Table of contents

In pioneering work by Cederbaum et al an excitation mechanism was proposed that occurs only in loosely bound matter (Cederbaum et al 1997 Phys. Rev. Lett.79 4778): it turned out, that (in particular) in cases where a local Auger decay is energetically forbidden, an excited atom or molecule is able to decay in a scheme which was termed 'interatomic Coulombic decay' (or 'intermolecular Coulombic decay') (ICD). As ICD occurs, the excitation energy is released by transferring it to an atomic or molecular neighbor of the initially excited particle. As a consequence the neighboring atom or molecule is ionized as it receives the energy. A few years later the existence of ICD was confirmed experimentally (Marburger et al 2003 Phys. Rev. Lett.90 203401; Jahnke et al 2004 Phys. Rev. Lett.93 163401; Öhrwall et al 2004 Phys. Rev. Lett.93 173401) by different techniques. Since this time it has been found that ICD is not (as initially suspected) an exotic feature of van der Waals or hydrogen bonded systems, but that ICD is a very general and common feature occurring after a manifold of excitation schemes and in numerous weakly bound systems, as revealed by more than 200 publications. It was even demonstrated, that ICD can become more efficient than a local Auger decay in some system. This review will concentrate on recent experimental investigations on ICD. It will briefly introduce the phenomenon and give a short summary of the 'early years' of ICD (a detailed view on this episode of investigations can be found in the review article by U Hergenhahn with the same title (Hergenhahn 2011 J. Electron Spectrosc. Relat. Phenom.184 78)). More recent articles will be presented that investigate the relevance of ICD in biological systems and possible radiation damage of such systems due to ICD. The occurrence of ICD and ICD-like processes after different excitation schemes and in different systems is covered in the middle section: in that context the helium dimer (He₂) is a particularly interesting (and exotic) system in which ICD was detected. It was employed in several publications to elucidate the strong impact of nuclear motion on ICD and its longrange-character. The review will present these findings and their initial theoretical predictions and give insight into most recent time-resolved measurements of ICD.

Quantum physics has revolutionized our understanding of information processing and enables computational speed-ups that are unattainable using classical computers. This tutorial reviews the fundamental tools of photonic quantum information processing. The basics of theoretical quantum computing are presented and the quantum circuit model as well as measurement-based models of quantum computing are introduced. Furthermore, it is shown how these concepts can be implemented experimentally using photonic qubits, where information is encoded in the photons' polarization.

The radiative lifetime measurements using the time-resolved laser-induced fluorescence (TR-LIF) technique are reported for 34 levels of Y I between 27 824.50 and 50 254.0 cm⁻¹, among which 27 lifetimes are reported for the first time. The branching fraction (BF) measurements based on the emission spectrum of a hollow cathode lamp (HCL) were performed for 12 of these levels, and the results of 64 lines between 274.250 and 670.063 nm were obtained. By combining them with lifetime values, the transition probabilities and absolute oscillator strengths of these lines were determined. The lifetime and oscillator strength results are in general good agreement with the data by Hannaford et al (Hannaford et al 1982 ApJ261 736).

A system of two fermions with different masses and interacting by the Coulomb potential is presented in a completely covariant framework. The spin–spin interaction, including the anomalous magnetic moments of the two fermions, is added by means of a Breit term. We solve the resulting fourth order differential system by evaluating the spectrum and the eigenfunctions. The interaction vertex with an external electromagnetic field is then determined. The relativistic eigenfunctions are used to study the photon emission from a hyperfine transition and are checked for the calculation of the Lamb shift due to the electron vacuum polarization in the muonic hydrogen.

Results from large-scale theoretical cross section calculations for the total photoionization (PI) of the 4f, 5s, 5p and 6s orbitals of the neutral tungsten atom using the Dirac Coulomb R-matrix approximation (DARC: Dirac-atomic R-matrix codes) are presented. Comparisons are made with previous theoretical methods and prior experimental measurements. In previous experiments a time-resolved dual laser approach was employed for the photo-absorption of metal vapours and photo-absorption measurements on tungsten in a solid, using synchrotron radiation. The lowest ground state level of neutral tungsten is $5{{{\rm p}}^{6}}5{{{\rm d}}^{4}}6{{{\rm s}}^{2}}{{\;}^{5}}{{{\rm D}}_{J}}$, with J = 0, and requires only a single dipole matrix for PI. To make a meaningful comparison with existing experimental measurements, we statistically average the large-scale theoretical PI cross sections from the levels associated with the ground state $5{{{\rm p}}^{6}}5{{{\rm d}}^{4}}6{{{\rm s}}^{2}}{{\;}^{5}}{{{\rm D}}_{J}}$ (J = 0, 1, 2, 3, 4) levels and the $5{{{\rm d}}^{5}}6{{{\rm s}}^{\,7}}{{{\rm S}}_{3}}$ excited metastable level. As the experiments have a self-evident metastable component in their ground state measurement, averaging over the initial levels allows for a more consistent and realistic comparison to be made. In the wider context, the absence of many detailed electron-impact excitation (EIE) experiments for tungsten and its multi-charged ion stages allows current PI measurements and theory to provide a road-map for future EIE, ionization and di-electronic cross section calculations by identifying the dominant resonance structure and features across an energy range of hundreds of eV.

We have investigated the vibrational excitation and de-excitation of ${\rm N}_{2}^{+}({{X}^{2}}\Sigma _{g}^{+})$ with electrons of energy below 1 eV. Computations have been performed using the multichannel quantum defect theory with a second-order perturbative evaluation of the K reaction matrix. Assuming a Maxwellian electron-energy distribution, the corresponding rate coefficients were also determined.

We consider three-body recombination into deep dimers in a mass-imbalanced two-component atomic gas. We use an optical model where a phenomenological imaginary potential is added to the lowest adiabatic hyper-spherical potential. The consequent imaginary part of the energy eigenvalue corresponds to the decay rate or recombination probability of the three-body system. The method is formulated in details and the relevant qualitative features are discussed as functions of scattering lengths and masses. We use zero-range model in analyses of recent recombination data. The dominating scattering length is usually related to the non-equal two-body systems. We account for temperature smearing which tends to wipe out the higher-lying Efimov peaks. The range and the strength of the imaginary potential determine positions and shapes of the Efimov peaks as well as the absolute value of the recombination rate. The Efimov scaling between recombination peaks is calculated and shown to depend on both scattering lengths. Recombination is predicted to be largest for heavy–heavy–light systems. Universal properties of the optical parameters are indicated. We compare to available experiments and find in general very satisfactory agreement.

We theoretically investigate the possibility of stimulated light force deceleration and cooling of the diatomic magnesium fluoride molecular beam with near-cycling transitions in the bichromatic standing light wave of high intensity. The weighted degeneracy and force reduction factor are considered due to the behavior of the optical bichromatic force (BCF) in near-cycling transitions with internal degeneracies, and the two-level optical Bloch equations can estimate the actual behavior of the BCF. Our simulation shows that the stimulated force exceeding the spontaneous force by a factor of 2.8 can slow down the molecular beam to several m s⁻¹ within centimeter-scale distance, and this slowing mechanism can eliminate the need of compensation of Doppler shift during the longitudinal deceleration of the molecular beam.

The influence of the closed ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=3$ transition on the neighboring ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=1$ and ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=2$ open transitions of the ⁸⁷Rb D₂ line, partially resolved under Doppler broadening, is studied at different ellipticities in the Hanle configuration with longitudinal and transverse magnetic field scans. We show that a sign reversal from an electromagnetically induced transparency (EIT) resonance to an electromagnetically induced absorption (EIA) resonance occurs with an increase in ellipticity for the ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=1$ transition in a transverse field scan. This transformation is not observed for a longitudinal field scan. These observations are attributed to the higher amplitude of the EIA resonance for the ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=3$ transition in transverse field scans for elliptical polarized light. The EIA character in the Hanle transmission profile of ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=1$ and ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=2$ transitions is enhanced (weakened) when the laser beam frequency is detuned towards (away from) the ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=3$ transition. We show by computation that at higher ellipticities, a transformation from an EIT to an EIA resonance for the ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=2$ transition occurs at low frequency shifts (towards the ${{F}_{{\rm g}}}=2\to {{F}_{{\rm e}}}=3$ transition) in a transverse field scan.