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  • 1
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 33.60.Cv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic structure of an isolated Ca@C60 molecule was probed by photoelectron spectroscopy (PES) of Ca@C 60 − , generated by laser desorption of a preformed Ca@C60/fullerene thin film. The PES spectrum of Ca@C60 was found to be similar to that of C 60 − , except that Ca@C60 has an electron affinity of 3.0 eV, about 0.3 eV higher than that of C60. The spectrum suggests that Ca atom donates its two 4s electrons to the C60 t lu lowest unoccupied molecular orbital. Thus, the interaction between the central Ca atom and C60 is quite ionic, and Ca@C60 can essentially be expressed as Ca2+@C 60 2− .
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The metal-sulphur active sites of hydrogenases catalyse hydrogen evolution or uptake at rapid rates. Understanding the structure and function of these active sites—through mechanistic studies of hydrogenases, synthetic assemblies and in silico models—will help guide the design of ...
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  • 3
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 4
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally resolved photoelectron spectra of MC2− (M=Sc, V, Cr, Mn, Fe, and Co) are reported at two detachment photon energies, 532 and 355 nm. All the spectra showed a well resolved vibrational progression in the ground state detachment features. Electron affinities, vibrational frequencies, and information about the low-lying electronic states were obtained for the first row transition metal dicarbide molecules. The measured electron affinities for the MC2 species show strong metal-dependence with a minimum at VC2 and a maximum at MnC2. The ground state vibrational frequencies were observed to decrease from ScC2 to a minimum in CrC2 and then increases slightly in MnC2 and FeC2. The trends of the electron affinities and vibrational frequencies for the MC2 species were found to correlate well with the corresponding monoxides, suggesting that the chemical bonding in M–C2 is analogous to that in M–O. The M–C2 bonding was thus interpreted to be quite ionic, and MC2 can be qualitatively viewed as M2+C22−, analogous to M2+O2−. © 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 103 (1995), S. 4363-4366 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoelectron spectroscopy of CuO−2 has been studied at three detachment wavelengths: 532 nm, 355 nm, and 266 nm. Vibrationally resolved spectra for two distinct isomers are observed: the Cu(O2) complex and the copper dioxide molecule. The Cu(O)2 complex has an electron affinity (EA) of 1.503 (10) eV with a ground state vibrational frequency of 530 (50) cm−1. Its first electronic excited state is 7400 (300) cm−1 above the ground state. The Cu(O2)− anion is also observed to undergo photodissociation to Cu−+O2 at both 532 nm and 355 nm detachment wavelengths. The copper dioxide molecule is found to have a high EA of 3.46 (4) eV. Three low-lying excited states are observed within 1 eV above the ground state. The first two excited states of the copper dioxide molecule both possess a totally symmetric vibrational frequency of 640 (60) cm−1. © 1995 American Institute of Physics.
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  • 7
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study Ge2O2 and Ge2O−2 with density functional theory (DFT) and photoelectron spectroscopy (PES). We find that Ge2O2 is a rhombus (D2h), closed-shell molecule with a large HOMO-LUMO gap. The PES spectrum of Ge2O−2 is obtained at four detachment photon energies: 1064, 532, 355, and 266 nm. Vibrational structure is resolved at the lowest photon energy with a single progression and a frequency of 400 (60) cm−1. The experimental adiabatic electron affinity is obtained to be 0.625 (0.050) eV for Ge2O2. The calculated vertical and adiabatic electron affinities and the HOMO-LUMO gap are in good agreement with the experimental values. The calculated totally symmetric vibrational mode of Ge2O2 (335 cm−1) is in reasonable agreement with the observed vibration and represents a Ge–Ge breathing motion. © 1995 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
    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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  • 10
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution He i (584 A(ring)) photoelectron spectra of ZnCl2, MnCl2, and NiCl2 were measured using a high temperature supersonic molecular beam source. In ZnCl2, vibrational structures were resolved, and spectroscopic constants were derived for the observed molecular ion states. A single ν1 vibrational progression was observed for the C 2Σ+g state of ZnCl+2. A Franck–Condon factor calculation allowed us to obtain a Zn–Cl equilibrium bond length increase of 0.095(5) A(ring) and a ν1 vibrational frequency of 290(8) cm−1. For the open-shell molecules, MnCl2 and NiCl2, no vibrational structure could be resolved because of their very low bending frequencies. Transitions from the ligand orbital and metal d orbital ionizations were clearly resolved, with those of the d orbitals having considerably narrower band widths. Even though many final states are expected for ionization of the open-shell d orbitals, only a few states were observed. This was explained in MnCl2 by the one-electron spin selection rule: Sf=Si ±1/2. Besides the spin selection rule, a propensity toward high spin was proposed to account for the spectrum of NiCl2. From the metal d orbital and ligand orbital splittings, the degree of covalent bonding was inferred to be in the order of: MnCl2〉NiCl2〉ZnCl2.
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