Theoretical and experimental studies of the valence photoemission spectrum of propionitrile
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A method is described for measuring photo-ionization efficiency (PE) curves over the energy range 9–14 eV. The method is experimentally easier than measuring the photo-ionization cross section and gives essentially the same result. PE curves are given for Xe, O2, and NO and first ionization potentials are determined; Xe, 12.129±0.002 eV; O2, 12.065±0.003 eV; and NO, 9.250±0.005 eV. It has been established that steps in the PE curve of NO give a quantitative measure of the energies of the vibrational levels in the NO+ ion and that peaks in the curves of all three gases correspond to neutral levels that auto-ionize. The probability laws for ionization and auto-ionization are discussed.
Thermal ionization
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The change of ionization cross section in the thermodynamic theory of impact ionization that describes a complete ionization curve was determined for a concentration of helium atoms of 1.9 X 10/sup -13/ cm/sup -3/ means of theoretical and experimental methods. The change of ionization cross section was studied by utilizing the thermodynamic theory of impact ionization. Results indicate that the concentration dependence of the rest of the curve is evidence that at each energy value the ionization cross section has the property of a constant. This indicates that at some increase of ionization potential the effect of concentration on the ionization curve disappears, and at each energy value the cross section takes on the properties of a constant.
Thermal ionization
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Electron-impact direct double ionization (DDI) process is studied as a sequence of two and three step processes. Contribution from ionization-ionization, ionization-excitation-ionization, and excitation-ionization-ionization processes is taken into account. The present results help to resolve the long-standing discrepancies; in particular, a good agreement with experimental measurements is obtained for double ionization cross-sections of $O^{1+}$, $O^{2+}$, $O^{3+}$, $C^{1+}$, and $Ar^{2+}$ ions. We show that distribution of the energy of scattered and ejected electrons, which participate in the next step of ionization, strongly affects DDI cross-sections.
Double ionization
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Atmospheric-pressure laser ionization
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Energy levels, with designations and uncertainties, have been compiled for the spectra of barium (Z=56) ions from doubly ionized to hydrogenlike. Wavelengths with classifications, intensities, and transition probabilities are also tabulated. In addition, ground states and ionization energies are listed. For many ionization stages experimental data are available; however, for those for which only theoretical calculations or fitted values exist, these are reported. There are a few ionization stages for which only a calculated ionization potential is available.
Barium
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The ionization potential of O 2 has been measured by the technique of high resolution photo-electron spectroscopy taking into account the influence of rotational structure on the shape of the vibrational bands. A value of 12.071 ± 0.001 eV (1027.1 ± 0.1 Å) was found for the ionization potential. This value leads to a dissociation energy of D 0 (O 2 + X 2 Π g ) = 6.661 ± 0.001 eV. A lowering of the ionization potential caused by a branch head when ΔN = −2 gave an appearance potential for ionization of 12.068 ± 0.001 eV (1027.4 ± 0.1 Å).
Bond-dissociation energy
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The surface ionization method offers the possibility of measuring ionization energies of atoms, inorganic and organic molecules and clusters. In this study we report the results of the surface ionization of Li2F molecules on a rhenium surface. This work is an attempt to investigate the applicability of the surface ionization technique for the measurment of the ionization energies of hypervalent molelcules at high temperature. There are currently no reliable experimental data for the ionization energy of the Li2F molecule. This molecule has been chosen because previous theoretical calculations have shown that Li2F is a hypervalent (hyperlithiated) molecule with a low ionization energy. The ionization energy was determined to be 5.42±0.04 eV.
Hypervalent molecule
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Atoms in molecules
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Thermal ionization
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A detailed investigation of multiple ionization of He (ionization charge states q=1,2), Ne (q=1--3), and Ar and Kr (q=1--4) is presented for proton impact energies ranging from 10 keV to a few MeV. Absolute cross sections for various ionization pathways have been obtained by combining some new measurements with previously published experimental results and, in certain cases, with existing theoretical information. It is shown how each of these pathways contribute to the various stages of target ionization that are observed after the collision and how these experimentally measured quantities are related to the cross sections for initial inner- and outer-shell vacancy production. Areas where additional data are required or where the existing data are not internally consistent are pointed out. In general, it is shown that the existing data are sufficient to describe the ionization of helium as well as the lower levels of ionization of neon, argon, and krypton. However, for the higher degrees of ionization, particularly for Kr, our understanding is hampered by substantial gaps in the available inner-shell ionization data---both in cross-section and branching-ratio information. Nevertheless, the data are sufficient to indicate the relative importance of the various pathways. For all targets, direct multiple outer-shell cross sections were extracted. Analyzing the energy dependences of these cross sections provided some hints as to how to calculate multiple-ionization cross sections, e.g., information as to where the multiple ionization is dominated by the first-order or by a higher-order term in the perturbation expansion of the proton-target interaction is obtained.
Krypton
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The ionization efficiency curves for the 3-fold ionization of Ar, and the 3, 4, 5, and 6-fold ionization of Xe have been examined. It is shown that, near the threshold, the probability of n-fold ionization varies as the nth power of the excess electron energy for n = 3 and 4, and probably also for n = 5 and 6. The determination of appearance potentials for such processes is discussed.
Thermal ionization
Atmospheric-pressure laser ionization
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