Interatomic Coulombic decay in small helium clusters

Area of Science:

• Atomic and Molecular Physics
• Quantum Chemistry
• Cluster Science

Background:

• Interatomic Coulombic decay (ICD) is a non-radiative process where energy transfers between excited atoms, causing ionization.
• In helium clusters, ICD can occur after ionization and excitation of a single helium atom, leading to a Coulomb explosion.
• Understanding ICD dynamics in small helium clusters is crucial for interpreting experimental observations.

Purpose of the Study:

• To theoretically investigate Interatomic Coulombic decay (ICD) in small helium clusters (2-7 atoms).
• To compare theoretical findings with experimental coincidence measurements on helium clusters of varying mean sizes.
• To elucidate the influence of cluster size on ICD rates and decay dynamics.

Main Methods:

• Theoretical investigation of ICD in helium clusters ranging from 2 to 7 atoms.
• Comparison of theoretical predictions with experimental coincidence measurements.
• Analysis of kinetic-energy distributions of helium ions resulting from ICD and frustrated Coulomb explosions.

Main Results:

• ICD rates increase with cluster size due to a higher number of decay channels and reduced interatomic distances.
• A prediction for the lifetime of the excited helium dimer is provided.
• Kinetic-energy distributions reveal charge exchange processes (frustrated Coulomb explosion), which become more probable in larger clusters.

Conclusions:

• ICD is a significant decay pathway in small helium clusters, with rates strongly dependent on cluster size.
• The observed kinetic-energy distributions are characteristic of the cluster size distribution and provide insights into frustrated Coulomb explosion dynamics.
• Theoretical modeling successfully reproduces experimental findings, validating the understanding of ICD in helium clusters.