Table of contents

We propose a theory of interferometric measurement of a normal Auger decay width in molecules. Molecular Auger interferometry is based on the coherent phase control of Auger dynamics in a two-colour (ω/2ω) laser field. We show that, in contrast to atoms, in oriented molecules of certain point groups (e.g. CH3F) the relative ω/2ω phase modulates the total ionisation yield. A simple analytical formula is derived for the extraction of the widths of Auger-active states from a molecular Auger interferogram, avoiding the need of either attosecond or high-resolution spectroscopy.

This work relies on complementary theoretical and experimental studies of the processes induced by ion-furan collisions. Results of the Molecular Dynamics simulations and exploration of the energy profiles combined with coincidence mass spectrometry provide complete picture of the fragmentation of furan dication.

Oscillator strengths and integral cross sections (ICSs) of HCl are of great importance for the understanding of many different aspects of atmospheric physics. Based on the generalized oscillator strengths (GOSs) of the valence-shell excitations of HCl measured by the high-energy electron scattering, the optical oscillator strengths (OOSs) have been obtained by extrapolating the GOSs to the limit of the squared momentum transfer K² → 0. Furthermore, the ICSs of the valence-shell excitations from the threshold to 5000 eV have been obtained systematically with the aid of the BE-scaling method.

In this work, visible and EUV spectra of W⁷⁺ have been measured using the high-temperature super-conducting electron-beam ion trap at the Shanghai EBIT laboratory under extremely low-energy conditions. The relevant atomic structure has been calculated by using the flexible atomic code package and the GRASP2K code. A hypothesis for the charge-state evolution of W⁷⁺ is proposed based on our results. The occurrence of W⁷⁺ ions results from indirect ionization caused by stepwise excitation between some metastable states of lower-charge-state W ions, at the nominal electron beam energy of 59 eV.

Using the complex scaling method, together with employing highly correlated Hylleraas wave functions in which all the interparticle coordinates are included, we have calculated for the first time a F-wave resonance state in the positron-helium positive ion system near the postronium (ground state) formation threshold.

A refined Resonant Ionization Spectroscopy (RIS) scheme for high resolution Laser Photodetachment Threshold Spectroscopy (LPTS). In this work the scheme is used to measure the electron affinity of cesium.

The model potential proposed by Laughlin (Phys.Rev.A 64,013406 (2001)) can give accurate bound-state energies of atoms, which is very useful in atomic physics. We determine model potential parameters for alkali metal atomic lithium (Li) by comparing the present calculated bound-state energies with both the experimental singlet energy values and quantum defect calculations.

Observations of a kilonova associated with GW170817 provide a unique opportunity to study heavy element synthesis in the universe. However, the atomic data of r-process elements are not yet complete enough to decipher the light curves and spectral features of kilonovae. We performed extended atomic calculations for singly ionized elements with Z = 59 – 64, by employing GRASP2K package. These computations are based on strategies of Nd II published in [1]. Accuracy of data is evaluated by comparing computed energy levels with the NIST database and other authors.

The dielectronic recombination of Mg-like W⁶²⁺ (3s²) ions was studied using the flexible atomic code based on the relativistic configuration interaction method with considering Breit and QED corrections. Theoretical results are compared with the experimental results from electron beam ion trap, good consistency is obtained.

Accurate atomic data of the iron group elements are of major importance in astrophysics. In the present work energy spectrum calculations are performed for 332 lowest states for Ni II ion. Energy levels are compared with NIST database recommended values. All computations were done using the general-purpose relativistic atomic structure package GRASP2018.

We present single-photon ionization Stark spectra of Sr as a function of static electric field strength and just above the saddle-point-energy. The spectra exhibit a significant number of avoided crossings between Stark resonances, superimposed on an ionization background due to the continuum excitation. The latter may be avoided by employing single- and two-photon ionization in conjunction with phase sensitive coherent control techniques. This scheme will lead to the isolation of the resonances in differential ionization cross section measurements.

The ejected-electron excitation function of the (4p⁵5s5p)⁴S_3/2 quasimetastable state in rubidium was experimentally investigated by electron-impact in the energy range from the excitation threshold at 16.64 eV to 100 eV. The obtained data at 0.12 eV energy resolution indicate the presence of negative-ion resonances just above excitation threshold. A comparison is made with the optical excitation function of the (4p⁵5s5p)⁴S_3/2 → (4p⁶5p)²P_3/2 transition (λ = 82.37 nm), measured earlier with a lower energy resolution of ≈ 1.5 eV.

Starting with simulated OCS molecular data we use two methods to propose a framework for reconstructing geometries, using Coulomb explosion imaging (CEI), for use in the production of molecular movies. The first method is a lookup table, which helps us investigate the existence and nature of multiple solutions to the geometry reconstruction problem and define regions of degeneracy in molecular structure. The second is a new method using nonlinear constrained optimization. We also use this method to investigate the uncertainty in geometry reconstructions as a function of measurement error.

The electron affinity of thallium, Tl, has been measured using tunable infrared laser photodetachment threshold spectroscopy. The relative cross section for neutral atom production following photodetachment from Tl⁻ was measured with a crossed laser-ion beam apparatus over the photon energy range 300 - 900 meV. A single s-wave threshold was observed near 320 meV due to the opening of the ground state phodetachment channel, yielding a preliminary value for the electron affinity of thallium. The present results are compared to previous experimental and theoretical results.

Generalized oscillator strengths (GOSs) of the valence-shell excitation of sulphur dioxide are of great importance for modeling the planet's atmospheric phenomena and astronomical observations, which are determined at an incident electron energy of 1.5keV in this work. The present GOSs are helpful to assign the experimental spectra and explore excitation dynamics.

CH₃NH₃PbI_3-xCl_x crystalline film composed of cuboids and polyhedral structure was prepared by dipping and withdrawing method at ambient. X-ray diffraction shows the presence of tetragonal and cubic phases having high absorption coefficient of 10⁶ m^-1. Photoluminescence study confirms shallow and deep level emissions. Temperature dependent-cathodoluminescence shows a green luminescence at 2.51 eV accompanied by weak red and ultraviolet luminescence at 80 and 300 K.

Electron-impact excitation rate coefficients of S¹⁴⁺ ions have been studied by using a relativistic flexible atomic code that can account systematically for configuration interactions. Moreover, we also considered the resonance excitation contributions to the rate coefficients. It is found that the contributions of resonance excitation on rate coefficients is very important.

The difficulties in developing the numerical Hartree-Fock programs for atoms interacting with screened Coulomb potential have been overcome. The binding energies of atoms for various screening parameters are obtained in high accuracy. C⁴⁺ ion is investigated to demonstrate the validity of our program.

The total and magnetic cross sections for K-shell electron impact excitation (EIE) of Fe²⁰⁺ have been calculated using the fully relativistic distorted-wave approach. Degrees of linear polarization of x-ray emission following EIE are presented for several stronger 2p→1s transitions, and compared with the values for the same transition lines but from dielectronic recombination process of Fe²¹⁺ in the ground state, obvious differences are found that can be employed in diagnosing the formation mechanism of corresponding x-ray lines.

The tune-out wavelength for an atom interacting with an incident laser beam is reformulated as a zero in the Rayleigh scattering cross section instead of the dynamic polarizability (or AC Stark shift). The two pictures are equivalent in lowest order, but not when higher-order retardation effects are taken into account. Detailed high-precision calculations in Hylleraas coordinates will be presented for the tune-out wavelength of helium at 413 nm near the 2 ³S – 3³ P optical transition, including D-wave retardation corrections, and compared with recent high-precision measurements.

The 4d → 3p, 4p → 3s, and 4f → 3p x-ray transitions in Ni-like tungsten ions have been studied theoretically. The Multiconfiguration Dirac–Hartree–Fock method and the large-scale relativistic Configuration Interaction and Many Body Perturbation Theory methods have been employed in order to take into account electron correlation effects on the lines wavelengths.

Anions of iridium were stored in the cryogenic storage ring, DESIREE [1, 2, 3] and investigated using laser photodetachment. The ions were stored for up to 2000 seconds and the relaxation of several metastable states were studied by selecting different photon energies. The threshold of the previously not observed ³P₂ level is located and the lifetime of this sate is found to be longer than the storage time of the ion beam. We also find that a state exists higher in energy than the previously known level with a lifetime in the range of hundreds of milliseconds.

The K-shell dielectronic (DR), trielectronic (TR), and quadruelectronic (QR) recombination have been systematically studied for highly charged B-like ions with Z=14-50 by using the FAC code. Strong configuration mixing are found that significant influence the Auger rate, and TR strengths, and leads to irregular changes of TR/DR strength ratio along B-like sequence.

Astatine is a promising candidate for targeted alpha therapy in nuclear medicine. However, due to its scarce nature, some of its fundamental properties that determine its chemical characteristics such as the electron affinity, the binding erergy of the additional electron in a negative ion, are still unknown. Here we present the method and results of the first measurement of the electron affinity of astatine, performed with the Gothenburg ANion Detector for Affinity measurements by Laser PHotodetachment (GANDALPH) at CERN-ISOLDE.

This work aims to study laser-induced lattice dynamics when there is strong electron-lattice temperature non-equilibrium for which the material properties are poorly known. The proposed experimental technique is time-resolved photoelectron spectroscopy (Tr-PES). The main challenges of such technique are the superposition of pump and probe spectra and the distortion of the probe spectra due to the interaction with pump-induced electrons, called space charge effect (SCE). We strongly reduced this effect by tuning the 100eV XUV beamline we have developed, enabling us to investigate Copper samples.

Atomic lanthanum anion La⁻ is the best candidate for laser cooling of any atomic anions by far. The previous theoretical studies showed that La⁻ has very a complicated electronic structure, which cannot be well resolved by the traditional photoelectron spectroscopy. In the present work, we used the slow-electron velocity-map imaging method in combination with an ion trap to measure the electronic structure of La⁻. The electron affinity of La is accurately determined to be 4496.97(20) cm⁻¹ or 0.557553(25) eV.

The calculations of collisional processes require an accurate description of the target. In general, the atomic structure is obtained through tedious iterations in which a variety of configurations and parameters are chosen to minimize the differences between the numerical and experimental values of the energies and the oscillator strengths. Using a Bayesian machine learning analysis through a Tree–structured Parzen Estimator, we can reproduce the experimental atomic structure with high accuracy. Results for neutral beryllium are presented.

The electron correlation effects are crucial to the two-electron one-photon transition of double K hole excited state. Appropriate correlation model was constructed to investigate this process of 11 selected He-like ions of Z from 10 to 47. Good agreement to the previous work and some new transition data were obtained.

The Hartree-Fock equations are solved using B-splines. Convergence of self-consistency iterations is achieved by turning on the electron interaction gradually. We test the ground and excited-state sets for atoms and an electron gas confined in a harmonic potential and the jellium model of alkali-metal clusters. Comparisons are made with the Thomas-Fermi approximation and dipole polarizabilities are found and compared with experiment.

We report the investigation on three-body fragmentation of CF₄³⁺ induced by 1 keV electron collision utilizing an ion momentum spectrometer. With the help of coincidence measurement for three fragment ions, the channel CF₄³⁺→F⁺+CF2++F+ is identified. By employing Dalitz plot and Newton diagram, a sequential path-way and a concerted pathway are uncovered, which are further separated by momentum correlation of two F⁺ ions. We find that the CF₄³⁺ fragmentation prefers a sequential pathway CF₄³⁺→F⁺+CF₃²⁺→F⁺+ F⁺+CF₂⁺.

A concept of a high resolution asymmetric von Hamos X-ray spectrometer for the CRYRING@ESR electron cooler is described and its characteristics obtained by ray-tracing Monte-Carlo simulations are presented. The spectrometer will be used to study the QED effects in H-like medium-Z ions by measuring the energies of X-rays from radiative recombination of highly charged ions with cooling electrons, with a ppm precision of energy determination.

The Δn=1 dielectronic, trielectronic, and quadruelectronic recombinations of Fe¹⁴+ ion are systematically studied using the flexible atomic code based on the relativistic configuration interaction method. The theoretical rate coefficients are identified and compared with the experimental measurements at heavy-ion storage ring (TSR), good agreement is obtained.

We demonstrate the results of the first ab initio investigation of the line-shape parameters for two molecular systems important for atmospheric studies: CO-N₂ and O₂-N₂. We provide the pressure broadening and shift coefficients with their speed dependencies for purely rotational lines, calculated from highly accurate potential energy surfaces with the close-coupling scheme. This is the first, fully quantum approach to the problem of determination of the spectral line shapes for the systems important for terrestrial atmospheric measurements.

The relativistic configuration interaction with core polarization method and program for the divalent systems have been developed. Based on this new program, the energy levels, transition matrix elements, static and dynamic dipole polarizabilities of He, Be, and Mg atoms have been calculated systematically.

The spectator resonant interatomic Coulombic decay (SRICD) following the 2s →5p excitation of Ne dimers has been examined experimentally and theoretically. The molecular frame angular distributions (MFADs) of the SRICD electrons depend strongly on the direction of the polarization vector of the exciting photon with respect to the molecular axis. We demonstrate that this effect is caused by the scattering of the low-energy SRICD electron on the density of the spectator electron.

The integral cross sections (ICSs) of the valence-shell excitations of carbonyl sulphide have significant applications in the astronomical observation. Based on the generalized oscillator strengths (GOSs) of these excitations measured by the high-energy electron scattering, the ICSs of the valence-shell excitations of OCS have been determined in a wide energy region from the threshold to 5 keV with the aid of the BE-scaling method.

The static and dynamic electric dipole polarizabilities of the ground state and hyperfine ground states of the ¹³³Cs have been calculated by using relativistic configuration interaction plus core polarization (RCICP) approach. The tune-out wavelengths of ground and hyperfine ground states are also determined.

Polar, non-polar and cross-shaped isomers of OCS dimer are observed and the corresponding structures are resolved using fs laser-induced Coulomb explosion. These three structures are confirmed in the simulations, and demonstrate that the dimer structures can be reconstructed from the measured momenta distributions. Our study will promote the real time imaging the evolution of molecular dimer at fs time scale after excitation and ionization.

Photodissociation processes in the visible and ultraviolet region of water-oxygen molecular complex ion, O₂⁺(H₂O), were studied by ion imaging experiments and theoretical calculations. Two fragment ions, H₂O⁺ and O₂⁺, were observed in the experiment; the former fragment ion was produced by direct dissociation after excitation, whereas the latter was generated by nonadiabatic transitions from the initially excited states to the lower electronic states.

We present the methodology of obtaining the dataset of the beyond-Voigt line-shape parameters for spectroscopic databases from fully ab initio quantum-scattering calculations. It provides not only the pressure broadening and shift coefficients, but also their speed dependencies and the complex Dicke parameter. This approach is based on the calculations of the generalized spectroscopic cross section, resulting from the close-coupling equations solved for a given scattering system. The calculations were validated on accurate experimental spectra of the helium-perturbed hydrogen molecule.

The effect of nitrogen substitution and isomerization in naphthalene under swift charged particle collision is investigated. The ratios of single ionization to capture cross-section are measured for the case of naphthalene and two of its nitrogen-containing derivatives. The propensity of HCN loss in quinoline and isoquinoline is shown to alter systematically from evaporation dominated to randomization dominated process in the case of monocation. The influence of plasmon excitation process in polycyclic aromatic nitrogen heterocycles (PANHs) is identified for the first time.

Transition metal dichalcogenides have recently attracted great interest as an important class of two-dimensional semiconductors because of their distinctive electronic, optical and catalytic properties. Here we demonstrate the first experimental study on ultrafast excited state dynamics of few-layered molybdenum disulfide under high pressure by means of broadband transient absorption spectroscopy combined with diamond anvil cell devices.

We present a novel spectral approach to deal both with bound states and with stationary continuum waves associated to collision problems. It is based on the definition of a two dimensional radial basis which replaces the combination of single particle basis sets as employed in most of the usual spectral methods. The new basis elements are externally defined as solutions of a generalized Sturmian eigenvalue equation containing the main properties of the physical problem under consideration.

We report an experimental study about the Jahn-Teller effect resulted from the ionization of the high-est occupied molecular orbital (HOMO) 1t₂ of methane. The difference of the electron momentum distributions for the Jahn-Teller splitting components reveals the strong interaction between electronic and nuclear vibrational motion.

Momentum transfer dependence behavior of the autoionization states plays an unique role in understanding the electronic correlation effect. In the present work, the 3s^-1nl autoionization states and their peak profiles of argon have been measured at different scattering angles by fast electron impact. The momentum transfer dependence behaviors of the dipole-allowed and dipole-forbidden autoionization states of argon have been elaborated.

Dissociative electron attachment (DEA) is the most efficient way to explore the structure and dynam-ics of excited states of molecular negative ions. More importantly, DEA has been shown to be a tool for chemical control. One crucial aspect of the chemical control using DEA is the functional group dependence present in this process. Here we present cases on the effect of delocalized electrons on DEA patterns observed in simple aromatic compounds.

The Coulombic explosion of multi-charged (CO)3^q+ molecular ions produced in low energy collisions with Ar⁹⁺ projectiles was investigated using recoil ion momentum spectrometry (RIMS). A preliminary analysis of the data clearly shows a dominant triangular cyclic structure. Events that may correspond to a linear chain are also observed, but the latter could as well originate from false coincidences, associated to the fragmentation of dimers. A careful analysis of this source of background is proposed to disentangle trimer fragmentation events from false coincidences.

C₃H₂ molecules are ubiquitous in the Galaxy and present important challenges in their chemistry, whether cyclic or linear, and possibly substituted with D. Obtaining theoretical rotational quenching rates by collisions with He and H₂ as projectiles is of great importance in order to get quantitative abundance estimates. It is all the more challenging that many rotational lines are excited during the collision, resulting in computationnally very heavy quantum dynamics. The quality of various approximations will be discussed, as well as the quenching rates for astrophysical applications.

The autodetachment spectrum of decaying HD⁻ and ${{\rm{D}}}_{2}^{-}$ has been recorded with a velocity-map imaging spectrometer. Coincident detection of the neutral molecule permits the selection of events occuring in the center of the spectrometer. The discrete features of the spectrum are assigned to transitions between well identified ro-vibrational levels. Energies, lifetimes and branching ratios predicted with the non-local potential framework developed for associative detachment satisfactorily reproduce the experimental results.

Spectroscopy and kinetics of energy and heat exchange in the mixture CO₂-N₂-H₂O under passing the CO₂ laser pulses is studied. To describe the energy exchange and relaxation processes in the CO₂.- N₂ - H₂O mixture, which interacts with a laser pulse, we use the modified 3-mode model of the kinetic processes New data on the resonant absorption relative coefficient α(CO₂) for the European mid-latitude atmospheric model are presented. It is also studied a chaotic behaviour of the carbon and nitrogen dioxide concentration time series (Munich & Gdansk reg.) and the low-D chaos effect is found.

We discuss the accuracy of various published ab initio calculations of highly excited Born-Oppenheimer bound and doubly excited states in diatomic molecules. We show that some of these results appear questionable and in a few cases even clearly unreliable, a fact which may also affect the prediction of collision cross sections based on such data. Our analysis uses Quantum Defect Theory scaling laws and is supported by variational R-matrix calculations. Some simple recipes are discussed, which may help users of ab initio quantum chemistry packages to assess the quality of their results.

Stark broadening theories and calculations can now be considered as mature. The fast computers allow to calculate a great number of atomic data needed for accurate spectroscopic diagnostics and modeling, such as for stellar atmospheres and envelopes, laboratory and technological plasmas, and laser equipments. Thus the access to these data via an on line database is essential. The STARK-B database is intended to meet this need. It contains calculated widths and shifts of isolated atomic lines due to electron and ion impacts. It is still under development and will be presented at the Conference.

An extension of ab initio many-electron R-matrix theory is described which is relevant both to the time-dependent description of excitation and single and double ionization of atoms in laser pulses, and to time-independent calculation of intermediate energy electron collisions where ionized states of the target atom can be excited. Corresponding general many-electron 'inner region' code modules have been developed for use in combination with existing R-matrix method codes for diverse applications with up to two electrons explicitly described by a continuum orbital basis.

Using a hypocycloidal electron spectrometer the total dissociative electron attachment cross section and the ionization cross section for D-ribose molecule were studied in the E<30 eV energy range. A clear structure near zero energy and in the 6.0-9.5 eV range is observed in the dissociative electron attachment cross section. These features appear due to the formation of negative ion fragments of the molecule. The ionization potential of the D-ribose molecule was determined at 9.74 ± 0.02 eV. In the total ionization cross section weak features are observed, which most likely due to the formation of positive ion fragments of the initial molecule.