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The 17th edition of the International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters, and Surfaces (MPS) was held in Sendai, Japan, from September 4–7, 2010. It was the first time that a meeting of this series of biennial conferences was hosted in a non-European country. The conference was attended by 110 researchers (90 regular participants and 20 students) from 15 different countries around the world.

The themes that the conference covered can be divided into three broad areas: lepton impact, photon impact and heavy-particle impact. A total of 43 oral presentations – including 2 plenary talks, 29 progress reports and 12 hot topics – and 87 poster presentations were held during the course of the program. Rapid progress both in experimental and theoretical techniques has led to discussions across a broad range of currently hot topics, such as many-body dynamics and electron correlation effects in excitation processes, as well as in single and multiple ionization processes for various kinds of targets including atoms, molecules, clusters, solid state and even biological systems. A snapshot of the present status of many particle spectroscopy is given in this proceedings.

The chairs of the conference gratefully acknowledge the financial support from the Morino Foundation for Molecular Science, Iwatani Naoji Foundation, Sendai Tourism and Convention Bureau, and Intelligent Cosmos Academic Foundation. They are indebted to the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, for co-hosting the conference, as well as to the international advisory board members for their extremely helpful suggestions to make the program attractive. The united effort of the local organizing committee, involving N Watanabe (Secretary), M Okunishi (Treasurer), H Fukuzawa, M Yamazaki, Y Kino, and N Kishimoto, is also gratefully acknowledged. Without the help of these institutions and individuals it would have been impossible to organize the conference. Finally, the chairs would like to express their thanks to all the participants for contributing to lively and fruitful discussions throughout the conference.

Masahiko Takahashi and Kiyoshi Ueda

International Advisory Board

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

An overview is given on recent progress on computing triple differential cross sections for electron-impact ionization of the hydrogen molecule using a time-dependent close-coupling approach. Our calculations, when averaged over all molecular orientations, are generally in very good agreement with (e,2e) measurements made on H₂, where the molecular orientation is unknown, for a range of incident energies and outgoing electron angles and energies. In this paper, we present TDCS for ionization of H₂ at specific molecular orientations. It is hoped that this study will help stimulate future measurements of TDCS from oriented H₂ at medium impact energies.

The convergent close-coupling and the time-dependent close-coupling methods are applied to the calculation of 64.6 eV electron-impact ionization of the ground state of helium resulting in two 20 eV outgoing electrons. The results of the calculations are compared with measured fully differential cross sections in various geometries. For the generally large in-plane geometries there is good agreement between the two theories and experiment. For the out-of-plane case the cross sections are generally smaller and some differences between the two calculations are evident, as well as experiment.

The (e,3-1e) four-fold differential cross sections (4DCS) are measured for the electron impact double ionization of rare gas atoms (He, Ne, Ar) in coplanar asymmetric geometry for a wide range of ejected electron energies (5 to 144 eV) and at an incident energy of about 600 – 700 eV. Though we only show here a sample of the results, all experimental angular distributions of the 4DCS are characterized by large angular shifts of the forward and backward lobes with respect to the momentum transfer direction or its opposite, respectively. This validates our previously published results [Lahmam-Bennani et al 2002 J. Phys. B: At. Mol. Opt. Phys.35 L59] which were questioned by Götz et al [2003 J. Phys. B: At. Mol. Opt. Phys.36 L77]. A qualitative, kinematical analysis is given which allows relating these shifts and the observed structures (or sub-lobes) in the cross section distributions to the second order, 'two-step 2' double ionization mechanism, which is shown to predominate over the first-order 'shake-off' and 'two-step 1' mechanisms under the present kinematics.

Double ionization of single oriented water molecules is here investigated within a theoretical approach based on the second Born approximation. The initial wave function describing the two active electrons is taken from a single-centre description previously used with success for describing the single ionization process whereas the final state wave function describing the two ejected electrons is the approximate BBK wave function. Secondary electron angular distributions for an incident energy close to 600 eV are then reported for particular kinematical conditions and compared to their first Born homologous. Strong similarities are observed in terms of maxima localization as well as identification of the main mechanisms involved in the double ionization. On the contrary, for particular kinematical conditions we demonstrate that the first-order treatment is unable to explain the observations contrary to the second-order approximation which points out pure TS2 contributions.

The single ionization of hydrogen molecules is studied theoretically as a function of the molecular alignment. Within the framework of the two-effective center model, multiple differential cross sections as a function of both electron momenta in the final channel of the reaction, and the internuclear orientation, are computed for both non-dissociative and dissociative final H⁺₂ states. Preliminary results show that the interference pattern arising from the two-center character of the molecular target changes strongly with the final state of the residual molecular ion.

The ionization of C₆₀ in gas phase has been studied by (e,2e) experiments at about 1000 eV in asymmetric kinematics and 0.6 a.u. momentum transfer. The binding energy spectrum has been compared with previous photoemission data and theoretical calculations, while the measured coincidence angular distributions corresponding to the ionization of the HOMO and HOMO-1 have been compared with calculations that account for the ionic symmetry and electronic structure of C₆₀.

We present dynamical (e, 2e) measurements for the electron impact ionization of formic acid and tetrahydrofuran molecules performed under similar kinematics. The experiments have been performed in the coplanar asymmetric geometry for a range of momentum transfers, at an incident electron energy of 250 eV and with an ejected electron energy of 10eV. The experimental results are compared with theoretical calculations carried out using the molecular 3-body distorted wave (M3DW) model.

We report the results of triple differential cross section of coplanar (e, 2e) processes on Mg (3s) atom in modified distorted wave Born approximation (DWBA). The standard DWBA formalism has been modified by including the correlation-polarization potential (which is function of electron density) and post collision interaction. We compare our computed results with the available experimental data and observe that the inclusion of polarization potential in the standard DWBA is able to improve the agreement with experimental results.

The (e,2e) spectroscopy of an atomic system at high impact energy and large momentum transfer is considered theoretically in the case of the presence of a laser field. The (e,2e) transition is supposed to take place due to electron-electron interaction. The incident electron is described by a Volkov wave. Several approximations for the three-body final state are formulated, which include the effects unaccounted by the Volkov wave Born approximation.

We present a theoretical study of single ionization of water molecules in liquid phase by impact of fast electrons in a coplanar geometry. Multiple differential cross sections are obtained through a first order model obtained within the framework of an independent electron approximation in which relaxation of the target is not taken into account. The wavefunctions for a single water molecule in the liquid phase are obtained through a Wannier orbital formalism and the ejected electron is described by means of Coulomb functions. We also present averaged calculations over all molecular orientations. A comparison with previous theoretical and experimental results, the latter corresponding to water in gaz phase, shows a good agreement. The main physical features of the reaction (such as binary and recoil peaks) present in measurements for vapor are also observed in the present theoretical predictions.

Doubly and triply differential data for single ionization of argon, neon and molecular nitrogen have been measured for positron and electron impact energies of 200, 250, and 500 eV. Ratios of triply to doubly differential ionization yields as functions of the projectile scattering angle and energy loss are compared in order to investigate differences associated with the sign of the projectile charge. For all three systems, systematic differences are observed in the relative contributions of binary interactions. These differences are shown to increase with increasing scattering angle. Nearly identical recoil intensities are found for positron and electron impact ionization of the atomic targets but not for the molecular target.

We present the electron energy loss spectra of Ar clusters as a function of cluster size ranging from 120 to 3500 atoms/cluster. The intensity of the bulk excitation peak decreases for cluster sizes larger than 500 atoms/cluster. This characteristic feature can be explained based on a simple calculation that takes into account the mean free path of the incident electrons. The present study demonstrates the promise of surface-sensitive measurements of the excitation processes of clusters.

The absolute double differential cross section (DDCS), the generalized oscillator strength distribution (GOSD), and the ionization efficiency of ammonia (NH₃) were investigated from the threshold to 40 eV under the condition of 200 and 400 eV incident electron energies and 6 and 8 degree scattering angles using electron energy-loss spectroscopy and electron- ion coincidence techniques. To determine the absolute values, we used a mixture of helium (He) and NH₃ and normalized the measured relative DDCS spectrum by the differential cross section for 2¹P excitation of He. Our results are in close agreement with previous dipole (e, e) spectroscopy, although the incident electron energy is lower. The ionization efficiency curve obtained from coincidence measurements indicated the existence of doubly excited states that cause neutral dissociation.

Relative elastic differential cross sections for elastic scattering from cytosine and thymine have been measured using the crossed-beam method. The measurements have been performed at two electron energies of 500 and 100 eV, and cover the angular range of 10°-130°. Calculations of elastic differential cross sections have been performed via the screen corrected additivity rule method, and agreement is quite good with the present experimental results. The results obtained are important for the modelling of energy deposition in living tissue.

Spin-effects were studied in the (e,2e) scattering from W(110) single crystal and thin gold layer on W(110). Intensity asymmetry observed in the spectra using spin-polarised incident beam were identified as spin-orbit interaction in the valence electron states involved in the scattering with the contribution of orbital momentum of incident electrons.

The Si-L₂₃VV Auger electron Si-2p photoelectron coincidence spectra (Si-L₂₃VV-Si-2p APECS) of a hydrogenated Si(111)-1×1 surface are measured with an analyzer that is used for electron-electron and electron-ion coincidence measurements of surfaces. The Si-L₂₃VV-Si-2p APECS show a sharp peak, a small shoulder, and a broad large peak at electron kinetic energies of about 85, about 80.5, and about 70 eV, respectively. The clarity of the last two peaks is lower in the Si-L₂₃VV-Si-2p APECS of a clean Si(111)-7×7 surface. We attribute the three peaks to the Si-L₂₃V_3pV_3p, Si-L₂₃V_3pV_3s, and Si-L₂₃V_3sV_3s Auger lines, respectively. The three-peak structure indicates that the local density of states of the 3s + 3p band is reduced in the case of the hydrogenated Si(111)-1×1 surface. This finding is consistent with that of a previous study on valence electronic states of hydrogenated Si(111) using ultraviolet photoemission spectroscopy.

We study elastic scattering and impact ionization by returning electrons induced in a strong laser field based on the recently developed quantitative rescattering theory. The high-energy angle-resolved photoelectron spectra of molecules in strong fields are attributed to elastic scattering of the returning electrons with the parent ion. We demonstrate that the high-energy photoelectron spectra can be used to retrieve the position of atoms in a molecule. We also investigate the nonsequential double ionization of an atom in intense laser fields which is partly due to the impact ionization of the parent ion by the returning electron.

We proposed recently a theoretical method to study the infrared (IR) laser assisted photoabsorption cross sections over a broad energy range by a single calculation. We apply this method to study the IR laser assisted photoabsorption of Ne atoms near the first ionization threshold. The simulation results show that the IR field modifies the photoabsorption cross sections and the energy structures. This photoabsorption cross section is an important quantity to analyze the IR-laser assisted dynamical processes by an attosecond pulse, a pulse train or a free electron laser.

Sequential multiple photoionization of the prototypical molecule N₂ is studied with femtosecond time resolution using the Linac Coherent Light Source (LCLS). A detailed picture of intense x-ray induced ionization and dissociation dynamics is revealed, including a molecular mechanism of frustrated absorption that suppresses the formation of high charge states at short pulse durations. The inverse scaling of the average target charge state with x-ray peak brightness has possible implications for single pulse imaging applications. Moreover, we investigate the creation of double K-shell holes in N₂ molecules via sequential absorption of two photons on a timescale shorter than the core-hole lifetime by using intense x-ray pulses from the LCLS. The production and decay of these states is characterized by photoelectron spectroscopy and Auger electron spectroscopy. In molecules, two types of double core holes are expected, the first with two core holes on the same N atom, and the second with one core hole on each N atom. We report the first direct observations of the former type of core hole in a molecule, in good agreement with theory, and provide an experimental upper bound for the relative contribution of the latter type.

A new developed velocity map imaging spectrometer has been used to study the photoionization of atoms near threshold. The application of the spectrometer to the measurement of the angular distributions of the photoelectrons emitted in the photoionization of the Ne 2p_3∕2 state between the 2p spin orbit thresholds and of polarised Ne atoms are presented.

Ion yield spectra produced by the photoionization of perfluorocyclobutane (c-C₄F₈) and cis-1,1,2,2,3,4-hexafluorocyclobutane (cis-c-C₄H₂F₆) have been measured in the photon energy range of 25-170 eV. For the c-C₄F₈ photoionization, the C₃F₅⁺ and C₂F₄⁺ fragments are most abundant at all the energies, but the yields decline with the energy, giving at 170 eV about 30% of the yields at 30 e V. The C₃H₂F₃⁺ and C₂HF₃⁺ ions are the most dominant fragments for the cis-c-C₄H₂F₆ photoionization, with their yield curves similar to the C₃F₅⁺ and C₂F₄⁺ counterparts for c-C₄F₈, respectively. Photoelectron–photoion–photoion coincidence spectra were also acquired to study the breakdown pathways.

Site-dependent C1s-core excitation spectra of small acetaldehyde (AAL) clusters have been studied under the cluster regime of beam conditions. The excitation spectra of the clusters were generated by monitoring the partial-ion-yields of cluster-origin fragments. Comparison of the cluster bands with the monomer bands revealed that the band intensities of C1s core-to-Rydberg transitions come to be strongly excitation-site dependent upon cluster formation showing significant reduction of C1s_HCO→Ryd bands relative to the monomer bands. Computer modeling of X-ray absorption spectra using a density functional theory calculation demonstrated that the intensity reduction is the outcome of the site- and geometry-specific CH...O interaction where hydrogen-bonding association between the aldehyde (HCO) sites of different AAL molecules takes place exclusively within the clusters. As the representatives of small AAL clusters (n≥3), two types of molecular complexes (a planar cyclic trimer and a tetramer with a stack of two dimers) were derived to rationalize the site-dependence of the experimental C1s excitation spectra. Spectral simulation of the above complexes could reproduce the experimental site-dependence of the core-to-Rydberg band-features upon clusterization, indicative of significant contribution of these clusters under the present beam-stagnation condition.

The emission of low-energy and Auger electrons from H₂O has been investigated following photo-excitation/ionization at photon excitation energies just below and just above the O 1s ionization threshold. It is found that neutral oxygen atoms in high Rydberg states are formed. Direct evidence of post-collision interaction (PCI) between the Auger electron and the photo-electron is observed. The initially-excited electron is captured into a Rydberg orbital of H₂O⁺ and remains associated with the oxygen fragment even after the cleavage of both O-H bonds. This implies that the Rydberg states are stable, with the electron behaving as a spectator during the dissociation of H₂O⁺.

The O 1s and N 1s excited states of N₂O (nitrous oxide, N_t-N_c-O) have been investigated by the symmetry-adapted cluster–configuration interaction (SAC–CI) method. Our approach in this series of works using high-resolution angle-resolved ion-yield (ARIY) spectroscopy and the SAC-CI method is reviewed for the O 1s excited states of N₂O. The vibrational structure observed by ARIY spectroscopy was interpreted by two-dimensional ab initio potential energy surfaces (2D PESs). The valence–Rydberg coupling was analyzed by the electronic part of the second moment, <r²>. The thermal effect in the core-electron excitation spectrum was examined by the PES calculations in the bending coordinate. The 2D PESs of the N_t and N_c excited states have also been calculated by the SAC–CI method and are discussed in detail.

We analyze theoretically interference effects in the spectra of electrons emitted in the H₂ photoionization by high energy linearly polarized photons. Molecular bound and continuum states are accurately described by means of B-spline basis allowing the inclusion of the nuclear degrees of freedom. One interesting feature is observed: the usual Franck-Condon behavior is not followed when the H₂ internuclear axis is parallel to the polarization direction. Moreover, this is related to the fact that for this molecular orientation and under certain conditions, the electron cannot be emitted in the direction of the radiation field. On the contrary, for H₂ molecules perpendicular to the polarization direction, the angular distribution of electrons is analogous to the one observed in the two slits Young's experiment.

The presence of interference patterns in the spectra of emitted electrons from HeH⁺ molecular ions due to the impact of bare ions is analysed. It is shown that these oscillations, which are explained in terms of the coherent emission of electrons from the vicinities of the target nuclei, are preserved even after averaging over all molecular orientations. The influence of partial localization of electrons around the alpha particle center is studied. The relationship between electron ionization by ion impact and photoionization is investigated.

We investigated molecular fragmentation for CO, C₂H₂ and C₆₀ molecules induced by impact of various fast heavy ions. Fragment ions produced in electron capture and loss collisions of projectile ions were measured in coincidence with final projectile charge states. As for C₆₀ target, the number distribution of secondary electrons emitted in single collision event were also measured by means of a triple coincident method. The charge state distribution of transiently formed C^r+₆₀ was successfully reproduced by our new model calculation on the basis of statistical energy deposition model developed for polyatomic molecules. Data acquisition using position sensitive detection system allows us to obtain 3D momentum imaging of fragment ions from CO and C₂H₂ molecules. Typical results relevant to molecular orientation effect and kinetic energy release (KER) are discussed.

Single ionization of helium by proton impact is investigated in terms of a four-body distorted wave model. In this approximation both electrons are considered as active, being one of them ionized whereas the other remains in a residual target bound state. The influence of dynamic correlation between electrons is investigated by comparison with a four-body uncorrelated distorted wave model. Double differential cross sections as a function of the emission angle for fixed electron energies and different collision energies are presented.