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  • Articles  (36)
  • 1995-1999  (36)
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  • Articles  (36)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1957-1966 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A magnetic-bottle time-of-flight (TOF) photoelectron spectrometer, coupled with an electrospray ionization source, has been developed for the investigation of multiply charged anions in the gas phase. Anions formed in the electrospray source are guided by a radio-frequency quadrupole ion guide into a quadrupole ion trap, where the ions are accumulated. A unique feature of this apparatus involves the coupling of a TOF mass spectrometer to the ion trap with perpendicular ion extraction. The ion trap significantly improves the duty cycle of the experiments and allows photodetachment experiments to be performed with low repetition-rate lasers (10–20 Hz). This novel combination makes the photodetachment photoelectron spectroscopy studies of multiply charged anions possible for the first time. Furthermore, the perpendicular extraction of ions, pulsed out of the ion trap, to the TOF mass spectrometer allows the ion energies to be conveniently referenced to ground, simplifying the configuration of the TOF mass spectrometer and the subsequent magnetic-bottle TOF photoelectron spectrometer. The mass resolution (M/ΔM) achieved is about 800 for smaller ions. The magnetic-bottle photoelectron spectrometer resolution is about 11 meV full width at half maximum for 0.5 eV photoelectrons with an overall resolution of ΔE/E∼2%. The detailed design, construction, and operation of the new apparatus are presented. © 1999 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 4763-4771 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoelectron spectra of the MX2− (M=Li, Na; X=Cl, Br, I) superhalogen anions have been obtained for the first time. The first vertical detachment energies (VDEs) were measured to be 5.92±0.04 (LiCl2−), 5.86±0.06 (NaCl2−), 5.42±0.03 (LiBr2−), 5.36±0.06 (NaBr2−), 4.88±0.03 (LiI2−), and 4.84±0.06 eV (NaI2−), which are all well above the 3.61 eV electron detachment energy of Cl−, the highest among atomic anions. Experimental photoelectron spectra have been assigned on the basis of ab initio outer valence Green function (OVGF) calculations. The corresponding theoretical first VDEs were found to be 5.90 (LiCl2−), 5.81 (NaCl2−), 5.48 (LiBr2−), 5.43 (NaBr2−), 4.57 (LiI2−), and 4.50 eV (NaI2−), in excellent agreement with the experimental values. Photodetachment from the top four valence molecular orbitals (2σg22σu21πu41πg4) of MX2− was observed. Analysis of the polestrength showed that all electron detachment channels in this study can be described as primarily one-electron processes. © 1999 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 7667-7672 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of the heterodimer AlSi is experimentally studied using anion photoelectron spectroscopy. Four low-lying electronic excited states are observed for AlSi. The electron affinity of AlSi is measured to be 1.32 (5) eV, which is lower than that of both Al2 and Si2. The electronic structure of AlSi is understood by comparing to that of the known Al2 and Al2− molecules. The ground state of AlSi is determined to be X 4Σ− with a vibrational frequency of 400 (50) cm−1. The four excited states are A 2Σ−, B 2Δ, C 2Π, and D 2Σ+ with excitation energies of 0.23, 0.67, 0.82, and 1.13 eV, respectively. The photoelectron spectra of Al2− are also presented and excited states of the Al2− anion are definitively observed. The electronic structure of AlSi is discussed and compared to that of the homonuclear dimers, Al2 and Si2. © 1997 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 4497-4509 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the first observation and photodetachment photoelectron spectroscopic study of a series of hexahalogenometallates dianions MCl62− (M=Re, Os, Ir, and Pt) and MBr62− (M=Re, Ir, and Pt) in the gas phase. All of these species were found to be stable as free gaseous doubly charged anions. Photoelectron spectra of all the dianions were obtained at several detachment photon energies. The photon-energy-dependent spectra clearly revealed the dianion nature of these species and allowed the repulsive Coulomb barriers to be estimated. The binding energies of the second excess electron in MCl62− (M=Re, Os, Ir, Pt) were determined to be 0.46 (5), 0.46 (5), 0.82 (5), and 1.58 (5) eV, respectively, and those in MBr62− (M=Re, Ir, Pt) to be 0.76 (6), 0.96 (6), and 1.52 (6) eV, respectively. A wealth of electronic structure information about these metal complexes were obtained and low-lying and highly-excited electronic states of the corresponding singly charged anions were observed. Detachment from metal d orbitals or ligand orbitals were observed and could be clearly distinguished; detachments from the metal d-orbitals all occur at low binding energies whereas those from the ligand-dominated orbitals all take place at rather high binding energies. We also found a remarkable correlation between electron affinities measured in vacuo and the redox potentials obtained in the solution phase of these species. © 1999 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 3635-3638 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A photodetachment photoelectron spectroscopy study of a doubly charged anion (S2O82−) in the gas phase is reported at three photon energies: 193, 266, 355 nm. Adiabatic and vertical electron binding energies of S2O82− were measured to be 1.7±0.2 and 2.2±0.1 eV, respectively. Several excited states were observed for the S2O8− singly charged anion at 193 nm. The repulsive Coulomb barrier that binds multiply charged anions was clearly shown in the detachment spectra of S2O82−. The effects of the Coulomb barrier to the detachment spectra and electron tunneling through the barrier are presented. The barrier height, which is equivalent to the magnitude of the Coulomb repulsion between the two excess charges in S2O82− was estimated to be ∼3 eV. © 1999 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 449-458 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoelectron spectra of a series of Al3Oy− clusters (y=0–5) are presented at several photon energies: 532, 355, 266, and 193 nm. The electron affinities and low-lying electronic states of the Al3Oy clusters are reported. The photoelectron spectra clearly reveal a sequential oxidation behavior and how the electronic structure of the clusters evolves from that of a metal cluster at Al3 to that of a complete oxide cluster at Al3O5: Two valence electrons of Al3 are observed to be transferred to each additional O atom until Al3O5, where all the nine valence electrons of Al3 are transferred to the five O atoms. The anion, Al3O5−, which can be viewed as (Al3+)3(O2−)5, is found to be a closed shell cluster, yielding an extremely high electron affinity for Al3O5 (4.92 eV). The electron affinities of the remaining clusters are: 1.90 (Al3), 1.57 eV (Al3O), 2.18 eV (Al3O2), 2.80 eV (Al3O3), and 3.58 eV (Al3O4). An electronic excited state of Al3− is also observed at 0.40 eV above the Al3− ground state. Isomers are observed for all the oxide clusters with lower electron affinities. Particularly, vibrational structures are observed for the two isomers of Al3O3−, as well as a photoisomerization process between the two isomers. The structure and bonding of the oxide clusters are discussed based on the experimental data and the known structures for Al3 and Al3O. © 1998 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 8217-8220 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally resolved photoelectron spectra of C60− are reported at three photon energies: 355, 266, and 193 nm. Complicated vibrational structures were observed for the transition to the C60 ground state with both the Ag and Hg modes being active. An extra feature was observed in the energy gap region between the highest occupied and lowest unoccupied orbitals of C60 in the 266 nm spectra only and it was attributed to an autodetachment process. We also report the most accurate measurement of the electron affinity of C60 (2.689±0.008 eV). © 1999 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 400 (1999), S. 245-248 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In neutral atoms and molecules, electrons are kept within their orbitals by attractive electrostatic interactions with positively charged nuclei, with relatively few neutral molecules being able to bind more than one extra electron. For multiply charged molecular anions, dynamic stability plays ...
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  • 9
    Publication Date: 1998-08-31
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 10
    Publication Date: 1999-04-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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