Multiphoton ionization of large water clusters

Area of Science:

• Physical Chemistry
• Spectroscopy
• Materials Science

Background:

• Water clusters are essential for understanding hydrogen bonding and the liquid water phase.
• Investigating water cluster electronic states provides insights into bulk water properties.

Purpose of the Study:

• To investigate the electronic states of water clusters of varying sizes.
• To determine if larger water clusters approximate the bulk liquid phase.

Main Methods:

• Multiphoton ionization in the UV range coupled with time-of-flight mass spectrometry.
• Laser ionization at 355 nm and 266 nm using nanosecond and picosecond lasers.
• Analysis of ion intensities and metastable fragments dependence on laser power density.

Main Results:

• A (3+1)-photon resonance-enhanced multiphoton ionization process was identified at 355 nm.
• Water clusters up to m/z 2000 Th (reflectron) and 3000 Th (linear) were detected at 355 nm, unlike at 266 nm where n>9 clusters were not observed.
• Findings for n>10 water clusters align with data for liquid water.

Conclusions:

• Water clusters above a critical size (n>10) exhibit properties similar to bulk liquid water.
• This technique allows for the study of bulk water structure using water clusters.
• Multiphoton ionization at 355 nm is effective for studying larger water clusters.