Interatomic Coulombic Decay following Photoionization of the Helium Dimer: Observation of Vibrational Structure

TL;DR

This study observes vibrational structures in the interatomic Coulombic decay of helium dimers following photoionization, revealing detailed fragment momentum distributions and electron energy oscillations.

Contribution

It provides the first measurement of vibrational structures in ICD of helium dimers, linking vibrational wave functions to decay dynamics.

Findings

Pronounced oscillations in electron energy distribution

Vibrational structure observed in kinetic energy release

Correlation between vibrational states and decay pathways

Abstract

Using synchrotron radiation we simultaneously ionize and excite one helium atom of a helium dimer (He_2) in a shakeup process. The populated states of the dimer ion (i.e. He^[*+](n = 2; 3)-He) are found to deexcite via interatomic coulombic decay. This leads to the emission of a second electron from the neutral site and a subsequent coulomb explosion. In this letter we present a measurement of the momenta of fragments that are created during this reaction. The electron energy distribution and the kinetic energy release of the two He^+ ions show pronounced oscillations which we attribute to the structure of the vibrational wave function of the dimer ion.