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arXiv:2607.26116

Where to Find ICEC? - Screening 2442 Systems for Interparticle Coulombic Electron Capture

Fabian L. Hofmann, Elena M. Jahr, Elke Fasshauer

physics.chem-phquant-phSubmitted Jul 28, 2026• Announced Jul 29, 2026
arXivHTMLPDF

Abstract

Interparticle Coulombic Electron Capture (ICEC) provides an environment-assisted pathway for electron attachment that can compete with photorecombination. Here, we present the first comprehensive survey of ICEC in atom-atom and atom-molecule systems, screening 2442 combinations in search of promising candidates for future experimental investigation. We employ the efficient asymptotic approximation to predict ICEC cross sections and electron spectra. Intramolecular nuclear motion is included, while interparticle nuclear dynamics is neglected to permit an extensive survey. We identify several classes of atom-atom and atom-molecule systems with favourable ICEC cross sections and ICEC-to-photorecombination ratios, including halogen-halide systems and systems involving a proton and diatomic molecules such as N$_2$, O$_2$, CO, and NO. These findings point to atmospheric and astrochemical environments in which ICEC may be relevant.

Comments
12 pages, 9 figures

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Unravelling time-resolved Interparticle Coulombic Decay: From spectral formation to decay lifetimes

Alexander V. Riegel, Max K. Humm, Jan-Thore Kahle +1 more

Electronic decay processes provide a fascinating window into correlated electronic rearrangements occurring on ultrafast timescales. Following these dynamics in real time has become increasingly accessible experimentally, but extracting the underlying electronic dynamics from measured spectra requires understanding how nuclear motion shapes the observable signal. Here, we extend an analytical description of time-resolved electronic decay spectra to include dissociative nuclear dynamics and apply it to Interparticle Coulombic Decay (ICD) in the neon dimer. The resulting spectra reproduce the experimentally observed spectral shape and reveal an unexpectedly important role of interference between pathways involving different vibronic resonance states. We further establish a clear connection between the temporal build-up of the spectral structure and the nuclear wavepacket dynamics in the decaying electronic state. Most strikingly, our analytical expressions reveal that the time-dependent integrated ICD signal contains contributions proportional to both $\exp(-t/τ)$ and $\exp[-t/(2τ)]$. Nevertheless, a conventional mono-exponential fit can describe the temporal signal remarkably well while yielding a decay lifetime that differs substantially from the underlying value. Applying the theoretically derived fitting model to experimental data for the neon dimer yields an ICD lifetime $τ$ of 73 fs, rather than the previously extracted 150(50) fs, placing the experimental value within the range of previous theoretical predictions. Since the underlying temporal structure is common to electronic decay processes, our findings have implications for extracting lifetimes from time-resolved decay spectra well beyond ICD.

quant-pharXiv:2607.24597•Jul 28, 2026
Interparticle Coulombic Electron Capture (ICEC) provides an environment-assisted pathway for electron attachment that can compete with photorecombination. Here, we present the first comprehensive survey of ICEC in atom-atom and atom-molecule systems, screening 2442 combinations in search of promising candidates for future experimental investigation.
We employ the efficient asymptotic approximation to predict ICEC cross sections and electron spectra. Intramolecular nuclear motion is included, while interparticle nuclear dynamics is neglected to permit an extensive survey.
We identify several classes of atom-atom and atom-molecule systems with favourable ICEC cross sections and ICEC-to-photorecombination ratios, including halogen-halide systems and systems involving a proton and diatomic molecules such as N2_22​, O2_22​, CO, and NO. These findings point to atmospheric and astrochemical environments in which ICEC may be relevant.
We present an analytical model for intermolecular Coulombic electron capture (ICEC) which includes the internal nuclear dynamics of the molecules involved. In ICEC, an electron attaches to an atom or molecule by transferring excess energy to a neighbor, ionizing said neighbor. While previous theoretical investigations assumed fixed nuclei, recent studies indicate that relative motion between the two ICEC partners significantly influences the process. Here, we incorporate the internal nuclear motion of the molecules involved into an analytical equation of the ICEC cross section. We employ two approaches: 1. utilizing theoretical vibrationally resolved photoionization cross sections and 2. applying the Franck-Condon principle. Our theory yields electron spectra, ICEC cross sections for individual vibronic transitions, and temperature dependent cross sections. Nuclear dynamics lead to a distribution of the electronic cross section over several vibrational states and, in our model system H+ LiH, triggers dissociation of LiH during ICEC.
Interatomic coulombic electron capture is a non-local process involving the environment-assisted attachment of a free electron with implied consequences for various systems. Starting from the established numerical model of quantum confinements in a nanowire, this dissertation sets out to deduce model-independent hypotheses for future investigations of theoretical or experimental nature and develops a generalised adaptation of the model to test whether the effective-two-electron treatment suffices to successfully capture a free electron in the experimentally motivated system of a barium (II) cation engulfed in a Bose-Einstein condensate of neutral rubidium atoms. Appearing associated to differing electronic states of the confinement region, two subprocesses can contrast in spatial preferences and resonant energies. For the investigated range of parameters, the energy levels of these associated states suggest to provide a starting point for a more comprehensive description beyond the particular parameters of an individual model. A rather simple electric dipole-dipole coupled adaptation of the model is then able to successfully show environment assisted electron attachment to a barium (II) cation aided by a surrounding cloud of ultracold rubidium atoms in typical experimental conditions.
Electron capture by isolated atoms and ions proceeds by photorecombination. In this process, a species captures a free electron by emitting a photon which carries away the excess energy. It is shown here that in the presence of an environment a competing non-radiative electron capture process can take place due to long range electron correlation. In this interatomic (intermolecular) process the excess energy is transferred to neighbouring species. The asymptotic expression for the cross section of this process is derived. We demonstrate by explicit examples that under realizable conditions, the cross section of this interatomic process can clearly dominate that of photorecombination.
Thermal collisions between potassium Rydberg atoms with intermediate values of quantum number n and target molecules that capture free low-energy electrons are investigated. The velocity, binding energy, and angular distributions of heavy-Rydberg ion-pair states formed through such collisions are measured. The experimental data are analyzed with the aid of semiclassical Monte Carlo simulations to investigate the dynamics of electron attachment to a variety of target species. Multiple reaction channels involving short- and long-lived intermediates are seen for electron capture by 1,1,1-C2Cl3F3 and CBrCl3 (where dissociation of CBrCl3 intermediates involves production of Br- and Cl- ions). Electron attachment to BrCN produces long-lived BrCN-* intermediates whose dissociation results in the creation of rotationally-hot CN- anions. Electron capture by Fe(CO)5 leads to formation of Fe(CO)5-* intermediates which can fragment producing Fe(CO)4- anions, either directly or after partial redistribution of the excess energy within the intermediate has occurred. Electron transfer in Rydberg atom collisions with C2Cl4 provide no evidence of formation of long-lived C2Cl4 ions, only Cl- ions are seen. Moreover, strong Rydberg atom scattering is observed following collisions of K(12p) Rydberg states with CH3NO2. This finding is consistent with a theory which predicts that collisions between Rydberg atoms with intermediate values of n and polar molecules can lead to strong resonant quenching of Rydberg states, i.e., n and l changing, through formation of short-lived K+...CH3NO2- ion-pair states. Finally, the improvements in sensitivity to electron capture reaction dynamics that might be achieved using different Rydberg species and a crossed molecular beam are examined. Simulations are performed to demonstrate that the use of a hyperthermal helium Rydberg atomic beam and a crossed beam of target molecules such as CCl4, BrCN and CF3I can provide new insights into dissociative electron attachment reactions. The calculations show that not only can much detailed information on translational energy release distributions and intermediate lifetimes be obtained, but also on the electron radial probability density distributions in the Rydberg atoms themselves.
Potassium atoms in selected high-lying Rydberg states (n <<< 1200) are used as a tool to probe threshold behavior in electron-molecule collisions. Collisions with non-polar electron attaching molecules such as CClsb4\\sb4sb4 are dominated by electron capture in a binary interaction between the Rydberg electron and target molecule allowing the study of electron attachment at electron energies of only a few mu\\mumueV. Analysis of the data shows the cross section for electron capture is consistent with the Wigner threshold law for an inelastic s-wave process. Collisions with polar molecules can lead to Rydberg atom destruction through transfer of molecular rotational energy to the Rydberg electron. Rydberg atom data obtained with polar targets are not consistent with scattering from a static dipole. However, the data are consistent with a threshold law that takes into account a rotationally-averaged induced dipole interaction that can possibly support bound or virtual states.
Electronic decay processes provide a fascinating window into correlated electronic rearrangements occurring on ultrafast timescales. Following these dynamics in real time has become increasingly accessible experimentally, but extracting the underlying electronic dynamics from measured spectra requires understanding how nuclear motion shapes the observable signal. Here, we extend an analytical description of time-resolved electronic decay spectra to include dissociative nuclear dynamics and apply it to Interparticle Coulombic Decay (ICD) in the neon dimer. The resulting spectra reproduce the experimentally observed spectral shape and reveal an unexpectedly important role of interference between pathways involving different vibronic resonance states. We further establish a clear connection between the temporal build-up of the spectral structure and the nuclear wavepacket dynamics in the decaying electronic state. Most strikingly, our analytical expressions reveal that the time-dependent integrated ICD signal contains contributions proportional to both exp⁡(−t/τ)\exp(-t/τ)exp(−t/τ) and exp⁡[−t/(2τ)]\exp[-t/(2τ)]exp[−t/(2τ)]. Nevertheless, a conventional mono-exponential fit can describe the temporal signal remarkably well while yielding a decay lifetime that differs substantially from the underlying value. Applying the theoretically derived fitting model to experimental data for the neon dimer yields an ICD lifetime τττ of 73 fs, rather than the previously extracted 150(50) fs, placing the experimental value within the range of previous theoretical predictions. Since the underlying temporal structure is common to electronic decay processes, our findings have implications for extracting lifetimes from time-resolved decay spectra well beyond ICD.