
• Analyzing O3 growth curves to extract pseudo-first-order rate constants and estimate diffusion coefficients.

Main Results:

• Atomic oxygen diffusion in solid p-H2 was successfully studied.
• Reaction rates were significantly affected by p-H2 crystal morphology.
• Observed non-Arrhenius temperature dependence indicates quantum diffusion of O(3P) atoms.

Conclusions:

• O(3P) atoms exhibit quantum diffusion in solid parahydrogen.
• Parahydrogen crystal morphology plays a crucial role in atomic diffusion.
• This research provides insights into atomic diffusion relevant to astrochemistry and quantum materials.