Interatomic coulombic decay rate in endohedral complexes

Margarita Khokhlova,Bridgette Cooper,Nikhil Bachhawat,Vitali Averbukh,Laila Bahmanpour

doi:10.1088/1361-6455/ab9f0c

Margarita Khokhlova, Bridgette Cooper + Show 3 more

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https://doi.org/10.1088/1361-6455/ab9f0c

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Abstract

Interatomic coulombic decay (ICD) in van der Waals endohedral complexes was predicted to be anomalously fast. However, the available theoretical calculations of the ICD rates in endohedral complexes only consider the equilibrium geometry, in which the encapsulated atom is located at the centre of the fullerene cage. Here we show analytically that the dominant contribution of the dipole plasmon resonance to ICD does not deviate from its equilibrium geometry value, while contributions of higher multipole plasmons to the ICD can be neglected for most atomic displacements possible for an endohedral complex at room temperature. This is in contrast to the behaviour predicted for ionic endohedral compounds. Our results show that the conclusion of the earlier works on the ultrafast character of the ICD in endohedral complexes holds generally for a wide range of geometries possible under a thermal distribution, rather than only for the equilibrium geometry.

Highlights

Intra-atomic non-radiative decay processes [1], such as Auger effect, are most commonly observed in core-ionised atoms and molecules and typically occur on the time scale of a few femtoseconds
We have shown that the rate of Interatomic coulombic decay (ICD) in van der Waals endohedral fullerene complexes is stable with respect to the deviation of the endohedral atom from the fullerene centre
Our analytical theory describes the direct contribution to the ICD width as a weighted product of multipole excitations on the fullerene, where the weights define the dependence of the width on the complex geometry

Summary

Introduction

Intra-atomic non-radiative decay processes [1], such as Auger effect, are most commonly observed in core-ionised atoms and molecules and typically occur on the time scale of a few femtoseconds. Direct experimental measurement of the ICD lifetime has been achieved for rare gas dimers [8, 23] These experimental and theoretical studies have consistently found that ICD is a fast process occurring on the timescale of about 10–100 fs, which means that it dominates the relaxation of inner-valence-ionised complexes. For greater number of neighbouring atoms and decay channels, the ICD rate is higher and the lifetime of the inner-valence vacancy is shorter. This motivates the study of ICD in complex structures such as endohedral fullerenes where the encapsulated atom or molecule interacts with about 60 nearest neighbours, maximising the ICD rate. In order to answer this question, we develop an analytical approach to the ICD rates in van der Waals endohedral fullerene complexes at non-symmetric ‘off-centre’ geometry

Theory

Results

Conclusions and outlook