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Koichi Ohno - One of the best experts on this subject based on the ideXlab platform.
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two dimensional Penning Ionization electron spectroscopy of open shell metallocenes outer valence ionic states of vanadocene and nickelocene
Journal of Physical Chemistry A, 2013Co-Authors: Naoki Kishimoto, Miku Kimura, Koichi OhnoAbstract:In order to investigate outer valence ionic states of open-shell metallocenes, we have applied two-dimensional collision-energy/electron-energy-resolved Penning Ionization electron spectroscopy (2D-PIES) upon collision with metastable He*(2(3)S) excited atoms as well as a high level ab initio molecular orbital calculation (the partial third-order quasiparticle theory of the electron propagator (P3)) to Ionization from neutral ground states of vanadocene ((4)A2g) and nickelocene ((3)A2g). Assignments of observed Penning Ionization electron/He I ultraviolet photoelectron spectra were consistent with the P3 calculation results for Ionization of α and β spin electrons except for electron correlation bands observed by PIES. Negative collision energy dependence of partial Penning Ionization cross-sections (CEDPICS) indicate attractive interaction with He*(2(3)S) around the molecule. Results by model potential calculation utilizing Li(2(2)S) instead of He*(2(3)S) for interaction between He*(2(3)S) and open-shell metallocenes do not explain the strong negative CEDPICS of the bands observed in PIES.
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Collision-Energy-Resolved Penning Ionization Electron Spectroscopy of Glycine with He(23S) Metastable Atoms: Conformational Isomers in Collisional Ionization
The journal of physical chemistry. A, 2009Co-Authors: Yoshihiro Yamakita, Koichi OhnoAbstract:Conformationally dependent Ionization of the simplest amino acid, glycine, is studied by Penning Ionization electron spectroscopy with velocity-resolved metastable He*(23S) atoms. The observed He I ultraviolet photoelectron and Penning Ionization electron spectra are reproduced by superimposed theoretical spectra, assuming thermal distributions of conformers. The conformations of amino acids are determined by analyzing the observed Penning Ionization cross sections, peak shifts, and collision energy dependences of partial Ionization cross sections (CEDPICS). The Penning Ionization cross sections are governed by collisionally accessible exterior electron densities. When the amino and carbonyl groups are exposed to He* access, the nonbonding orbitals of N (nN) and O atoms (nO) give rise to strong bands. The observed negative peak shifts and negative CEDPICS for the nN and nO orbitals suggest the presence of attractive interactions around their electron distributions. The most attractive wells are estimated ...
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stereodynamics and outer valence ionic states of ferrocene in collisional Ionization with a he 23s metastable atom by two dimensional Penning Ionization electron spectroscopy
Journal of Physical Chemistry A, 2009Co-Authors: Naoki Kishimoto, Koichi OhnoAbstract:Outer valence ionic states of ferrocene were investigated by means of Penning Ionization electron spectroscopy upon collision with metastable He*(2(3)S) excited atoms. By two-dimensional measurement combining electron spectroscopy and collision-energy-resolved technique of the metastable atomic beam, ionic-state-resolved measurements of collision energy dependence of partial Penning Ionization cross sections (CEDPICS) were carried out. Since the partial Penning Ionization cross sections can be connected with spatial extension of corresponding molecular orbitals (MOs) outside the boundary surface for the collision with He* atoms, different slope values of CEDPICS were related with stereodynamics in Penning Ionization as well as anisotropic interaction around the Ionization region: attractive interaction around ligand pi orbitals and repulsive interaction around ligand sigma orbtials and the metal atom. The observed negative collision energy dependence of Ionization cross sections for the first ((2)E(2)') and second ((2)A(1)') ionic states was consistent with configuration interactions suggested by ab initio MO calculations [J. Chem. Phys. 2002, 117, 6533], which is due to the strong electron correlation effects beyond the one-electron MO description.
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Two-dimensional Penning Ionization electron spectroscopic study on outer characteristics of molecules
Journal of Electron Spectroscopy and Related Phenomena, 2005Co-Authors: Koichi Ohno, Masakazu Yamazaki, Satoshi Maeda, Naoki KishimotoAbstract:Abstract Collision-energy/electron-energy-resolved two-dimensional Penning Ionization electron spectroscopy (2D-PIES) has been used to study outer characteristics of molecules. Anisotropic potential energy surfaces for collisional Ionization of molecules with a metastable helium atom He*(2 3 S) have been determined starting from ab initio model potentials via optimization based on trajectory calculations. Since Ionization widths in the theoretical model of Penning Ionization are functionals of target molecular orbitals, outer electron distributions of molecular orbitals can be determined via optimization procedures of calculated Ionization cross-sections by trajectory calculations with respect to observed 2D-PIES data.
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Collision-energy-resolved Penning Ionization electron spectroscopy of substituted ethylenes
Journal of Electron Spectroscopy and Related Phenomena, 2004Co-Authors: Naoki Kishimoto, Takeo Oda, Koichi OhnoAbstract:Abstract Collision-energy-resolved Penning Ionization electron spectra of NH 2 CH 2 CH 2 CN and HOCH 2 CH 2 CN by He ∗ (2 3 S) metastable atoms were observed. Ionization from orbitals extending around CN groups shows large intensity, negative collision energy dependence of partial Ionization cross sections (CEDPICS) and negative peak energy shift with respect to the estimated peak positions at Ionization energies, and attractive interactions around the nitrile group were obtained by model potential energy calculations. Attractive interactions around NH 2 and OH groups also result in negative CEDPICS and negative peak energy shift. Observed bands in photoelectron spectrum and Penning Ionization electron spectrum of NH 2 CH 2 CH 2 CN can be ascribed to Ionization from two conformers as calculated by a theoretical method.
Naoki Kishimoto - One of the best experts on this subject based on the ideXlab platform.
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two dimensional Penning Ionization electron spectroscopy of open shell metallocenes outer valence ionic states of vanadocene and nickelocene
Journal of Physical Chemistry A, 2013Co-Authors: Naoki Kishimoto, Miku Kimura, Koichi OhnoAbstract:In order to investigate outer valence ionic states of open-shell metallocenes, we have applied two-dimensional collision-energy/electron-energy-resolved Penning Ionization electron spectroscopy (2D-PIES) upon collision with metastable He*(2(3)S) excited atoms as well as a high level ab initio molecular orbital calculation (the partial third-order quasiparticle theory of the electron propagator (P3)) to Ionization from neutral ground states of vanadocene ((4)A2g) and nickelocene ((3)A2g). Assignments of observed Penning Ionization electron/He I ultraviolet photoelectron spectra were consistent with the P3 calculation results for Ionization of α and β spin electrons except for electron correlation bands observed by PIES. Negative collision energy dependence of partial Penning Ionization cross-sections (CEDPICS) indicate attractive interaction with He*(2(3)S) around the molecule. Results by model potential calculation utilizing Li(2(2)S) instead of He*(2(3)S) for interaction between He*(2(3)S) and open-shell metallocenes do not explain the strong negative CEDPICS of the bands observed in PIES.
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stereodynamics and outer valence ionic states of ferrocene in collisional Ionization with a he 23s metastable atom by two dimensional Penning Ionization electron spectroscopy
Journal of Physical Chemistry A, 2009Co-Authors: Naoki Kishimoto, Koichi OhnoAbstract:Outer valence ionic states of ferrocene were investigated by means of Penning Ionization electron spectroscopy upon collision with metastable He*(2(3)S) excited atoms. By two-dimensional measurement combining electron spectroscopy and collision-energy-resolved technique of the metastable atomic beam, ionic-state-resolved measurements of collision energy dependence of partial Penning Ionization cross sections (CEDPICS) were carried out. Since the partial Penning Ionization cross sections can be connected with spatial extension of corresponding molecular orbitals (MOs) outside the boundary surface for the collision with He* atoms, different slope values of CEDPICS were related with stereodynamics in Penning Ionization as well as anisotropic interaction around the Ionization region: attractive interaction around ligand pi orbitals and repulsive interaction around ligand sigma orbtials and the metal atom. The observed negative collision energy dependence of Ionization cross sections for the first ((2)E(2)') and second ((2)A(1)') ionic states was consistent with configuration interactions suggested by ab initio MO calculations [J. Chem. Phys. 2002, 117, 6533], which is due to the strong electron correlation effects beyond the one-electron MO description.
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Two-dimensional Penning Ionization electron spectroscopic study on outer characteristics of molecules
Journal of Electron Spectroscopy and Related Phenomena, 2005Co-Authors: Koichi Ohno, Masakazu Yamazaki, Satoshi Maeda, Naoki KishimotoAbstract:Abstract Collision-energy/electron-energy-resolved two-dimensional Penning Ionization electron spectroscopy (2D-PIES) has been used to study outer characteristics of molecules. Anisotropic potential energy surfaces for collisional Ionization of molecules with a metastable helium atom He*(2 3 S) have been determined starting from ab initio model potentials via optimization based on trajectory calculations. Since Ionization widths in the theoretical model of Penning Ionization are functionals of target molecular orbitals, outer electron distributions of molecular orbitals can be determined via optimization procedures of calculated Ionization cross-sections by trajectory calculations with respect to observed 2D-PIES data.
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Collision-energy-resolved Penning Ionization electron spectroscopy of substituted ethylenes
Journal of Electron Spectroscopy and Related Phenomena, 2004Co-Authors: Naoki Kishimoto, Takeo Oda, Koichi OhnoAbstract:Abstract Collision-energy-resolved Penning Ionization electron spectra of NH 2 CH 2 CH 2 CN and HOCH 2 CH 2 CN by He ∗ (2 3 S) metastable atoms were observed. Ionization from orbitals extending around CN groups shows large intensity, negative collision energy dependence of partial Ionization cross sections (CEDPICS) and negative peak energy shift with respect to the estimated peak positions at Ionization energies, and attractive interactions around the nitrile group were obtained by model potential energy calculations. Attractive interactions around NH 2 and OH groups also result in negative CEDPICS and negative peak energy shift. Observed bands in photoelectron spectrum and Penning Ionization electron spectrum of NH 2 CH 2 CH 2 CN can be ascribed to Ionization from two conformers as calculated by a theoretical method.
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Two-dimensional Penning Ionization electron spectroscopy of CH2ClI and CH2ClCN
The Journal of Physical Chemistry A, 2003Co-Authors: Shan Xi Tian, Naoki Kishimoto, Koichi OhnoAbstract:The electronic structures of CH2ClI and CH2ClCN and anisotropic interactions with the metastable He*(23S) atoms are studied by two-dimensional (electron-energy and collision-energy-resolved) Penning Ionization electron spectroscopy as well as He I ultraviolet photoelectron spectroscopy. A broad band with the high Ionization potentials in the Penning Ionization electron spectrum of CH2ClI is proposed to be related to autoIonizations of the Cl** or I** species produced through dissociations after the excitation transfer from the He* atom. The split bands having the characteristics of the Cl and I lone pair electrons (nCl and nI) are observed in the spectra, as being interpreted by the intramolecular orbital (nCl ↔ nI and nCl ↔ πCN) through-space/through-bond interactions rather than the spin−orbit coupling effects. The magnitude of intramolecular orbital nCl ↔ πCN interactions is much stronger than that of the nCl ↔ nI interactions. The collision energy dependence of partial Penning Ionization cross section...
Toshio Kasai - One of the best experts on this subject based on the ideXlab platform.
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Probing branching mechanism through resonance-type oscillation in the collision-energy dependence of Penning Ionization reaction of Ar (3P) with oriented CH3I
The Journal of Chemical Physics, 2003Co-Authors: Seiki Okada, Hiroshi Ohoyama, Toshio KasaiAbstract:The collision energy and orientation-angle-resolved Penning Ionization cross sections were determined for the Ar (3P)+CH3I reaction. A remarkable depletion was recognized in the collision- energy dependence of the orientation-angle-resolved Penning Ionization cross section. The depletion could be interpreted as the competitive neutral dissociation from the Rydberg states formed by an electron exchange mechanism related to a 3a1 molecular orbital. The stereo selectivity for the Penning Ionization and neutral dissociation were discussed. From the series of our studies on Ar (3P)+CH3X (X=Cl,Br,I) reactions, it was substantiated that the orientation angle and collision-energy-resolved Penning Ionization cross section give an important information about the branching mechanism to the Rydberg states that are linked to the neutral dissociation channels.
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Collision-energy resolved steric effect on the Penning Ionization reaction of tert-butyl bromide and Kr(3P)
Chemical Physics Letters, 2003Co-Authors: Kenichi Koizumi, Hiroshi Ohoyama, Toshio KasaiAbstract:Abstract Collision energy dependence of the Penning Ionization cross-section for the Kr( 3 P) + (CH 3 ) 3 CBr → Kr + (CH 3 ) 3 CBr + + e − reaction was determined under orientation-angle resolved condition using an oriented (CH 3 ) 3 CBr beam and time-of-flight measurements. A remarkable resonance-type structure was found in the energy dependence of orientation-angle resolved Penning Ionization cross-section. This resonance-type structure could be interpreted as a new-type ‘nuclear-excited Feshbach resonance’ in the formation of vibrational excited Rydberg states leading to a competitive dissociative exit channel.
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Direct observation of the steric effect in Penning Ionization reaction of Ar*+CHCl3→CHCl2++Cl+e−+Ar
The Journal of Chemical Physics, 2000Co-Authors: Masanori Yamato, Seiki Okada, Hiroshi Ohoyama, Toshio KasaiAbstract:Steric effect in the Penning Ionization reaction of Ar*(3P2,0)+CHCl3→Ar+CHCl2++Cl+e− was directly observed at an average collision energy of 0.13 eV using the oriented CHCl3 molecular beam. The product CHCl2+ ions are measured for the H-end, the CCl3-end, and sideways orientations. The obtained steric opacity function reveals that the CCl3-end orientation is more favorable than the H-end orientation, and the sideways approach is found to be more favorable than the collinear approaches from both ends of the molecule. Furthermore, we confirm the good correlation between Penning Ionization anisotropy and the electron density distribution of the 2a2 HOMO orbital of the CHCl3 molecule, whose electron cloud is mostly localized around the sideways. These results substantiate the electron exchange mechanism which is commonly accepted for the Penning Ionization reaction, where the overlap of projectile atomic and target molecular orbital plays a key role in Penning Ionization efficiency.
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direct observation of the steric effect in Penning Ionization reaction of ar chcl3 chcl2 cl e ar
Journal of Chemical Physics, 2000Co-Authors: Masanori Yamato, Seiki Okada, Hiroshi Ohoyama, Toshio KasaiAbstract:Steric effect in the Penning Ionization reaction of Ar*(3P2,0)+CHCl3→Ar+CHCl2++Cl+e− was directly observed at an average collision energy of 0.13 eV using the oriented CHCl3 molecular beam. The product CHCl2+ ions are measured for the H-end, the CCl3-end, and sideways orientations. The obtained steric opacity function reveals that the CCl3-end orientation is more favorable than the H-end orientation, and the sideways approach is found to be more favorable than the collinear approaches from both ends of the molecule. Furthermore, we confirm the good correlation between Penning Ionization anisotropy and the electron density distribution of the 2a2 HOMO orbital of the CHCl3 molecule, whose electron cloud is mostly localized around the sideways. These results substantiate the electron exchange mechanism which is commonly accepted for the Penning Ionization reaction, where the overlap of projectile atomic and target molecular orbital plays a key role in Penning Ionization efficiency.
Yoshihiro Yamakita - One of the best experts on this subject based on the ideXlab platform.
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Development of a highly-sensitive Penning Ionization electron spectrometer using the magnetic bottle effect
2016Co-Authors: Masahiro Ota, Yuki Ishiguro, Yutaro Nakajima, Naoya Miyauchi, Yoshihiro YamakitaAbstract:This paper reports on a highly-sensitive retarding-type electron spectrometer for a continuous source of electrons, in which the electron collection efficiency is increased by utilizing the magnetic bottle effect. This study demonstrates an application to Penning Ionization electron spectroscopy using collisional Ionization with metastable He*(23S) atoms. Technical details and performances of the instrument are presented. This spectrometer can be used for studies of functional molecules and assemblies, and exterior electron densities are expected to be selectively observed by the Penning Ionization.
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Collision-Energy-Resolved Penning Ionization Electron Spectroscopy of Glycine with He(23S) Metastable Atoms: Conformational Isomers in Collisional Ionization
The journal of physical chemistry. A, 2009Co-Authors: Yoshihiro Yamakita, Koichi OhnoAbstract:Conformationally dependent Ionization of the simplest amino acid, glycine, is studied by Penning Ionization electron spectroscopy with velocity-resolved metastable He*(23S) atoms. The observed He I ultraviolet photoelectron and Penning Ionization electron spectra are reproduced by superimposed theoretical spectra, assuming thermal distributions of conformers. The conformations of amino acids are determined by analyzing the observed Penning Ionization cross sections, peak shifts, and collision energy dependences of partial Ionization cross sections (CEDPICS). The Penning Ionization cross sections are governed by collisionally accessible exterior electron densities. When the amino and carbonyl groups are exposed to He* access, the nonbonding orbitals of N (nN) and O atoms (nO) give rise to strong bands. The observed negative peak shifts and negative CEDPICS for the nN and nO orbitals suggest the presence of attractive interactions around their electron distributions. The most attractive wells are estimated ...
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Penning Ionization of [2,2]-paracyclophane by collision with metastable He*(23S) atoms
Chemical Physics Letters, 2000Co-Authors: Yoshihiro Yamakita, Masayo Yamauchi, Koichi OhnoAbstract:Abstract Penning Ionization of [2,2]-paracyclophane (PC) with metastable He*( 2 3 S ) atoms has been studied by means of simultaneous detection of collision energy and electron energy. Negative collision energy dependences of partial Penning Ionization cross-sections have been observed in the range of 115–283 meV. This indicates the presence of an attractive potential well around PC. Assignments of Penning Ionization electron and HeI ultraviolet photoelectron spectra have been made by outer valence Green's function calculations. Molecular-orbital and model-potential calculations have also been performed, and the characteristic features of electron density and interaction potential are discussed in comparison with the case of benzene.
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Penning Ionization of 2 2 paracyclophane by collision with metastable he 23s atoms
Chemical Physics Letters, 2000Co-Authors: Yoshihiro Yamakita, Masayo Yamauchi, Koichi OhnoAbstract:Abstract Penning Ionization of [2,2]-paracyclophane (PC) with metastable He*( 2 3 S ) atoms has been studied by means of simultaneous detection of collision energy and electron energy. Negative collision energy dependences of partial Penning Ionization cross-sections have been observed in the range of 115–283 meV. This indicates the presence of an attractive potential well around PC. Assignments of Penning Ionization electron and HeI ultraviolet photoelectron spectra have been made by outer valence Green's function calculations. Molecular-orbital and model-potential calculations have also been performed, and the characteristic features of electron density and interaction potential are discussed in comparison with the case of benzene.
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Collision energy resolved Penning Ionization electron spectra of polycyclic aromatic hydrocarbons
Journal of Electron Spectroscopy and Related Phenomena, 1998Co-Authors: Masayo Yamauchi, Hideo Yamakado, Yoshihiro Yamakita, Koichi OhnoAbstract:Abstract Penning Ionization of naphthalene and anthracene with He*(23S) atoms has been studied by means of simultaneous detection of collision energy and electron energy. The anisotropy of interaction potentials between He*(23S) atoms and the target molecules has been found on the basis of the collision energy dependences of partial Penning Ionization cross-sections. Based on the analyses of collision energy dependences and electron correlation calculations, assignments of ultraviolet photoelectron spectra are discussed.
P. E. Siska - One of the best experts on this subject based on the ideXlab platform.
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A vibrationally adiabatic theory of molecular Penning Ionization
The Journal of Chemical Physics, 1995Co-Authors: H. M. Bevsek, P. E. SiskaAbstract:Based on available theoretical and experimental information on the Penning Ionization of molecules by metastable helium and neon atoms at thermal energies, an approximate theoretical approach for incorporating the vibrational degrees of freedom is developed. The electronically excited, metastable atoms have diffuse outer orbitals, giving rise to relatively soft intermolecular repulsion in nonbonded excited state potentials. A low‐energy ionizing collision is then near‐adiabatic in respect to its effect on the vibrations of the molecule under attack. In addition for the great majority of experimentally studied molecules, nearly vertical vibrational populations in the Penning molecular ion are observed in Penning Ionization electron spectroscopy (PIES). In the simplest limit of vibrational adiabaticity, the bond oscillator remains unperturbed by the collision, and small deviations from verticality may then be interpreted as a reflection of the bond‐length dependence of the discrete‐continuum coupling that g...
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Molecular-beam studies of Penning Ionization
Reviews of Modern Physics, 1993Co-Authors: P. E. SiskaAbstract:Molecular-beam experiments have exposed a new wealth of detail on the general reaction [ital A][sup *]+[ital B][r arrow][ital A]+[ital B][sup +]+[ital e][sup [minus]] first suggested by Penning in 1927. The new capabilities not available to traditional swarm techniques include mass and electron spectroscopy on the reaction products and angle-resolved measurements of the scattering of both reagents and products. These new results have stimulated the recent development of both the electronic structure and the dynamical theories necessary for a first-principles description of at least the simplest of these reactions, those involving small atomic and diatomic species [ital B]. Recent progress in both experiment and interpretation is critically reviewed, and the prospects for attaining a global understanding of Penning Ionization in larger systems are assessed.
