R. Bruch

Cross sections for the ionization-excitation of helium by fast electrons and H+, H2+ and H3+ ions: (np) 2P0 levels, n=2-5

Cross sections for the ionization-excitation of helium following electron and H+, H2+ and H3+ ion impact have been measured for He II (np) 2P0 states with n=2-5. These measurements were performed for the velocity range from 3.8-8.5 au for electrons, 1.4-7.5 au for protons and 1.4-4.0 au for H2+ and H3+ ions. The cross sections have been obtained by measuring the extreme ultraviolet (EUV) emission from the decay of the excited target atoms at 90 degrees to the projectile beam. We have compared our results to the current limited literature for He II (2p) 2P0 cross sections with good agreement observed. We have also examined the cross section ratio of ionization-excitation to excitation, sigma +*((np)2P0)/ sigma *((1snp)1P0), for electron and proton impact in comparison with the ratio of double to single ionization, sigma ++/ sigma +, as a limiting value for large n. Finally, cross section results from Hn+ impact, where n=1-3, are discussed in terms of a semiempirical scaling relation for molecular hydrogen projectiles.

Triply Excited States of the Lithium Isoelectronic Sequence: Z=3?54

The excitation energies and the probabilities for radiative and radiationless decays of hollow atom states belonging to the 2s22p, 2s2p2 and 2p3 configurations have been calculated on the basis of perturbation theory method (1/Z-expansion) in a broad range of values of atomic number Z. Our results agree well with the first observation of these states and the theoretical and experimental results obtained recently for neutral Li atoms. It should be noted that the 1/Z expansion method gives more accurate results for ions than for neutral systems, because of the limited number of coefficients of 1/Z expansion calculated in this work. In this case the good agreement provided by our results for neutral system allows us to believe that our data for the same triply excited states with Z>3 should be used for prediction of new experiments with these states.

Relative intensity of dielectronic satellite spectra for highly charged He-like ions (1s2l"nl-1s2n'l', n, n'=2, 3) with Z=6-54

Relative intensities of dielectronic satellite lines determined by radiative transition probabilities and autoionization rates have been calculated for the transitions 1s2lnl-1s2nl, n, n=2, 3 in a wide range of nuclear charge Z. These data together with the wavelengths were computed for all satellite lines. Using these data synthetic spectra could be built for different plasma sources. Perturbation theory method has been applied for the calculation of atomic properties of autoionization states. Correlation, relativistic and radiative effects have been taken into account. Factor intensities Qd of dielectronic satellite lines are shown as functions of Z for different types of transitions. The Z-dependencies of the Qd values have been analysed and very pronounced sharp peaks have been discovered for this atomic characteristic indicating that some lines are prominent for specific ionic states and disappear for other ones. A possible explanation for such a behaviour of this atomic characteristic is presented. The resulting theoretical wavelengths for both satellite lines (1s2lnl-1s2nl, n, n=2, 3) and resonance lines (1snp 1,3Pt-1s2, n=2, 3 and 1s2s 1,3S-1s2) are compared with available experimental data along isoelectronic sequences to identify irregularities in the experimental data and to predict wavelengths of ions whose values are unknown or uncertain.

Spatial and temporal correlation in dynamic, multi-electron quantum systems

Cross sections for ionization with excitation and for double excitation in helium are evaluated in a full second Born calculation. These full second Born calculations are compared to calculations in the independent electron approximation, where spatial correlation between the electrons is removed. Comparison is also made to calculations in the independent time approximation, where time correlation between the electrons is removed. The two-electron transitions considered here are caused by interactions with incident protons and electrons with velocities ranging between 2 and 10 au. Good agreement is found between our full calculations and experiment, except for the lowest velocities, where higher Born terms are expected to be significant. Spatial electron correlation, arising from internal electron-electron interactions, and time correlation, arising from time ordering of the external interactions, can both give rise to observable effects. Our method may be used for photon impact.

He+ (np) cross sections for 2, 3, 4 and 5 MeV C4+ ions colliding with He atoms

Abstract The cross sections of ionization plus excitation of He are measured by the C4+ + He prototype reaction with energies ranging from 2 to 5 MeV. Theoretically the independent electron approximation is used to calculate the HeII (np) ionization plus excitation cross sections. The results of the calculations are compared with our experimental data.

Development of x‐ray and extreme ultraviolet (EUV) optical devices for diagnostics and instrumentation for various surface applications

New methods of surface-sensitive instrumentation for the diagnostics of extreme ultraviolet (EUV), soft x-ray (SXR) and x-ray radiation have been developed. In particular, these methods of instrumentation are of great importance for studies of the interaction of electron, ion and photon beams with matter (atoms, molecules, ions, clusters, surfaces, micro and submicron structures). Such collision studies are based on both glass capillary converters (GCCs) and multilayer mirrors (MLMs), gratings and crystals. The optical GCC device provides guiding, focusing and polarization analysis of short-wavelength radiation with a large bandwidth, and the MLM, grating and crystal optical elements are used for dispersing, focusing and polarization-sensitive studies of radiation within a more narrow bandwidth. In particular, we report here on the development of optical diagnostic devices, such as very compact EUV and SXR spectrometers, for measurements of polarization and spectral characteristics of short-wavelength radiation. Our high-throughput and high resolution compact spectrometers for the SXR range are based on grazing incidence spectrometers, MLMs and a sliced multi-layer grating (SMG) novel type of dispersion element. Furthermore, we will utilize a Schwarzschild objective with a spatial resolution of ∼0.1-0.3 pm for imaging surfaces following ion-surface interaction.

High-resolution EUV satellite spectra of doubly excited He I (nln'l'), n=2 to 5

High-resolution EUV spectra of doubly excited (nlnl) resonances in He I with n and n>or=2 have been studied by 2 and 5 MeV C4+ impact on He. Radiation from narrow and supernarrow He I resonances have been observed for the first time.

Ionization–excitation of helium to He+(2p) magnetic sublevels following electron, proton, and molecular hydrogen (H2+ and H3+) impact

Experimental magnetic sublevel scattering-angle-integrated cross sections following ionization–excitation of He(1s2)1S to He+(2p)2Po in e− + He and Hm+ + He (m = 1–3) collision systems have been determined using a combination of total cross sections and polarization fraction measurements in the extreme ultraviolet range. The derived magnetic sublevel cross sections, σ0 and σ1, for ML = 0 +/- 1 have been studied over a wide range of velocities (2–8.5 au) for electron impact on helium. These results are compared with previous experimental proton cross sections (2–6 au) as well as new measured data for hydrogen molecular impact (1.4–4.0 au) for equi-velocity. In addition, our electron and proton measurements are compared with earlier theoretical predictions, our recent second-Born calculations fully including off-shell energy terms, and present predictions from a hybrid first-order and second-order distorted-wave plus R-matrix (close-coupling) model (DWB1 + RMPS and DWB2 + RMPS). Finally, we have extended our polarization measurements for H+ + He collisions and found excellent agreement between theory and experiment at nearly all impact energies. However, the present second-Born and DWB1 + RMPS results deviate slightly from the experimental electron data while the DWB2 + RMPS calculations tend toward the experimental data of Forand et al (1985 J. Phys. B: At. Mol. Phys. 18 1409).

Theoretical analysis of the Doubly Excited 3lnl' States of Sodiumlike Copper

Energy levels, radiative transition probabilities and autoionization rates for CuXIX including the 1s22s22p53lnl (n = 3 ÷ 8, l ≤ n – 1) and 1s22s2p63lnl (n = 3 ÷ 4, l ≤ n – 1) doubly excited states were calculated using the multi-configurational Hartree–Fock method (Cowan code). Contributions of relativistic effects were discussed in comparison with data obtained by the multi-configurational Dirac–Fock method (YODA code). Application of the theoretical data for interpretation of experimental spectra obtained by double-electron capture in slow ion-atom collisions is discussed.

NEW COMPREHENSIVE THEORETICAL ANALYSIS OF THE DOUBLY EXCITED 3LNL' STATES OF SODIUM-LIKE IRON

Abstract Energy levels, radiative transition probabilities and autoionization rates for Fe XVI including the 1s 2 2s 2 2p 5 3 l n l ′ (n=3–8, l ′≤(n−1) ) and 1s 2 2s2p 6 3 l n l ′ (n=3–4, l ′≤(n−1)) doubly excited states were calculated by using the multi-configurational Hartree–Fock (Cowan code) method. The contribution of relativistic effects is studied in comparison with the data obtained using the multi-configurational Dirac–Fock (YODA code) method. The comparison of the theoretical data with experimental spectra obtained by double-electron capture in slow ion-atom collisions is discussed.