Bulk-Water Behavior of Water Clusters Studied by Isotope Effects

Area of Science:

• Physical Chemistry
• Chemical Physics
• Thermodynamics

Background:

• Understanding the behavior of water clusters is crucial for various scientific fields.
• Isotopic composition significantly influences molecular properties and interactions.

Purpose of the Study:

• To investigate the evaporative decay of mixed heavy and light water clusters.
• To analyze the scaling of branching ratios with deuterium fraction and cluster size.
• To directly observe and quantify isotopic mixing entropy in water clusters.

Main Methods:

• Experimental measurement of evaporative decay in mixed H2O, HDO, and D2O clusters.
• Analysis of branching ratios across different cluster sizes (N=9 and above).
• Comparison of experimental results with macroscopic surface values and theoretical models.

Main Results:

• Branching ratios of isotopologue molecules were found to scale with the deuterium fraction starting from N=9.
• This scaling behavior was observed across shell closing at N=21 and aligns with macroscopic surface values.
• Direct observation of isotopic mixing entropy was achieved, with energy parameters consistent with zero-point vibrational energy differences.

Conclusions:

• The study provides direct evidence of isotopic mixing entropy in water clusters.
• Observed scaling of branching ratios supports macroscopic surface behavior in mixed water clusters.
• Results offer insights into the fundamental properties of water isotopologues and their interactions.