Crystallization growth rates and front propagation in amorphous solid water films

Area of Science:

• Physical Chemistry
• Materials Science
• Astrochemistry

Background:

• Amorphous solid water (ASW) is prevalent in astrophysical environments.
• Understanding ice crystallization is crucial for planetary science and astrobiology.
• Previous studies have explored ASW transformations, but growth rates require further investigation.

Purpose of the Study:

• To investigate the growth rate of crystalline ice (CI) within amorphous solid water (ASW) films.
• To determine the mechanisms and kinetics of ice crystallization in ASW.
• To compare crystallization rates under different experimental conditions.

Main Methods:

• Reflection absorption infrared spectroscopy (RAIS) was employed to monitor crystallization.
• Two experimental setups were used: capped ASW films on a CI template and uncapped ASW films.
• Isothermal experiments were conducted between 140 and 150 K.

Main Results:

• Crystallization initiated immediately without an induction time.
• The extent of crystallization increased linearly with time.
• Growth rates from both capped and uncapped film experiments showed quantitative agreement.

Conclusions:

• The findings support a model where a surface crystalline layer acts as a template for downward growth in ASW films.
• This mechanism is relevant for understanding ice formation and evolution in vacuum environments.
• The study provides quantitative data on CI growth rates in ASW, aiding astrophysical ice models.