Photoelectron angular distributions from liquid water: effects of electron scattering

Area of Science:

• Physical Chemistry
• Surface Science
• Atomic and Molecular Physics

Background:

• Understanding electron behavior in condensed phases is crucial for various scientific disciplines.
• Photoelectron angular distributions (PADs) provide insights into electronic structure and dynamics.
• Previous studies have explored PADs in gas-phase water, but liquid-phase data is less understood.

Purpose of the Study:

• To measure and analyze photoelectron angular distributions (PADs) for oxygen 1s ionization from liquid water.
• To investigate the anisotropy of PADs in liquid water and compare it to gas-phase behavior.
• To determine the electron probing depth in liquid water, particularly near threshold ionization.

Main Methods:

• Experimental measurement of photoelectron angular distributions (PADs).
• Ionization of water's oxygen 1s electrons using photoelectron spectroscopy.
• Analysis of PADs at various electron kinetic energies, including below 100 eV.

Main Results:

• Measured PADs from both liquid water surfaces and bulk liquid water exhibit significant anisotropy.
• This anisotropy persists even at low electron kinetic energies where elastic scattering is substantial.
• The observed PADs contradict theoretical estimates of the inelastic mean free path at low energies.

Conclusions:

• The electron probing depth in liquid water near threshold ionization is likely smaller than current theoretical models predict.
• Experimental PAD data challenges existing assumptions about electron scattering and transport in liquid water.
• This research necessitates revised theoretical approaches for electron dynamics in condensed-phase water.