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We studied N 1s−1 inner-shell processes of the free base Phthalocyanine molecule, H2Pc, in the gas-phase. This complex organic molecule contains three different nitrogen sites defined by their covalent bonds. We identify the contribution of each site in ionized, core–shell excited or relaxed electronic states by the use of different theoretical methods. In particular, we present resonant Auger spectra along with a tentative new theoretical approach based on multiconfiguration self-consistent field calculations to simulate them. These calculations may pave the road towards resonant Auger spectroscopy in complex molecules.

International audience; We studied the iron(II) phthalocyanine molecule in the gas-phase. It is a complex transition organometallic compound, for which, the characterization of its electronic ground state is still debated more than 50 years after the first published study. Here, we show that to determine its electronic ground state, one needs a large corpus of data sets and a consistent theoretical methodology to simulate them. By simulating valence and core-shell electron spectra, we determined that the ground state is a 3 E g and that the ligand-to-metal charge transfer has a large influence on the spectra.

We have developed a magnetic bottle time-of-flight electron-electron coincidence spectrometer to perform measurements on solvated molecules in a liquid micro-jet. We present here the first results obtained after ionization of the oxygen 1s inner-shell of sodium benzoate molecules and show the possibilities to filter out the electron signal arising from the liquid phase from the signal of water molecules in the gas phase. Both photoelectrons and Auger electrons spectra (unfiltered and filtered) are presented.

High-resolution K-shell photoionization cross-sections for the C-like atomic nitrogen ion (N+) are reported in the 398 eV (31.15 Å) to 450 eV (27.55 Å) energy (wavelength) range. The results were obtained from absolute ion-yield measurements using the SOLEIL synchrotron radiation facility for spectral bandpasses of 65 meV or 250 meV. In the photon energy region 398–403 eV, 1s⟶2p autoionizing resonance states dominated the cross section spectrum. Analyses of the experimental profiles yielded resonance strengths and Auger widths. In the 415–440 eV photon region 1s⟶(1s2s22p2 4P)np and 1s⟶(1s2s22p2 2P)np resonances forming well-developed Rydberg series up n=7 and&nbsp, n=8&nbsp, respectively, were identified in both the single and double ionization spectra. Theoretical photoionization cross-section calculations, performed using the R-matrix plus pseudo-states (RMPS) method and the multiconfiguration Dirac-Fock (MCDF) approach were bench marked against these high-resolution experimental results. Comparison of the state-of-the-art theoretical work with the experimental studies allowed the identification of new resonance features. Resonance strengths, energies and Auger widths (where available) are compared quantitatively with the theoretical values. Contributions from excited metastable states of the N+ ions were carefully considered throughout.

High-resolution K-shell photoionization cross-sections for the C-like atomic nitrogen ion (N+) are reported in the 398 eV (31.15 Å) to 450 eV (27.55 Å) energy (wavelength) range. The results were obtained from absolute ion-yield measurements using the SOLEIL synchrotron radiation facility for spectral bandpasses of 65 meV or 250 meV. In the photon energy region 398 eV - 403 eV, 1s⟶2p autoionizing resonance states dominated the cross section spectrum. Analyses of the experimental profiles yielded resonance strengths and Auger widths. In the 415 eV - 440 eV photon region 1s⟶1s2s22p2 4Pnp and 1s⟶1s2s22p2 2Pnp resonances forming well-developed Rydberg series up n=7 and n=8 , respectively, were identified in both the single and double ionization spectra. Theoretical photoionization cross-section calculations, performed using the R-matrix plus pseudo-states (RMPS) method and the multiconfiguration Dirac-Fock (MCDF) approach were bench marked against these high-resolution experimental results. Comparison of the state-of-the-art theoretical work with the experimental studies allowed the identification of new resonance features. Resonance strengths, energies and Auger widths (where available) are compared quantitatively with the theoretical values. Contributions from excited metastable states of the N+ ions were carefully considered throughout.

This article presents N2+ fragment yields following nitrogen K-shell photo-absorption in the NH+ molecular ion measured at the SOLEIL synchrotron radiation facility in the photon energy region 390&ndash, 450 eV. The combination of the high sensitivity of the merged-beam, multi-analysis ion apparatus (MAIA) with the high spectral resolution of the PLEIADES beamline helped to resolve experimentally vibrational structures of highly excited [N1s-1H]*+ electronic states with closed or open-shell configurations. The assignment of the observed spectral features was achieved with the help of density functional theory (DFT) and post-Hartree Fock Multiconfiguration Self-Consistent-Field/Configuration Interaction (MCSCF/CI) ab-initio theoretical calculations of the N1s core-to-valence and core-to-Rydberg excitations, including vibrational dynamics. New resonances were identified compared to previous work, owing to detailed molecular modeling of the vibrational, spin-orbit coupling and metastable state effects on the spectra. The latter are evidenced by spectral contributions from the 4- electronic state which lies 0.07 eV above the NH+ 2 ground state.

International audience; An existing cylindrical mirror analyzer (CMA) that was initially equipped with eight channeltrons detectors has been modified to install large micro-channel plate detectors to perform parallel detection of electrons on an energy range corresponding to ~12% of the mean pass energy. This analyzer is dedicated to photoelectron spectroscopy of ions ionized by synchrotron radiation. The overall detection efficiency is increased by a factor of ~20 compared to the original analyzer. A proof of principle of the efficiency of the analyzer has been done for Xe 5+ and Si + ions and will allow photoelectron spectroscopy on many other ionic species.

For an atomic state with two electrons missing from different core orbitals one may assume that the deeper hole decays first. However, it is quite probable that the double core-hole state will decay by emission of a slow Auger electron where the deeper core hole remains a spectator, especially if the outer core hole can be filled by Coster-Kronig transition, while the deeper cannot. We study here the competition of both Auger decay channels in a model system, the $1s2s2{p}^{6}(3s/3p)$ states of $\mathrm{N}{\mathrm{e}}^{+}$ ions. As the phenomenon can take place in any decay chain involving multiple core-excited states it can be critical to understand the ion yields, the electron and x-ray emission spectra, and the molecular fragmentation.

International audience; The detailed study of single photon multiple ionization processes requires the detection in coincidence of all the electrons emitted from the same ionization event. The advent of magnetic bottle experiments made possible the development of this multi-electron coincidence spectroscopy. First we will briefly review the achievements of this technique. Then we will illustrate more specifically its high sensitivity taking as an example the decay by emission of three Auger electrons of 2p and 2s holes in argon. Our results show that the processes are completely different depending on the initial core hole: the three Auger electrons are emitted dominantly in a simultaneous path for the 2p case, but in cascade for the 2s one.

Synopsis Photoionization measurements of NO+ at Nitrogen K-shell, performed at the SOLEIL Light Source will be presented. The main observed structure corresponds to the 1s to π* resonant transition.

Synopsis Single and double photoionization cross-sections in the photon region straddling the nitrogen K-edge and up to photon energies of ∼450 eV, for the atomic N+ and molecular NH+ and NH 2 + species were measured at the SOLEIL radiation facility in Orsay, France. The measurements are compared with theoretical estimates.

International audience; We report on the development and implementation of a diagnostic for the temporal characterization of ultra- short XUV pulses with a single-shot capability. The method which relies on laser-dressed photoionization in a home-made velocity map-imaging spectrometer was implemented on a HHG beamline based on a plasma mirror.

Single photon simultaneous core ionization/core excitation (K−2V) of the Benzene molecule has been observed experimentally, using synchrotron radiation, by electron coincidence spectroscopy with a magnetic bottle time-of-flight electron spectrometer and reveals a rich spectrum. DFT and Post–Hartree–Fock calculations provide detailed assignments of K−2V states. The specific Auger decay of these states has also been determined experimentally with a new technique to improve the energy resolution.

We report on complementary theoretical and laboratory investigations of the 2p ion yield cross sections for the molecular-ion series SiHn + (n = 1, 2, 3), in the 95-108 eV photon energy range, below the L-shell threshold. The experiments used an electron cyclotron resonance (ECR) plasma molecular-ion source coupled with monochromatised synchrotron radiation in a merged-beam configuration. The experimental spectra are compared with total photoabsorption cross-sectional profiles calculated using an ab initio configuration interaction method inclusive of spin-orbit coupling and the vibrational dynamics. The experimental results show vibrationally resolved resonances for SiH2 + in the 98-102 eV range. The calculations indicate twenty four core-excited states below the energy of 102 eV, of which only four contribute significantly to the observed spectrum. These states correspond to the excitation of an atomic-like 2p electron to the SiH2 + (5a1) valence orbital.

We report on complementary laboratory and theoretical investigations of the $2p$ photoexcitation cross sections for the molecular-ion series $\mathrm{Si}{{\mathrm{H}}_{n}}^{+}$ ($n=1,2,3$) near the $L$-shell threshold. The experiments used an electron cyclotron resonance (ECR) plasma molecular-ion source coupled with monochromatized synchrotron radiation in a merged-beam configuration. For all three molecular ions, the $\mathrm{S}{\mathrm{i}}^{2+}$ decay channel appeared dominant, suggesting similar electronic and nuclear relaxation patterns involving resonant Auger and dissociation processes, respectively. The total yields of the $\mathrm{S}{\mathrm{i}}^{2+}$ products were recorded and put on absolute cross-section scales by comparison with the spectrum of the $\mathrm{S}{\mathrm{i}}^{+}$ parent atomic ion. Interpretation of the experimental spectra ensued from a comparison with total photoabsorption cross-sectional profiles calculated using ab initio configuration interaction theoretical methods inclusive of vibrational dynamics and contributions from inner-shell excitations in both ground and valence-excited electronic states. The spectra, while broadly similar for all three molecular ions, moved towards lower energies as the number of screening hydrogen atoms increased from one to three. They featured a wide and shallow region below $\ensuremath{\sim}107\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$ due to $2p\ensuremath{\rightarrow}{\ensuremath{\sigma}}^{*}$ transitions to dissociative states, and intense and broadened peaks in the $\ensuremath{\sim}107--113\ensuremath{-}\mathrm{eV}$ region merging into sharp Rydberg series due to $2p\ensuremath{\rightarrow}n\ensuremath{\delta},n\ensuremath{\pi}$ transitions converging on the ${L}_{\mathrm{II},\mathrm{III}}$ limits above $\ensuremath{\sim}113\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$. This overall spectral shape is broadly replicated by theory in each case, but the level of agreement does not extend to individual resonance structures. In addition to the fundamental interest, the work should also prove useful for the understanding and modeling of astronomical and laboratory plasma sources where silicon hydride molecular species play significant roles.

International audience; Hydride molecular ions are key ingredients of the interstellar chemistry since they are precursors of more complex molecules. In regions located near a soft X-ray source these ions may resonantly absorb an X-ray photon which triggers a complex chain of reactions. In this work, we simulate ab initio the X-ray absorption spectrum, Auger decay processes and the subsequent fragmentation dynamics of two hydride molecular ions, namely CH2+ and CH3+. We show that these ions feature strong X-ray absorption resonances which relax through Auger decay within 7 fs. The doubly-charged ions thus formed mostly dissociate into smaller ionic carbon fragments: in the case of CH2+, the dominant products are either C+/H+/H or CH+/H+. For CH3+, the system breaks primary into CH2+ and H+, which provides a new route to form CH2+ near a X-ray source. Furthermore, our simulations provide the branching ratios of the final products formed after the X-ray absorption as well as their kinetic and internal energy distributions. Such data can be used in the chemistry models of the interstellar medium.

International audience

Resonant photoionization cross sections of $\mathrm{M}{\mathrm{n}}^{n+}$ ($n=5$ to 8) ions are measured in absolute values in the photon energy range of the $2p\ensuremath{\rightarrow}3d$ transitions $(645--690\phantom{\rule{0.16em}{0ex}}\mathrm{eV})$ using a merged-beams setup at the SOLEIL synchrotron radiation facility. The experimental cross sections are compared to calculations we performed using a multiconfiguration Dirac-Fock code and the opas code dedicated to radiative opacity calculations of hot and dense plasmas. Both calculations reproduce the measurements well.

The ${M}_{4,5}{N}_{2,3}{N}_{2,3}$ and ${M}_{4,5}{N}_{1}{N}_{2,3}$ Auger decay of atomic Rb have been studied by using photoelectron-Auger electron coincidence measurements that enable initial ionic state selected Auger spectroscopy. The Auger spectra in the present study are separated by the total angular momentum $j$ of the $3d$ hole and the orbital of the valence electron $n\ensuremath{\ell}$ after photoionization. It is shown that the technique allows isolating overlapping features and the study of otherwise unobservable spectral details, from which the presence of shake-down transitions during normal Auger decay is demonstrated experimentally. The technique allows also probing the effects of initial state parity and electron correlation in Auger electron spectroscopy. The observed spectral features are interpreted with theoretical predictions obtained from configuration interaction Dirac-Fock approach.

Photoionization of a buckminsterfullerene ion is investigated using an ion trap and a merged beam setup coupled to synchrotron radiation beamlines and compared to theoretical calculations. Absolute measurements derived from the ion trap experiment allow discrepancies concerning the photoionization cross section of C-60(+) to be solved.

We describe the merged-beam setup permanently installed on a dedicated optical branch of the PLEIADES beamline at SOLEIL, the French synchrotron radiation facility in St-Aubin, delivering photons in the 10–1000 eV photon energy range. The setup is designed both for photoion and photoelectron spectroscopy experiments on atomic and molecular ions. Ion spectrometry is dedicated to the determination of absolute single and multiple photoionization cross sections. Electron spectroscopy brings additional information on the non-radiative decay of inner-vacancies produced in the photoionization processes and allows for the determination of partial cross sections. Efficient reduction of the background in the electron spectra is achieved by the use of the electron-ion coincidence technique. Examples of photoion and photoelectron spectra are given for the Xe5+ ion.

Spectral probes for the ${\mathrm{CH}}^{+}, {\mathrm{OH}}^{+}$, and ${\mathrm{SiH}}^{+}$ hydride molecular ions that play key roles in astrophysics and plasma processes are presented. The merged-beam technique at the SOLEIL synchrotron was used to record the photoionization (ion yield) spectra of ${\mathrm{CH}}^{+}, {\mathrm{OH}}^{+}$, and ${\mathrm{SiH}}^{+}$ and that of their parent atomic ions, in the $K$-shell and $L$-shell regions, respectively. Energies and oscillator strengths for the $K\ensuremath{\alpha}$ (${\mathrm{CH}}^{+}$ and ${\mathrm{OH}}^{+}$) and $L\ensuremath{\alpha}$ (${\mathrm{SiH}}^{+}$) transitions were determined from the spectra. Ab initio calculations interpret the experimental data in terms of contributions from ground and excited valence electronic states.

We have studied, for the first time by electron spectroscopy, the Auger decay of the $4d\ensuremath{\rightarrow}nf$ ($n=4,5$) resonances in ${\mathrm{Xe}}^{5+}$ ion. By detecting in coincidence the Auger electrons with the resulting ${\mathrm{Xe}}^{6+}$ ions, we unravel the contribution of the different final ionic states to the total cross section measured by ion spectroscopy. A strong intensity of $5s5p$ satellite lines has been observed, up to 4 times stronger than the $5{s}^{2}$ main lines. This unexpected behavior is confirmed by multiconfiguration Dirac-Fock calculations. This technique provides the most stringent test for theoretical models and allows us to disentangle the contribution of ions in the ground and metastable states in the target beam.

In this paper, we report results on two-colour above-threshold ionisation, where extreme ultraviolet pulses of femtosecond duration were synchronised to intense infrared laser pulses of picosecond duration, in order to study the laser-assisted photoelectric effect of atomic helium, neon, krypton and xenon which leads to the appearance of characteristic sidebands in the photoelectron spectra. The observed trends are found to be well described by a simple model based on the soft-photon approximation, at least for the relatively low optical intensities of up to 5x10$^{11}$ Wcm$^{-2}$ employed in these early experiments.

High-resolution measurements for inner-shell photoionization of Na are presented along with Breit?Pauli R-matrix calculations. The results show excellent agreement, and give insight into the nature and importance of the various relativistic and correlation effects on the inner-shell process.

International audience; The post-collision interaction (PCI) distortion of the Auger electron line shapes after K 3s photoionization is revealed in coincidence measurements and confirmed by calculations.

Absolute cross sections for the single and double K-shell photoionization of carbonlike ${\mathrm{O}}^{2+}$ and nitrogenlike ${\mathrm{O}}^{+}$ ions were measured in the 526--620-eV photon energy range by employing the ion-photon merged-beam technique at the SOLEIL synchrotron radiation facility. High-resolution spectroscopy up to $E/\mathrm{\ensuremath{\Delta}}E\ensuremath{\approx}5300$ was achieved. Rich resonance structures observed in the experimental spectra are analyzed and identified with the aid of R-matrix and multiconfiguration Dirac-Fock (MCDF) methods. For these two atomic oxygen ions of particular astrophysical interest we characterized the strong $1s\ensuremath{\rightarrow}2p$ and the weaker $1s\ensuremath{\rightarrow}np\phantom{\rule{0.28em}{0ex}}(ng2)$ resonances observed. A detailed comparison of the energies of the $1s\ensuremath{\rightarrow}2p$ resonances in the first members of the oxygen isonuclear sequence measured by synchrotron based experiments and the Chandra and XMM-Newton x-ray satellites is presented.

We have studied photoionization in the inner valence $3s$ subshell of K and the spectroscopic properties of the two $3{s}^{\ensuremath{-}1}\phantom{\rule{0.28em}{0ex}}(^{1}S)$ and $(^{3}S)$ resulting states. Similar to the Rb and Cs cases, the lifetime widths of the $(^{1}S)$ and $(^{3}S)$ states are found to be markedly different, due to the electron correlation effects. The main part of the study deals with the subsequent Auger decay of the $3{s}^{\ensuremath{-}1}$ states, which have the particularity to involve low energy $(\ensuremath{\sim}5\phantom{\rule{0.16em}{0ex}}\mathrm{eV})$ Auger electrons. A magnetic bottle spectrometer with a multicoincidence technique has been used to observe and filter the Auger spectra with respect to the ${\mathrm{K}}^{2+}$ final state. The evolution of these Auger spectra has been investigated near the ionization threshold. They show strong post-collision interaction (PCI) effects, which are well reproduced by semiclassical and eikonal models. They reveal the importance of the photoelectron--Auger-electron interaction associated with these low energy Auger electrons.

Isotope effects in two-photon two-color photoionization are investigated by a combined theoretical and experimental study of the ionization of xenon atoms. A combination of variable polarization synchrotron and laser radiations are used to excite the $5{{{\rm p}}^{5}}{{(}^{2}}{{{\rm P}}_{1/2}})4{\rm f}{{[\frac{5}{2}]}_{2}}$ autoionizing resonance via the intermediate $5{{{\rm p}}^{5}}{{(}^{2}}{{{\rm P}}_{3/2}})5{\rm d}{{[\frac{3}{2}]}_{1}}$ state. Electrons and ions are detected in coincidence in order to extract the photoelectron angular distributions and the values of the linear and circular dichroism and to determine how these depend on the isotope. A complete theoretical model of the two-photon process in atoms is given in order to describe these parameters as a function of the polarization of the exciting light sources (both linear and circular polarization). Furthermore, the hyperfine depolarization due to the coupling of the electronic and nuclear angular momenta in the intermediate state is taken into account. The results of the theoretical model are in agreement with the experimental results and allow estimation of the previously unknown hyperfine structure (HFS) constant for the case of overlapping HFS levels.

Photoelectron spectra of atomic potassium excited by laser optical pumping into the 3p 6 4p 2 P1/2 and 2 P3/2 states are measured with high-energy resolution. The relative intensities of the 3p 5 4p fine-structure lines depend strongly on the initial excitation to one of the 4p spin–orbit components. Similar to the case of sodium, dynamically and quasiforbidden transitions are observed in the photoelectron spectra of potassium. The theoretical predictions of the generalized geometrical model are in excellent agreement with the experimental data.

Novel interference effects are observed in the Auger resonant Raman transitions of core-excited HF. Pronounced oscillations, controlled by detuning above the resonance maximum, appear in the spectator decay spectra of the dissociating molecule. Using predictions from the time-dependent theory of the resonant inelastic Raman scattering, these observations are explained by a favorable spatial localization of the nuclear wavepacket in the intermediate state during its creation. This phenomenon should occur whenever photoexcitation, electronic decay and nuclear dynamics have comparable time scales.

In this paper, we present the first absolute measurements for photoionization of multiply charged oxygen ions: O 2+ and O 3+ in the ground state and in several metastable states, as well as relative data for O 4+ . Multiconfiguration Dirac-Fock and relativistic R-matrix calculations were performed and are tested here by comparison with experimental results. Our experimental and new theoretical results are also compared with the earlier theoretical data obtained in the R-matrix approximation to calculate photoionization cross sections over part of the isonuclear series of multiply charged oxygen ions. Subject headings: atomic data — methods: laboratory

We present the experimental set-up developed on an undulator beam line of Super-ACO to measure on an absolute scale the photoionisation cross section of multiply-charged ions. Recent results obtained for Ba and Sm ions are presented.

We present measurements of the absolute photoionization cross section of the aluminumlike ${\mathrm{Si}}^{+}$ ion over the 94--137 eV photon energy range. The measurements were performed using the merged-beam setup on the PLEIADES beamline at the SOLEIL synchrotron radiation facility. Signals produced in the ${\mathrm{Si}}^{2+}$ and ${\mathrm{Si}}^{3+}$ photoionization channels of the $2p$ subshell of the ${\mathrm{Si}}^{+}$ ion from both the $1{s}^{2}2{s}^{2}2{p}^{6}3{s}^{2}3p{\phantom{\rule{0.16em}{0ex}}}^{2}{P}_{1/2,3/2}$ ground levels and the $1{s}^{2}2{s}^{2}2{p}^{6}3s3{p}^{2}{\phantom{\rule{0.16em}{0ex}}}^{4}P$ metastable levels were observed. Absolute cross sections were determined. Calculations of the $2p$ inner-shell photoionization cross sections were carried out using the multiconfiguration Dirac-Fock and Dirac-Coulomb R-matrix theoretical approaches and are compared with experiment.

Absolute cross sections for the {\it K}-shell photoionization of boron-like (B-like) O$^{3+}$ ions were measured by employing the ion-photon merged-beam technique at the SOLEIL synchrotron-radiation facility in Saint-Aubin, France. High-resolution spectroscopy with E/$\Delta$E $\approx$ 5000 ($\approx$ 110 meV, FWHM) was achieved with photon energy from 540 eV up to 600 eV. Several theoretical approaches, including R-Matrix, Multi-Configuration Dirac-Fock and Screening Constant by Unit Nuclear Charge were used to identify and characterize the strong 1s $\rightarrow$ 2p and the weaker 1s $\rightarrow$ 3p resonances observed in the {\it K}-shell spectra of this ion. The trend of the integrated oscillator strength and autoionisation width (natural line width) of the strong $\rm 1s \rightarrow 2p$ resonances along the first few ions of the B-like sequence is discussed., Comment: 23 pages, 5 figures, 5 tables, accepted for publication in J. Phys. B. arXiv admin note: text overlap with arXiv:1402.0519

We have measured the partial cross sections and angle-resolved energy dependence of the electrons emitted over the energy range of the triply-excited 2p3 2P hollow lithium resonance. We have also calculated the β-behaviour using the R-matrix methodology. Experimental and theoretical results are in good agreement and show deep minima in the 1s2p 1,3P ionic channels.

We have measured the angle-resolved energy dependence of the electrons emitted over the energy range of the triply excited 2s{sup 2}2p P{sup 2} lithium resonance using synchrotron radiation. We have also calculated the behavior of the angular distribution parameter {beta} using the R -matrix approximation. Experimental and theoretical results are in good agreement and show deep minima in the 1s2p P{sup 1,} {sup 3} ionic channels. The energy at which the minima occur does not coincide with the resonance energy, but is shifted towards higher energy. (c) 2000 The American Physical Society.

Photoionization of Xe4+ to Xe7+ ions was studied by combining an electron cyclotron resonance ion source with synchrotron radiation. Multiconfiguration Dirac-Fock calculations were performed to interpret the data. Many autoionization lines were measured and identified, resulting from excitation of a 4d electron into nf and np orbitals followed by Auger decay of the excited states. Continuum photoionization is negligible for the higher members of the isonuclear series.

We present new results for the doubly excited states Li+(nln´l´) of singly ionized lithium which arise from the measurements of the Auger decay of these states to Li++ ground state ions. Primary excitation of the doubly excited states is achieved by photon impact on neutral lithium atoms and therefore the experiment probes directly the double-shakeup photoionization process h+LiLi+**+e-. Detection of the individual Li+ Auger decay lines provides information on the energies and widths of many doubly excited levels of the ion, including the lowest lying (3l,3l´) state. Classifications are made using recent theoretical calculations.

Calculations of inner-shell photoionization of ${1s}^{2}2p{}^{2}{P}^{o}$ and ${1s}^{2}3p{}^{2}{P}^{o}$ Li excited states have been performed using recent developments of the R-matrix code with a 29-term target representation for incident photon energies up to 165 eV, with particular emphasis on multiple electron processes. Partial and total cross sections are given for a number of excitation processes including the lower members of 19 hollow atom resonance series. The results are compared with recent experimental measurements of the lowest ${2s2p}^{2}{}^{2}{L}^{e}$ resonance of even-parity hollow lithium states produced by photoexcitation of laser-excited lithium atoms. Experiment and theory are in excellent agreement on a relative scale. The enhancement of the shake-up process increases with initial state excitation, up to 500% over that of the ground state for ${1s}^{2}3p{}^{2}{P}^{o}.$ Good agreement is also obtained for K-shell photoionization when comparing branching ratios with available experimental results.

Within the dipole approximation and the LS-coupling limit 3p photoionization in atomic calcium is described completely by two matrix elements and one relative phase. These three parameters are extracted from experimental observables and compared with theoretical calculations (RRPA transformed to the non-relativistic limit) for photon energies around the Cooper minimum in the 3pd channel. Taking into account the intensity-borrowing model, excellent agreement between theoretical and experimental data is found.

Recent measurements of the photoionization of Na by ejection of a $3s,$ $2p,$ or $2s$ electron give branching ratios, \ensuremath{\beta} parameters, and absolute partial cross sections for a number of excitation processes, allowing one to perform the full partition of the total photoabsorption cross section into its components. In parallel, recent developments of the $R$-matrix code, together with extensive configuration and close-coupling expansions, make it possible to calculate the relevant quantities over the continuum energy range (40--140 eV) as well as in the resonant energy region corresponding to the excitation of a $2p$ or $2s$ inner-shell electron onto empty optical orbitals. A critical comparison is made of our experimental results with previous and present theoretical calculations. Valuable information is obtained for the ionization energies and relative cross sections. The main limitation in testing the validity of the various theoretical approximations is the lack of accuracy of the experimental photoabsorption cross section measured only to about 25%.

Angle-resolved Auger and valence photoelectron spectra of HCl were measured over a 14-eV-wide photon-energy range across the Cl $2p$ ionization thresholds. Auger decay spectra of dissociative core-excited states were observed to change with photon energy, reflecting a change in the rate of dissociation. Auger electron spectra at the first Rydberg states were analyzed and the evolution of the resonant Auger to the normal Auger decay distorted by postcollision interaction was examined. Valence photoionization channels were shown to resonate strongly at the photon energies of the core-to-Rydberg excitations. Angular distributions of the photo- and Auger electron lines were derived; strong fluctuations of the \ensuremath{\beta} values of the 2\ensuremath{\pi} photoline were observed at some Rydberg resonances. Anisotropy of the Auger decay at the ${\ensuremath{\sigma}}^{*}$ and Rydberg excitations was found to be different, with the latter showing uniformly negative \ensuremath{\beta} values.

Hollow lithium states photoexcited by synchrotron radiation have been studied by electron spectroscopy. Measured values of their energies and widths are found to be in excellent agreement with saddle-point calculations. The experimental energy dependence of the partial cross-sections agrees very well with R -matrix theory. This review presents a short summary of the present status of the experiments, including recent discoveries such as the observation of a doubly hollow state and several Rydberg series.