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The $LMM$ Auger spectra of krypton are measured using the photon energies $h\ensuremath{\nu}=1709$ eV, 1792 eV, 1950 eV, and 13 keV. This approach allows separating the contributions from the various core holes ${L}_{1}, {L}_{2}$, and ${L}_{3}$. Previously unobserved transitions are presented. Complementary theoretical work is performed allowing the assignment of the spectral features. The ${L}_{2,3}Y\text{\ensuremath{-}}MMY$ ($Y={M}_{4,5},{N}_{1,2,3})$ Auger transitions of ${\mathrm{Kr}}^{2+}$ formed via Coster-Kronig Auger decay of the core holes ${L}_{1}$ and ${L}_{2}$ are also investigated. These spectra comprise about 4000 and 13 000 transitions, respectively, so that only general statements on the assignment, such as the configurations involved in the transitions, can be given.

Electronic relaxation of atomic Kr below and above the $1s$ ionization threshold is investigated experimentally using hard x-ray photoelectron spectroscopy. The experimental results are interpreted with the aid of relativistic Dirac-Fock calculations. The $1s$ orbital core-hole lifetime is extracted and the satellite's structures accompanying the photoelectron main line are assigned. Auger spectra recorded below and above the $K$ edge are also investigated. In particular, the Auger cascade originating from vacancies of different origin in the $L$ shell is analyzed in great detail. Competition between radiative $KL$ versus nonradiative $KLL$ Auger emission is emphasized.

Differences in postcollision interaction (PCI) effects on Kr L_{3}M_{4,5}M_{4,5} Auger electron spectra were observed, depending on whether the initial photoionization occurred slightly above the K threshold or slightly above the L_{3} threshold. For the former, KL fluorescence emission most likely happens and then Auger processes due to the L_{3} hole follow. The time delay due to fluorescence causes a reduced shift of the Auger peak and tailing toward lower energy, since the Auger overtaking of the photoelectron happens later in time and at a location farther away from the ionic core, compared to the case for the simple one-step L_{3}M_{4,5}M_{4,5} Auger decay after L-shell photoionization. Time-dependent theory for PCI in multistep processes agrees well with experiment, illustrating the effect as an internal clock for the time-sequence of the dynamical process.

Carbon 1s photoelectron angular distributions of an iodomethane molecule were measured relative to the recoil-frame determined by the momentum correlation between I+ and CH3+ at photoelectron energies of 3, 6.1, and 12 eV. The energy dependent behavior of the recoil-frame photoelectron angular distributions is reproduced reasonably well by the time-dependent density functional theory with B-spline methods. We discuss potential applications of the fully differential photoelectron angular distribution measurements in the molecular frame to three-dimensional molecular structural determinations identifying the directions and lengths of the bonds.

International audience; Hard X-ray electron spectroscopic study of iodine 1s and 2s photoionization of iodomethane (CH3I) and trifluoroiodomethane (CF3I) molecules is presented. The experiment was carried out at the SPring-8 synchrotron radiation facility in Japan. The results are analyzed with the aid of relativistic molecular and atomic calculations. It is shown that charge redistribution within the molecule is experimentally observable even for very deep levels and is a function of the number of electron vacancies. We also show that the analysis of Auger spectra subsequent to hard X-ray photoionization can be used to provide insight into charge distribution in molecules and highlight the necessity of quantum electrodynamics corrections in the prediction of core shell binding energies in molecules that contain heavy atoms.

International audience; Xe 1s photoelectron spectra were measured at SPring-8, Japan. The core-hole lifetime broadening was found to be 9.6 eV, yielding a lifetime of ∼68 as. The amount of radiative versus nonradiative decay was assessed by recording Auger LMM spectra below and above the K edge. Below the K edge, L vacancies are produced only by direct photoionization, while above the K edge some of these vacancies are mainly produced by KL emission following 1s photoionization. Due to the dipole selection rule for x-ray emission, the dominant role of the KL relaxation process is rather directly observed.

The high-resolution absolute photoionization cross sections for Ar, Kr, Xe and N2 in the inner-shell ionization region have been measured using a multi-electrode ion chamber and monochromatized synchrotron radiation. The energy ranges of the incident photons for the target gases were as follows: Ar: 242–252 eV (2p Rydberg excitation), Kr: 1650–1770 eV (near the 2p ionization thresholds), Xe: 665–720 eV (near the 3d ionization thresholds) and 880–1010 eV (near the 3p ionization thresholds), N2: 400–425 eV (N 1s excitation and ionization). It is the first time to measure the absolute ionization cross sections of Ar, Kr, Xe and N2 over the present energy ranges with the energy resolution of over 10,000. The natural lifetime widths of 2 p 3 / 2 − 1 4 s , 2 p 3 / 2 − 1 3 d , 2 p 3 / 2 − 1 4 d and 2 p 1 / 2 − 1 4 s resonances for Ar, 3 d 5 / 2 − 1 6 p resonance for Xe, and 1 s − 1 π g * ( v ′ = 0 ) resonance for N2 have been obtained based on the cross sections determined. The ionization energies into the Ar+ ( 2 p 3 / 2 − 1 ), Ar+ ( 2 p 1 / 2 − 1 ) and Xe+ ( 3 d 5 / 2 − 1 ) ionic states are also determined using the Rydberg formula.

Photoinduced Ba L x-rays were measured, in the excitation energy range of 5.6-30 keV, by using high-brilliance undulator radiation. The obtained intensity ratios, the excitation-energy independent L beta(4)/L beta(3), L eta/L beta(1), L iota/L alpha(1,2), L beta(6)/ L alpha(1,2) and L beta(2,15)/L alpha(1,2) as well as the excitation- energy dependent L beta(1)/L alpha(1,2), L beta(3)/L alpha(1,2) and L beta(3)/L beta(1), were compared with theoretical calculations, in which the calculations were performed by applying various subsets of the L subshell fluorescence yields and Coster-Kronig yields. Deviations of the theoretical calculations from the experimental results call on improvements in theory for the emission rates. We have also surveyed the L alpha(1,2) related x-ray hypersatellite lines in the photoinduced Ba L x-ray spectrum.

We measured the relative intensities of satellite lines in the 1s core-level photoemission spectra of Ne, as a function of excitation energy, using high-brilliant soft x-ray undulator radiation. Measured excitation functions for these satellite lines were merged with the previously reported results and discussed in terms of the intra-atomic electron–electron correlations. Some results have suggested that the internal electron scattering might play an important role in characterizing the near-threshold behaviour for the 2p →np excitation process accompanying 1s photoionization. The observed intensity ratios of the satellite lines relative to the main line were analysed with the aid of the analytic Thomas model. The observed near-threshold behaviours were also compared with the simple model calculations which take account of both the sudden creation of an inner-shell vacancy and the Coulomb interaction between the ionized electron and atomic electrons. The comparison has implied that both the amplitude and the shape of the measured excitation functions cannot be satisfactorily explained by the simple model calculations. This fact may call on an improvement in the theoretical treatment in such simple model calculations.

We studied the effect of Coster?Kronig transitions between L subshells on the anisotropy of x-rays emitted from Au ions following L-shell photoionization. The angular distribution of L x-rays was measured at incident photon energies selected above the threshold energy for each subshell with a crystal spectrometer. The experimental results show that the Coster?Kronig transitions have a small influence on the anisotropy of x-ray emission. Simple model estimations for the effect of the vacancies of the M or N shells on the anisotropy of x-ray emission following the Coster?Kronig transitions were made. The calculated results also indicate a small effect.

Auger decay process following multielectron excitation accompanying F 1s photoionization of CF4 molecule has been studied in the excitation energy range between 700 and 750 eV using angle-resolved Auger electron spectroscopy. The observed spectra have shown an enhancement in the specific band, at an electron kinetic energy of ∼ 644 eV, only in the spectrum recorded at 710 eV excitation energy of horizontally polarized light. This feature is discussed in terms of the resonant Auger emission originated from the doubly excited state. The evolution of spectral shape has also exhibited the excitation energy dependence above the threshold of multiple excitation. The origin of the spectral variation is considered due to gradual growth of the satellite Auger lines originated from the multielectron excitation.

Photoelectron–photoion–photoion coincidence momentum imaging was applied to study 2p photoemission from Ar dimers. We present measurements of the kinetic energy released in fragmentation of Ar++2, angular distributions of energetic fragments, angular distributions of photoelectrons in the laboratory frame and in the molecular frame. The mean kinetic energy of fragment Ar+ ions, 2.2 eV, is larger than the value estimated from the Coulomb explosion model with the equilibrium Ar–Ar distance. No significant differences between the photoelectron angular distributions of monomers and dimers can be found in the laboratory frame. The photoelectron angular distributions of dimers in the molecular frame show a minimum for electron emission along the dimer axis at low energies (1.2 and 3.4 eV) and become isotropic at higher kinetic energies.

The alignment of Au+ ions following L3 photoionization has been studied using a high-resolution x-ray spectrometer. We observed a small anisotropy for the angular dependence of Au Lι and Lα emissions. The alignment parameter derived from the experimental results is compared with theoretical calculations by Hartree–Fock approximation and random phase approximation with exchange. The contribution to the alignment of quadrupole interaction is discussed.

The photoion yields from O+ to O2+ were measured in the 1s–2p autoionizing resonance region of the 525–540 eV photon energy range. A multiconfiguration Dirac–Fock calculation was performed to interpret the experimental data and the results show fairly good agreement with the experimental ones. Photoionization of the N-like isoelectronic sequences of O+ and Ne3+ are discussed.

The Kalpha satellite spectra arising from the correlative multielectron processes accompanying K-shell photoionization of Ca, Ti and V were measured using a broad range crystal spectrometer. Multiconfiguration Dirac-Fock calculations were performed to interpret the observed,x-ray energies and the spectral line shape., The calculations agree fairly well with the experimental results. The variation of the KalphaL(1) satellite and the Kalpha(1,2)(h) hypersatellite intensities was measured as a function, of excitation energy in the range of 8-35 keV. The KalphaL(1)/Kalpha(1,2) intensity ratio for each,element is already saturated in our energy range, and the asymptotic values of 1.58 +/- 0.08, 1.26 +/- 0.06 and 0.97 +/- 0.05% for Ca, Ti. and V were determined. By combining the present results and the previously measured values for various elements, we have found a Z(-3.5) scaling law for the KalphaL(1)/Kalpha(1,2) intensity ratio, The measured Kalpha(1,2)(h)/Kalpha(1,2) for each element, is found to increase smoothly from its onset and shows a long saturation range extending up to at least 25 keV above the threshold for Ti. The evolution of the Kalpha(1,2)(h)/Kalpha(1,2) intensity ratio is compared with the analytic Thomas model and with the theoretical calculation based on the screened hydrogenic model. (Less)

Multiply charged ions for some gaseous and metallic elements have been produced as the target for photoionization studies using synchrotron radiation. The target densities have been measured to be typically of the order of 106 ions/cm3. Characteristics of the beam transport system is described and the feasibility of photoionization experiments along the isonuclear and the isoelectronic sequences is also discussed.

Using an ion-photon merged-beam apparatus, photoion yield spectra of and from the 4d photoionization of were measured as a function of photon energy in the range 110-160 eV. The measured spectra look very similar to those from a neutral Eu target. Both and yield spectra, a broad `giant resonance' appears at 140 eV with some preceding small peaks at 131.5, 132.8 and 134.7 eV. The summit of the `giant resonance' in the spectrum is split into two peaks. This is not observed in neutral Eu photoionization.

The importance, feasibility and method for measuring the photo-ionization cross-section of multi-charged ions using the RIKEN Electron Beam Ion Source (REBIS) is discussed. Specifically the cases for the 2 s and 1 s photo-ionization of Ar14+ is explored. It is concluded that such measurements are possible today and in future (3rd generation) synchrotron radiation facilities, and will be carried out upon modifications of the apparatus. Also described, is the first test of a PHOton Beam Ion Source using REBIS. It's potential advantage over other ion sources is that in the ion production mechanism photoionization the recoil ions obtain only near thermal energies to making ion beams with very low energy spread possible.

Using a photon - ion merged-beam technique, we measured the relative yield spectra of and ions created by photoionization of ions as a function of the photon energy in the 4d ionization region. The ion production, i.e. the double-electron ionization process is found to be dominant throughout the energy range investigated. A broad structure of 4d excitation ionization around 100 eV photon energy was observed in the yield spectrum. A spectral shoulder was observed for at around 85 eV, which was absent in the photoionization of neutral Xe. Some discrete lines were observed for both the - and -yield spectra below 75 eV. The experimental spectra were analysed by a multiconfiguration Dirac - Fock calculation. The largest structure at around 100 eV is attributable to (n=6,7) two-electron transitions. The discrete lines were found to be due to , n f transitions. A serious 4f-orbital collapse is suspected in the 4 fn p two-electron excited states, whereas the collapse is moderate in the singly excited 4f-orbitals.

Using a photon-ion merged-beam apparatus, the relative photoion-yield spectra for doubly- and triply-charged ions from Xe+, Ba+ and Eu+ ions were measured in the 4d ionization region. The giant resonance peak appears for all target ions. The peak of Xe+ is broad and that of Eu+ is relatively narrow, similar to those observed in the neutral atoms. The spectrum of Xe3+ shows some structures around 87 and 93 eV. The summit of the giant resonance peak of Eu2+ is obviously split into two. These structures observed in the Xe3+ and Eu2+ spectra are not observed in the photoion spectra of the neutral targets. Some small peaks are observed in the Xe+ spectrum between 70 and 76 eV. A multi-configuration Dirac-Fock calculation reveals that these peaks are attributed to 4d-np and 4d-nf transitions. It was also found that the broad peak centered at 100 eV corresponds to shake-up resonance (4d105s25p5→4d94f5s25p4np [n=6.7]) processes. Some prominent peaks that do not appear in the neutral Ba spectrum are observed clearly in the Ba+ one. These peaks are most probably due to the 4d-nf transition followed by Auger processes.

Photoion spectrometry has been applied to determine the relative photoionization yields of Ba+ ions around the 4d ionization threshold. A ground state Ba+ ion beam was merged with monochromatized synchrotron radiation over a length of 15 cm. Counting the number of doubly and triply charged ions produced in the interaction region, we have obtained partial photoion yields as a function of photon energy. Prominent peaks due to resonance Auger processes have been observed below the threshold. A giant resonance structure above 4d threshold was seen only for the Ba3+ spectrum.

In order to study the photoionization of multiply charged ions (MCI) by synchrotron radiation, a collinear ion-photon merging-beam (MERGING) system and an electron beam ion source (EBIS) have been developed and constructed. Their main features are described including preliminary results of test experiments.

The high‐resolution absolute photoabsorption cross section with an absolute photon energy scale for Ne in the energy region of 864–872 eV (1s−1np Rydberg states) has been measured using a multi‐electrode ionization chamber and monochromatized synchrotron radiation. The natural lifetime width of Ne 1s−13p resonance state has been obtained to be 252 ± 5 meV. The Ne+ (1s−1) ionization potential is determined to be 870.16 ± 0.04 eV by using the Rydberg formula. These absolute values are supposed to be more reliable than those previously reported.

Interatomic Coulombic decay (ICD) from an Auger-final dicationic state is observed in the Ar dimer. A $2p$ inner-shell vacancy created by photoionization is replaced with $3s$ and $3p$ vacancies via intra-atomic Auger decay. The Auger-final dicationic state is subject to ICD in which one of the $3p$ electrons in the same Ar atom fills the $3s$ vacancy while one of the $3p$ electrons from the neighboring Ar atom is emitted as an ICD electron. This ICD process is unambiguously identified by electron-ion-ion coincidence spectroscopy in which the kinetic energy of the ICD electron and the kinetic energy release between ${\mathrm{Ar}}^{+}$ and ${\mathrm{Ar}}^{2+}$ are measured in coincidence.

Vibrationally resolved O 1s photoelectron angular distributions from CO{sub 2} molecules, aligned parallel and perpendicular to the electric vector of the incident light, have been measured in the 5{sigma}{sub g}* shape resonance region, with photon energies up to 2 eV above the O 1s ionization threshold, using multiple-coincidence electron-ion momentum imaging spectroscopy. The angular distributions depend on the vibrational quanta of the antisymmetric vibrations in the O 1s ionized state but do not vary significantly as a function of the photon energy across the 5{sigma}{sub g}* shape resonance.

The photoabsorption spectrum of Ne in the excitation energy region of the $[1s2s](^{3,1}S)n\mathcal{l}{n}^{\ensuremath{'}}{\mathcal{l}}^{\ensuremath{'}}$ doubly excited states has been measured using high brilliant soft x-ray undulator radiation, where square brackets indicate hole states. The observed absorption spectrum was analyzed with the aid of theoretical calculations based on the multiconfiguration Dirac-Fock (MCDF) method. The computation has revealed that the observed features are successfully assigned with several series of the resonant double excitations, such as the $[1s2s](^{3,1}S)3snp$ $(3\ensuremath{\leqslant}n\ensuremath{\leqslant}6)$ and the $[1s2s](^{3}S)3pns$ $(4\ensuremath{\leqslant}n\ensuremath{\leqslant}6)$ series. The $[1s2s]n\mathcal{l}{n}^{\ensuremath{'}}{\mathcal{l}}^{\ensuremath{'}}$ double excitation resonance leading to the lowest $[1s2s](^{3}S)3s3p$ state was analyzed using the well-known parametrized Fano profile. The energy as well as the width of the resonance for such highly correlated multiply excited state have been determined and the possible decay channels for the $[1s2s](^{3}S)3s3p$ state were also discussed.

Angular distribution of L x rays of Au and Pb following photoionization by synchrotron radiation has been measured at the incident photon energies corresponding to the energy between ${L}_{3}$ and ${L}_{2},$ between ${L}_{2}$ and ${L}_{1},$ and above ${L}_{1}$ absorption edges. No evidence of L x-ray anisotropy was observed within the experimental errors for all incident photon energies, but in the case of ${L}_{l}$ x rays an anisotropy of a few percent might be possible. The experimental results are in good agreement with the theoretical prediction.

The streaming potentials of liquid beams of aqueous NaCl, NaBr, and NaI solutions are measured using soft X-ray, He(I), and laser multiphoton ionization photoelectron spectroscopy. Gaseous molecules are ionized in the vicinity of liquid beams and the photoelectron energy shifts are measured as a function of the distance between the ionization point and the liquid beam. The streaming potentials change their polarity with concentration of electrolytes, from which the singular points of concentration eliminating the streaming potentials are determined. The streaming currents measured in air also vanish at these concentrations. The electron binding energies of liquid water and I(-), Br(-), and Cl(-) anions are revisited and determined more accurately than in previous studies.

Photoion yields from ${\mathrm{Ne}}^{+}$ to ${\mathrm{Ne}}^{2+}$ and from ${\mathrm{Ne}}^{2+}$ to ${\mathrm{Ne}}^{3+}$ were measured near the K-shell $(1s\ensuremath{-}2p)$ autoionizing resonance region in the 841--858-eV and 850--863-eV photon energy range, respectively. Measurements were performed using a photon-ion merged-beam apparatus with an electron cyclotron resonance ion source. Multiconfiguration Dirac-Fock calculations were performed to interpret the experimental results. The calculations show fairly good agreement with the experimental results. Isonuclear series for the photoionization of ${\mathrm{Ne}}^{+},$ ${\mathrm{Ne}}^{2+},$ and ${\mathrm{Ne}}^{3+}$ are discussed.

By measuring photoion‐yield spectra for Sr2+ and Sr3+ from Sr+ ions in the ground state, we have determined relative photoionization cross section of Sr+ ions in the energy range from 135–210 eV. The 3d‐ionization of charge‐selected Sr+ ions by photon‐impact was studied for the first time. The yield‐spectrum for Sr2+ has no structure, while that for Sr3+ shows prominent discrete peaks around 140 eV. For the assignment of discrete lines observed, we used a multiconfiguration Dirac‐Fock calculation code. The calculation indicates very strong s−d mixing for the observed peaks. This is understood that after the creation of 3d‐hole, the orbital energy of 4d‐orbital almost coincides with that of 5s‐orbital due to the collapse of the wavefunction.

Using a photon-ion merged-beam technique, we studied the photoionization of multiply charged Xeq+ (q = 1-3) ions in the 4d excitation region (50-140 eV). Relative yield spectra of photoions created by single (q → q + 1) and double (q → q + 2) photoionization were measured as a function of photon energy. A broad "4d giant resonance" peak with some preceding discrete peaks appears in each total ion spectrum. The intensities of discrete peaks observed at around 4d ionization threshold strongly depend on the target charge state. Those for Xe3+ target are very strong, whereas those for Xe+ are weak. Peaks due to 4d → 5p transition, which cannot occur in the neutral Xe case, has also been observed for each ion-target. The experimental spectrum for Xe+ has been analyzed by a multiconfiguration Dirac-Fock calculation. This calculation shows that results observed may be explained in terms of the correlation of valence and excited orbitals, and the effect of 4f-orbital collapse, of which the degree varies strongly with the change of the effective nuclear charge.

Inner-shell ionization of an isolated atom typically leads to Auger decay. In an environment, for example, a liquid or a van der Waals bonded system, this process will be modified, and becomes part of a complex cascade of relaxation steps. Understanding these steps is important, as they determine the production of slow electrons and singly charged radicals, the most abundant products in radiation chemistry. In this communication, we present experimental evidence for a so-far unobserved, but potentially very important step in such relaxation cascades: Multiply charged ionic states after Auger decay may partially be neutralized by electron transfer, simultaneously evoking the creation of a low-energy free electron (electron transfer-mediated decay). This process is effective even after Auger decay into the dicationic ground state. In our experiment, we observe the decay of Ne[2+] produced after Ne 1s photoionization in Ne–Kr mixed clusters., 安定なイオンが周囲の原子の電子をキャッチ＆リリース！ --X線照射による生体分子損傷の機構解明に貢献--. 京都大学プレスリリース. 2017-02-01.