Chlorine atom diffusion and reactivity in solid parahydrogen at 1.6-4.3 K.

Area of Science:

• Quantum Solid-State Physics
• Chemical Kinetics
• Spectroscopy

Background:

• Quantum solids exhibit unique properties, including impurity delocalization at 0 K due to zero-point energy.
• Various species are mobile in solid parahydrogen (pH2) at low temperatures, but diffusion mechanisms remain unclear for some.

Purpose of the Study:

• To investigate the diffusion and reactivity of chlorine (Cl) atoms in solid pH2.
• To elucidate the diffusion mechanism of Cl atoms in solid pH2 by studying the Cl + CO reaction.
• To examine the effect of near-infrared (NIR) radiation on impurity diffusion in solid pH2.

Main Methods:

• Fourier transform infrared (FTIR) spectroscopy was employed to study the reaction kinetics.
• Infrared spectra of ClCO and OC-HCl in solid pH2 were recorded and assigned.
• Eight kinetic experiments were conducted at 4.0 K with varying initial CO concentrations.

Main Results:

• The rate constant for the Cl + CO reaction was found to be inversely proportional to CO concentration, consistent with quantum diffusion.
• Exposure to near-infrared (NIR) radiation (4200–4700 cm⁻¹) accelerated the diffusion of Cl and CO in solid pH2.
• Spectra of ClCO and OC-HCl were identified, providing insights into reaction intermediates and products.

Conclusions:

• The diffusion of Cl atoms in solid pH2 exhibits characteristics of quantum diffusion.
• NIR radiation can significantly enhance the mobility of impurities within solid pH2.
• FTIR spectroscopy is a valuable tool for studying diffusion-controlled reactions in quantum solids.