IRFEL Selective Irradiation of Amorphous Solid Water: from Dangling to Bulk Modes

Area of Science:

• Astrochemistry
• Materials Science
• Physical Chemistry

Background:

• Amorphous solid water (ASW) is prevalent in extraterrestrial environments and Earth's atmosphere.
• Understanding ASW's intermolecular forces is key to its catalytic role in molecular formation and preservation.
• Previous studies highlight the need for deeper insights into ASW's structural dynamics.

Purpose of the Study:

• To investigate the effects of mid-infrared radiation on porous amorphous solid water (pASW).
• To study the vibrational energy injection into surface and bulk modes of pASW.
• To observe structural changes in pASW upon irradiation.

Main Methods:

• Systematic exposure of pASW to mid-infrared radiation from a free-electron laser (HFML-FELIX).
• Sequential irradiation on the same ice spot to observe cumulative effects.
• Fourier transform infrared spectroscopy in reflection-absorption mode to monitor spectral modifications.

Main Results:

• Selective structural changes were observed in both the surface and bulk of pASW.
• Injected vibrational energy led to modifications in the ice structure, despite expected fast relaxation.
• Spectral modifications indicated a conversion of energy into structural alterations.

Conclusions:

• Vibrational energy injection can induce structural changes in amorphous solid water.
• ASW's H-bonded network does not fully dissipate injected vibrational energy.
• Further research is needed to quantify these effects based on ice properties.