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Published on: March 22, 2019
Infrared intensity in small ammonia and water clusters
Mikhail N Slipchenko1, Kirill E Kuyanov, Boris G Sartakov
1Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA.
The Journal of Chemical Physics
|July 11, 2006
Summary
Infrared absorption in ammonia and water clusters was measured. Hydrogen bonding significantly enhances infrared intensity, but its size dependence differs between ammonia and water clusters.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Cluster Science
Background:
- Hydrogen bonding plays a crucial role in the properties of molecular clusters.
- Understanding the size-dependent behavior of hydrogen bonds is essential for various chemical and physical processes.
Purpose of the Study:
- To measure the infrared absorption strength in small ammonia (NH3) and water (H2O) clusters.
- To investigate the size dependence of infrared intensity per hydrogen bond in these clusters.
Main Methods:
- Utilized the helium droplet technique for precise measurements.
- Analyzed the infrared absorption spectra of ammonia and water clusters as a function of cluster size.
Main Results:
- Hydrogen bonding in dimers enhances hydrogen stretching band intensity by 4x for ammonia and 3x for water.
- Ammonia clusters show size dependence close to crystal values.
- Water clusters exhibit monotonically increasing intensity with size, yet remain half that of ice in tetramers.
- Measured infrared intensities in water clusters are 2-3x lower than theoretical calculations.
Conclusions:
- The size-dependent infrared intensity of hydrogen bonds differs significantly between ammonia and water clusters.
- Discrepancies between experimental and computational results for water clusters warrant further investigation.
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