Abstract: Publisher Summary Density functional theory for stationary states or ensembles is a formulation of many-body theory in terms of the particle density Time-dependent density functional theory as a complete formalism is of more recent origin, although a time-dependent version This chapter describes the linear-response limit of time-dependent density functional theory along with applications to the photo-response of atoms, molecules and metallic surfaces Beyond the regime of linear response, the description of atomic and nuclear collision processes appears to be a promising field of application where the time-dependent Kohn and Sham (KS) scheme could serve as an economical alternative to time-dependent configuration-interaction calculation So far, only a simplified version of the time-dependent KS scheme has been implemented in this context Another possible application beyond the regime of linear response is the calculation of atomic multiphoton ionization which, in the case of hydrogen, has recently been found 54i55 to exhibit chaotic behavior A full-scale numerical solution of the time-dependent Schriidinger equation for a hydrogen atom placed in strong time-dependent electric fields has recently been reported A time-dependent Hartree–Fock calculation has been achieved for the multiphoton ionization of helium For heavier atoms an analogous solution of the time dependent Kohn-Sham equations offers itself as a promising application of time-dependent density functional theory

Abstract: Tenuous man-made plasmas in the Earth's atmosphere from sea level to 100 km are discussed. An ionization source generates a tenuous plasma with an electron number density n/sub e/ that is high near the source and diminishes with distance from the source. After the source shuts off, n/sub e/ decreases as a function of time as electrons recombine with positive ions or attach to negative ions. The electromagnetic properties that are essential to an understanding of these plasmas, which can be modeled as cold collisional plasmas, is discussed. Gas and plasma characteristics, such as momentum-transfer collision rate, plasma lifetime, recombination kinetics, and the effect of noble gases, are presented. Typical collision rates and plasma lifetimes at atmospheric pressure are quantified. Applications for a plasma with a gradient are discussed. They include a high-altitude plasma that can reflect or absorb from HF to VHF and a broadband atmospheric pressure absorber. The generation and use of plasma, including electron impact ionization with a high-energy electron-beam source and UV photoionization of an alkali vapor or an organic vapor such as tetrakis (dimethylamino)ethylene (TMAE), is described. The power required to sustain a plasma is quantified, and properties such as maximum absorption and bandwidth are discussed. Tradeoffs among maximum absorption, absorption bandwidth, duty ratio, and applied power permit optimization of absorption primarily at VHF. >

Abstract: A theoretical model of fatigue in ferroelectric thin‐film memories based upon impact ionization (e.g., Ti+4 to Ti+3 conversion in PbZr1−xTixO3), resulting in dendritic growth of oxygen‐deficient filaments, is presented. The predictions of spontaneous polarization versus switching cycles Ps(N) are compared with both Monte Carlo simulations for a two‐dimensional Ising model and with experimental data on small‐grain (40 nm) sol‐gel PZT films. Excellent agreement between theory and experiment is obtained. In addition to modeling the Ps(N) curves, the theory developed explains the observed linear proportionality between switching time ts(N) and polarization Ps(N) during fatigue; other models of aging do not account for this. Earlier theories of switching are also extended to include finite grain sizes, surface nucleation, triangular drive pulses, and dipolar forces. Good agreement with sol‐gel PZT switching data is obtained.

Abstract: Data are compiled and evaluated for collision processes of excitation, dissociation, ionization, attachment, and recombination of hydrogen molecules and molecular ions (H+2, H+3) by electron impact as well as for properties of their collision products.

Abstract: Absolute electron-impact cross sections have been measured from 0 to 200 eV for single ionization of 16 atoms (Mg, Fe, Cu, Ag, Al, Si, Ge, Sn, Pb, P, As, Sb, Bi, S, Se, and Te) with an estimated accuracy of \ifmmode\pm\else\textpm\fi{}10%. Combined with our recent measurements of He, Ne, Ar, Kr, Xe, F, Cl, Br, I, Ga, and In [Wetzel et al., Phys. Rev. A 35, 559 (1987); Hayes et al., ibid. 35, 578 (1987); Shul, Wetzel, and Freund, ibid. 39, 5588 (1989)], a set of 27 atomic single-ionization cross sections has now been measured with the same apparatus. In addition, cross sections are reported for double ionization of ten atoms and triple ionization of eight atoms. The measurements are made by crossing an electron beam with a 3-keV beam of neutral atoms, prepared by charge-transfer neutralization of a mass-selected ion beam. The critical measurement of absolute neutral beam flux is made with a calibrated pyroelectric crystal. The magnitudes of the single-ionization-peak cross sections decrease monotonically across rows of the periodic table from group IIIA (Al,Ga,In) to group VIIIA (Ar,Kr,Xe), varying much more than predicted by various empirical formulas and classical and quantum-mechanical theories.

Abstract: Recent literature relevant to the role of ion mobility spectrometry (IMS) in analytical chemistry is discussed. Included are sections dealing with instrumentation, spectral collection techniques, the theory of ion mobility in gases, and the dynamics of atmospheric pressure ionization. The pros and cons of radioactive ionization, photoionization, laser ionization, surface ionization, and electrofied spray ionization are considered. Analytical applications are separated into the use of IMS as a stand-alone spectrometer, and the use of IMS as a detector following gas, liquid, and supercritical fluid chromatography.

Abstract: PURPOSE:To obtain the electrophotographic sensitive body which has a high sensitivity and good repetitive stability by forming a charge transfer layer of two layers which respectively contain different charge transfer materials and specifying the ionization potentials of the respective layers to satisfy a specific relation. CONSTITUTION:This photosensitive body is constituted by successively laminating a charge generating layer 2, the charge transfer layer 3 and the charge transfer layer 4 on a conductive base body 1 and specifying the ionization potentials of the respective layers so as to satisfy the relation expressed by formula I. In the formula, Ig(G) denotes the ionization potential of the charge generating layer 2; Ip(T1) denotes the ionization potential of the charge transfer layer 3 in contact with the charge generating layer 2; Ip(T2) denotes the ionization potential of the charge transfer layer 4 in contact with the charge transfer layer 3. The higher sensitivity and better repetitive stability than the sensitivity and repetitive stability of the separated function type electrophotographic sensitive body formed by using one layer of the charge transfer layer are obtd. by laminating two layers of these charge transfer layers in such a manner.

Abstract: After defining the multiplication factor and the ionization rate together with their interrelationship, multiplication and breakdown models for diodes and MOS transistors are discussed. Different ionization models are compared and test structures are discussed for measuring the multiplication factor accurately enough for reliable extraction of the ionization rates. Multiplication measurements at different temperatures are performed on a bipolar NPN transistor, and yield new electron ionization rates at relatively low electrical fields. An explanation for the spread of the experimental values of the existing data on ionization rate is given. A new implementation method for a local avalanche model into a device simulator is presented. The results are less sensitive to the chosen grid size than the ones obtained from the existing method.

Abstract: In cases in which the ponderomotive energy is much larger than the ionization energy, which correspond to the highintensity limit or to the low-frequency limit, harmonic generation in gases near the ionization threshold can be understood from a plasma-physics point of view. Multiphoton ionization, which can be described by using the dc tunneling limit, takes place in a time interval localized around the maximum of the electric field. The plasma current thus generated varies on the same fast time scale and is responsible for harmonic generation. A model using those properties that has been developed shows the presence of a large number of odd harmonics.

Abstract: A particle-in-cell simulation is used to model the plasma generated in a parallel plate RF reactor at low pressure. Nonperiodic boundary conditions are used, and the electric field and particle motion are obtained by finite-difference methods leading to the self-consistent creation of sheaths on the boundaries. Model cross sections are used to describe collisions between particles. Ionization is included, and the plasma is maintained by fast electrons generated in the RF sheaths. Most of the power dissipation is due to the acceleration of ions in the time-average sheath fields. At high applied voltage, the power dissipation is described well by the power law P varies as V/sup 5/2/. Simple scaling laws for the density and plasma potential are obtained. The effect of ion mass and charge-exchange colisions on the ion energy spectrum collected by the electrodes is examined. The ion loss rate drops in the presence of charge-exchange collisions, and this leads to an increase in the density. The collisions also markedly alter the ion energy distribution function. >

Abstract: Ab initio calculations have been carried out on the first- and second-row transition-metal mono- and dicarbonyl positive ions. The bonding in these systems is discussed in detail. Trends in the series of mono- and dicarbonyl ions and between the first- and second-row transition metals are explained in terms of a dominantly electrostatic bonding interaction and differences in metal ion state separations, ionization potentials, and s and d orbital sizes. Dissociation energies are presented and a detailed comparison is made with experimental data. Where reliable experimental data exists, agreement with the theoretical results is generally good.

Abstract: Ionic transition-metal complexes have been difficult to analyze by mass spectrometry because of their low volatility, high thermal lability, and their tendency to undergo reduction during the ionization process. The authors have succeeded in generating, by electrospray ionization, intense beams of intact gas-phase cations from ionic transition-metal complexes, such as (Ru{sup II}(bpy){sub 3})Cl{sub 2} (where bpy = 2,2{prime}-bipyridyl) (I) and (Ru{sup II}(phen){sub 3})Cl{sub 2} (where phen = 1,10-phenanthroline) (II). In contrast to infrared laser desorption multiphoton ionization, fast atom bombardment, and field desorption, the cations observed from these complexes with electrospray ionization do not undergo reduction by electron or hydrogen transfer.

Abstract: High resolution laser excitation was combined with the technique of mass‐selected two‐photon ionization via a resonant intermediate state to measure rotationally resolved UV spectra of benzene–Ar van der Waals clusters. When the second laser pulse in the two color experiment is delayed by 7 ns no line broadening due to the second ionizing absorption step is observed. Spectra of three vibronic bands in the S1 ←S0 transition of benzene (h6)–Ar and benzene (d6)–Ar were measured yielding a line spectrum with a linewidth of 130 MHz. Resolution is sufficient to demonstrate that no asymmetry splitting of the rotational lines occurs and the spectrum is to a high precision that of a symmetric rotor. A detailed analysis of the rotational structure yields an accurate set of rotational constants. We find that the Ar is located on the C6 rotational axis. Its distance from the benzene ring plane is 3.582 A in the electronic ground state and decreases by 59±3 mA in the electronically excited state due to the increased polarizability of the benzene molecule after electronic excitation.

Abstract: Electron emission from clean gold under impact of ${\mathrm{H}}^{+}$ or singly charged rare-gas ions in their ground state has been investigated at the kinetic emission threshold, measuring both the emission statistics and total yields by means of counting techniques. As we are able to subtract any contribution from potential emission, we observe kinetic emission well below the threshold for sufficient energy transfer from projectiles onto quasifree metal electrons and relate this contribution to quasimolecular autoionization in close collisions between the neutralized projectiles and metal ion cores.

Abstract: The possibility of using a high-intensity optical field in conjunction with a gas target to produce a highly ionized plasma filament suitable for recombination XUV lasers in both transient and quasi-steady-state regimes is examined. A distinction is made between low Z ions which can be stripped to the desired ionization state at nonrelativistic intensities and higher Z ions which require relativistic intensities to produce the desired ionization. In the nonrelativistic case (E/sub i/ >

Abstract: The threshold photoionization efficiency (PIE) curves for nickel clusters in the size range Ni3 to Ni90 have been measured by laser photoionization with detection by time‐of‐flight mass spectrometry. Both warm (≤298 K) and cold (≤77 K) clusters have been studied. The PIE curves for 298 K clusters display thermal tails, while these tails are smaller for cold clusters. Cluster ionization potentials (I.P.s) have been determined by two methods: the Watanabe procedure and linear extrapolation of the PIE curves. Dramatic dependence of I.P. on cluster size is found for clusters smaller than 11 atoms, while the I.P.s of larger clusters decrease relatively smoothly and nearly monotonically from 5.84 eV for Ni11 to 5.56 eV for Ni90. The I.P.s for clusters larger than Ni40 show the linear dependence on reciprocal radius (R−1) predicted by the conducting spherical drop model of small particle I.P.s, but do not fit the model quantitatively unless the limiting (R−1→ 0) work function is reduced by 0.46 eV from the bulk ...

Abstract: Particle‐in‐cell simulations of radio frequency glow discharges between parallel‐plate electrodes were performed to test the role of secondary emission at applied frequencies above the ion plasma frequency. With the secondary electron emission coefficient set to zero, the high‐energy tail of the electron energy distribution function in the center of the glow is modulated at the applied frequency, and these energetic electrons show substantial anisotropy. In addition, a pulse of ionization propagates across the glow, correpsonding to the directed velocity of the high‐energy electrons in the center of the glow. These high‐energy electrons originate at the plasma‐sheath boundary and appear to be the result of sheath heating.

Abstract: Diatomic nickel–copper, NiCu, has been investigated by resonant two‐photon ionization spectroscopy in a jet‐cooled molecular beam Six band systems have been identified over the range 11 500–16 500 cm−1 The ground state of NiCu has been determined to be X 2Δ5/2, with ω‘e =27301±115 cm−1, ω″ex‘e =100±038 cm−1, and r″e =2233±0006 A This state derives from a strongly bound (205±010 eV) 3d10Cu3d9Ni 4sσ2 configuration Excited states observed in this work derive from the more weakly bound 3d10Cu3d8Ni 4sσ24sσ*1 configuration, and are characterized by smaller vibrational frequencies (191–208 cm−1) and a longer bond length (2351±0005 A) than the ground X 2Δ5/2 state

Abstract: A procedure is described for the determination of metal cluster ionization potentials (IPs) using available excimer laser lines that gives error limits substantially smaller than traditional bracketing experiments. It is based on the observation that the adsorption of ammonia on cluster surfaces lowers cluster IPs, and that the IP lowering is linear in the number of adsorbed NH3 molecules. By determining the minimum number of NH3 molecules needed for ionization by the various excimer lasers, an approximation to the dependence of IP on coverage can be deduced. Extrapolation of this dependence to zero coverage gives the bare cluster IPs. Results are presented for clusters of iron, cobalt, and nickel having from 4 to 100 atoms. The effect of molecular adsorption on cluster IPs is analyzed theoretically, and the comparison with experimental results used to estimate the effective dipole moment of NH3 molecules adsorbed on these clusters. Comparison of the bare cluster IPs with the simple spherical drop model s...

Abstract: The photoionization efficiency (PIE) spectra for niobium clusters up to Nb76 are measured using laser ionization time‐of‐flight mass spectrometry Ionization potentials (IPs) assigned from the PIE spectra evolve with the same general pattern observed for other transition metal clusters (Mn) studied to date: a rapid yet nonmonotonic decrease in IP to n≂15 followed thereafter by a relatively slow and smooth evolution The measured IPs evolve with cluster radius R according to the predictions of the conducting spherical droplet model if the limiting (R→∞) IP is chosen to be 05 eV lower than the bulk polycrystalline work function Kinetics experiments using D2 as the coreactant indicate the existence of two structural forms, one highly reactive, one relatively unreactive for clusters in the size range Nb9–Nb12, with the reactive forms predominant in each case PIE spectra for Nb9–Nb12 were recorded using sufficient D2 added to the cluster source to selectively titrate the reactive forms of these clusters, le

Abstract: An electron-irradiation induced crystalline-to-amorphous (C-A) transition in α-Sic single crystals of the 6H polytype has been studied as a function of irradiation temperature, incident electron energy and orientation of the incident beam, by means of ultra-high voltage electron microscopy. The C-A transition can be induced at temperatures below 290 K. The minimum energy of incident electrons to cause the C-A transition is 725 ± 25 keV. The electron dosage required for the C-A transition is essentially constant at temperatures below 220 K, while at temperatures above 220 K, the dosage increases quickly with temperature until no amorphization can be induced any more at the critical temperature of 290 K. At fixed temperatures below the critical temperature, the required dosage decreases with increasing incident electron energy. The temperature and incident energy dependence of the required dosage indicate that a knock-on mechanism rather than an ionization mechanism is responsible for the C-A trans...

Abstract: Photoionization of phenol(B) n (B=NH 3 , C 2 H 5 NH 2 ) clusters formed in a supersonic expansion has been studied by the mass-selected two-color two-photon resonance-enhanced multiphoton ionization technique. This study clearly shows that a reaction of proton transfer takes place in the excited state (S 1 ) of the neutral clusters, depending on the nature of the base molecule (B) and the size of the cluster. The clusters with n≤3 for ammonia and n≤2 for monoethylamine show an ionization cross section steeply increasing in the 7.5-7.8-eV range. This corresponds to the vertical ionization potential of the clusters lowered by about 1 eV with respect to free phenol, due to hydrogen bonding

Abstract: Unimolecular dissociation channels of mass-selected doubly charged sodium clusters ${\mathrm{Na}}_{\mathit{n}}^{++}$ have been determined for cluster sizes near and above the critical size, ${\mathit{n}}_{\mathit{c}}$=27, from which doubly charged clusters are detectable in mass spectra. On a time scale of 50 \ensuremath{\mu}s with respect to ionization, doubly charged clusters of size n=${\mathit{n}}_{\mathit{c}}$ are found to fission asymmetrically. For cluster sizes above ${\mathit{n}}_{\mathit{c}}$, however, evaporation of a neutral monomer is the dominant channel for delayed dissociation. An estimation of the height of the Coulombic barrier is given for ${\mathrm{Na}}_{\mathit{n}}^{++}$ near the critical size, using the framework of statistical theory.

Abstract: Improved techniques are provided for forming ionized molecules from electrosprayed droplets for analysis by a mass spectrometer. A high voltage is applied to a capillary tube for spraying droplets at substantially atmospheric pressure or above, and the electrosprayed droplets contain sample solute of interest and solvent. The electrosprayed droplets are passed into an ion generating chamber which is maintained at a pressure in the range of from 0.1 Torr to 10 Torr. The walls of the ion generating chamber are controllably heated to a temperature which will desolvate the droplets and produce ionized molecules of interest for analysis by the mass spectrometer. The electrospray technique does not rely upon a countercurrent heated gas flow, and provides a particularly simple and inexpensive means to couple electrospray ionization to either quadrupole or magnetic mass analyzers.

Abstract: A single-center coupled-channel code based on an expansion in terms of atomic wave functions that includes dynamic curved projectile trajectories is applied to the calculation of stopping powers. Stopping powers and differential ionization cross sections are evaluated for p\ifmmode\bar\else\textasciimacron\fi{}, ${\mathrm{H}}^{+}$, ${\mathrm{He}}^{2+}$, and ${\mathrm{Li}}^{3+}$ projectiles penetrating atomic H and He targets at energies of 10--500 keV/u. The results are compared to experimental data, to predictions of the first-order plane-wave Born approximation, and to results of calculation for excitation of a harmonic oscillator including Barkas corrections. The improvement of the present model to first-order or second-order perturbative treatments as well as the effect of polarization on the projectile trajectories is discussed.