Homogeneous water nucleation in a laminar flow diffusion chamber

Area of Science:

• Physical Chemistry
• Atmospheric Science
• Thermodynamics

Background:

• Homogeneous nucleation is a fundamental process in phase transitions.
• Accurate nucleation rate data is crucial for climate modeling and understanding atmospheric aerosols.
• Existing data for water nucleation at low temperatures (240-270 K) has gaps.

Purpose of the Study:

• To experimentally measure homogeneous nucleation rates of water in a specific temperature range.
• To compare experimental results with predictions from classic nucleation theory (CNT) and an empirical correction function.
• To determine experimental critical cluster sizes and compare them with theoretical predictions.

Main Methods:

• Utilized a laminar flow diffusion chamber to measure nucleation rates.
• Employed helium as a carrier gas at ambient pressure.
• Applied the nucleation theorem and Gibbs-Thomson equation for cluster size analysis.

Main Results:

• Experimental nucleation rates ranged from 10(2) to 10(6) cm(-3) s(-1), filling a gap in existing literature.
• Classic nucleation theory showed a stronger temperature dependence than observed experimentally.
• The empirical correction function by Wolk and Strey demonstrated good agreement with experimental data.
• Experimental critical cluster sizes compared well with Gibbs-Thomson equation predictions for small clusters, but showed overestimation for larger ones.

Conclusions:

• The empirical correction function provides a more accurate representation of water nucleation rates than CNT in the studied temperature range.
• Experimental determination of critical cluster sizes offers valuable insights into nucleation mechanisms.
• The findings contribute to a better understanding of water nucleation, relevant for atmospheric and physical chemistry applications.