Absolute dipole oscillator strengths for photoabsorption and photoionization of carbon disulphide

The absolute dipole oscillator strengths (cross-sections) for photoabsorption and photoionization (total and partial) of CS₂ have been obtained in the 5–40 eV energy range by magic-angle dipole (e, 2e) spectroscopy. Very strong absorption is detected below 20 eV, much of which is attributable to the excitation of molecules decaying by autoionization processes. Analysis of binding energy spectra taken at energy losses above 20 eV reveals extensive satellite structure in the range up to 35 eV. This structure is attributed to many-electron effects consistent with theoretical calculations found in the literature. Photoelectron branching ratios for CS₂ are also reported.     

Electron spectroscopy using excited atoms and photons; VIII penning ionization of the hydrogen halides

Electron spectra resulting from collisions of thermal 2³S metastable helium atoms with HF, HCl, HBr and HI are compared with the respective 584     

Experimental and theoretical binding energy spectra and momentum distributions for the valence orbitals of H2O

The binding energy spectra (10–46 eV) and momentum distributions of the valence orbitals of H₂O have been measured using a new high-sensitivity binary (e,2e) electron spectrometer employing position-sensitive detectors. The binding energy spectrum shows a previously unreported feature at = 27 eV which is shown to be associated with the (2a₁)^?1 ionization process. The region between 25 and 46 eV is compared with previous (e,2e) and X-ray photoelectron measurements as well as with several existing and new many-body calculations indicating a splitting of the 2a₁ ionization pole strength. In addition the separate momentum distributions of the three outer valence orbitals of H₂O have been obtained from deconvoluted binding energy spectra run at a series of azimuthal angles. The results, which show considerably improved signal-to-noise ratio over earlier measurements using single-channel instrumentation are compared with spherically averaged momentum distributions calculated with a variety of wavefunctions.     

X-ray photoelectron study of some silicon-oxygen compounds

More than fifty specimens of silicon-oxygen compounds have been studied by X-ray photoelectron spectroscopy. Due to the insulating properties of these specimens the measured binding energies of the various atomic levels were corrected using the C (1s) line due to hydrocarbon contamination as a reference. A statistical treatment of the experimental results has been used to verify the validity of the reference and to discuss the differences in binding energy of the Si (2p) line in various samples. Three different steps of oxidation have been found for silicon; the chemical shifts with respect to unoxidised silicon are 3.2, 4.1 and 5.0 eV for surface oxidised silicon, silicates and quartz, respectively. The influence of atoms other than oxygen in the neighbourhood of silicon, such as fluorine or alkaline cations is discussed.     

Valence-shell momentum distributions and ionization energies of carbon disulfide

Valence-shell binding energy spectra and momentum distributions of CS₂ have been measured using non-coplanar symmetric binary (e,2e) spectroscopy. The present measurements are compared with previously published binding energy spectra calculated using the many body 2ph-TDA Green's function (GF) method and the symmetry-adapted cluster configuration-interaction (SAC CI) method. The measured and the calculated binding energy spectra both show extensive population splittings particularly above 20 eV, confirming a significant breakdown of independent particle ionization picture. A relatively strong-outer valence many-body state at 17.0 eV is shown to be satellite of the (2π₀)^?1 state, in accord with earlier conclusions of photoelectron studies. Momentum distributions measured at several carefully chosen binding energies are compared with the corresponding molecular orbital momentum distributions calculated using small and extended gaussian basis sets. The good qualitative agreement between momentum distributions measured in the inner-valence region wth theoretical 4σ_m and 5σ_g orbital momentum distributions confirms the qualitative predictions of satellite parentages by GF and SAC CI calculations. Momentum and position density contour maps of individual orbitals are used to interpret the shapes and atomic characters of the experimental momentum distributions. Momentum densities of the valence orbitals of CS₂ are compared with those of the respective valence isoelectronic species CO₂     

Electron coincidence spectroscopy of O2: Valence electron momentum distributions and binding energies

The binding energy spectra and momentum distributions for the valence orbital transitions of molecular oxygen have been obtained using the (e,2e) reaction at total electron energies of 400 and 1200 eV. The outer π_g orbital is found to have a wave-function which is significantly more extended in momentum space than that of the more-tightly bound π_u orbitals. This is interpreted as a consequence of the single occupancy of the anti-bonding π_g orbitals. Peaks at 39 and 47 eV are assigned to ^4,2Σ_g⁻ ion states on the basis of the observed momentum distributions. The momentum distribution and observed intensity for the 32.5 eV transition supports the assignment of 2 Π_u for this ion state. The measured relative strengths for the various Π_u and Σ_u transitions are in qualitative agreement with CI and Green's function calculations.     

The absolute partial photoionization cross section for the production of the X 2B1 state of H2O+

The absolute partial photoionization cross section for the production of the ground state of the water molecule ion has been measured from threshold up to an equivalent photon energy of 34 eV using dipole (e,2e) spectroscopy. This data obtained from a constant ionic state scan is consistent with earlier dipole (e,2e) measurements obtained from photoelectron branching ratios and the total photoabsorption measurement. The new data which extends to lower energy is compared with two recent independent measurements obtained using tuneable synchrotron radiation. These two synchrotron radiation measurements are in disagreement with each other in the region between 18 and 22 eV where the two data sets overlap. While good agreement is obtained with the work of Truesdale et al. above 22 eV significant differences exist at lower energies. In contrast good agreement is found with the work of Dutuit et al. from threshold up to 17.5 eV and at 20 eV but not in the intervening region. The measurements are also compared with the results of a variety of earlier reported theoretical calculations.     

Synthesis of substituted quinolines by iron-catalyzed coupling reactions between chloroenynes and Grignard reagents

This letter reports the preparation of quinolines, substituted at the 2- or 3-position by a 4-substituted but-3-en-1-yne group, by the environmentally friendly iron(III)-catalyzed coupling reaction of Grignard reagents with 1-chloro-4-(2-quinolyl)but-1-en-3-yne. The extension and the scope of this non-toxic and chemoselective procedure to various functionalized unsaturated vinyl chlorides are described.     

Binding energies at different momenta for the valence orbitals of HCl by the binary (e, 2e) method

The binding energy spectra for the valence orbitals of hydrogen chloride have been obtained using the binary (e,2e) method at 1200 eV. The strength of the innermost valence orbital (4σ) is severely split among several ion states in the energy range 25 to 41 eV. The measured cross sections are compared with results of calculations using contracted Gaussian basis sets of double-zeta quality, and with a one-particle Green's function calculation.