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  • 1
    Electronic Resource
    Electronic Resource
    Photodissociation of Kr+n clusters (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3215-3223 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photodissociation of Kr+n (3≤n≤11) cluster ions is observed for the first time in the 565 to 630 nm wavelength range. Kr+3 has a photodissociation cross section of (8.1±0.8)×10−17 cm2 at 612 nm, while Kr+4 and Kr+5 are found to have larger photodissociation cross sections than Kr+3 with a slightly red-shifted spectrum. Only Kr+ is detected as a photofragment of Kr+3, while in the Kr+n (4≤n≤7) experiments, both Kr+2 and Kr+ photofragments are seen. As size n increases from 7 to 11, Kr+ disappears and Kr+3 appears. Laser power studies show that all are single photon photodissociation processes. For higher order Kr+n clusters (4≤n≤7) the intensity ratio between the two photodissociation products Kr+2 and Kr+ is dependent on the wavelength of the laser light used in the photodissociation, but independent of the polarization direction of the laser. Translational energy analysis of the photofragments is used to investigate the photodissociation mechanisms. In contrast to the photodissociation of Kr+3, where two types of Kr+ photofragments with different values of translational energy release are observed, only one type of Kr+2 photofragment, with zero kinetic energy release is found in the Kr+4 photodissociation. These findings are discussed in terms of the dynamics of photodissociation and possible structures of these cluster ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458854
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  • 2
    Electronic Resource
    Electronic Resource
    Photoelectron spectroscopy of alkali metal tetramer anions: The anomalous spectrum of Li−4 (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2653-2656 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the photoelectron spectrum of Li−4. This spectrum displays a spectral pattern that is strikingly different from that of the other alkali tetramer anions. Using the photoelectron spectrum of Li−4 along with our previously measured photoelectron spectra of Na−4, K−4, and Rb−4 plus other existing evidence, we find that Li−4 does not have a linear geometry, as do the tetramer anions of sodium, potassium, and rubidium. This observation indicates that for both anions and neutrals, lithium clusters appear to take on higher dimensional structures at smaller sizes than do sodium and probably other alkali clusters. By examining the clues found in its photoelectron spectrum, we then speculate as to what the structure of Li−4 may be and also summarize the present state of theoretical progress on this problem. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468696
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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of the X 2Σ+–A 2Π splitting in CsO via photoelectron spectroscopy of CsO− (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3358-3360 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the photoelectron spectrum of CsO−, recorded using 2.540 eV photons. This spectrum provides a direct measurement of the X 2Σ+–A 2Π energy splitting in CsO, which is found to be 0.135±0.025 eV. This work also establishes that the ground state of CsO− is 1Σ+. In addition, the adiabatic electron affinity of CsO is found to be 0.273±0.012 eV, while the D0 value for the X 1Σ+ state of CsO− (with respect to Cs+O−) is found to be 1.84±0.15 eV. Molecular parameter estimates for CsO− are also extracted from the spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466428
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  • 4
    Electronic Resource
    Electronic Resource
    The dipole bound-to-covalent anion transformation in uracil (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 8-11 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nucleic acid base anions play an important role in radiation-induced mutagenesis. Recently, it has been shown that isolated (gas-phase) nucleobases form an exotic form of negative ions, namely, dipole bound anions. These are species in which the excess electrons are bound by the dipole fields of the neutral molecules. In the condensed phase, on the other hand, nucleobase anions are known to be conventional (covalent) anions, implying the transformation from one form into the other due to environmental (solvation) effects. Here, in a series of negative ion photoelectron spectroscopic experiments on gas-phase, solvated uracil cluster anions, we report the observation of this transformation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475360
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  • 5
    Electronic Resource
    Electronic Resource
    Dipole bound, nucleic acid base anions studied via negative ion photoelectron spectroscopy (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 7788-7791 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The anions of the nucleic acid bases, uracil and thymine, were studied by negative ion photoelectron spectroscopy. Both monomer anions exhibit spectroscopic signatures that are indicative of dipole bound excess electrons. The adiabatic electron affinities of these molecules were found to be 93±7 meV for uracil and 69±7 meV for thymine. No conventional (valence) anions of these molecules were observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471482
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  • 6
    Electronic Resource
    Electronic Resource
    On the binding of electrons to nitromethane: Dipole and valence bound anions (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 3472-3478 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Conventional (valence) and dipole-bound anions of the nitromethane molecule are studied using negative ion photoelectron spectroscopy, Rydberg charge exchange and field detachment techniques. Reaction rates for charge exchange between Cs(ns,nd) and Xe(nf ) Rydberg atoms with CH3NO2 exhibit a pronounced maximum at an effective quantum number of n*≈13±1 which is characteristic of the formation of dipole-bound anions [μ(CH3NO2)=3.46 D]. However, the breadth (Δn≈5, FWHM) of the n-dependence of the reaction rate is also interpreted to be indicative of direct attachment into a valence anion state via a "doorway'' dipole anion state. Studies of the electric field detachment of CH3NO−2 formed through the Xe(nf ) reactions at various n values provide further evidence for the formation of both a dipole-bound anion as well as a contribution from the valence bound anion. Analysis of the field ionization data yields a dipole electron affinity of 12±3 meV. Photodetachment of CH3NO−2 and CD3NO−2 formed via a supersonic expansion nozzle ion source produces a photoelectron spectrum with a long vibrational progression indicative of a conventional (valence bound) anion with a substantial difference in the equilibrium structure of the anion and its corresponding neutral. Assignment of the origin (v′=0, v″=0) transitions in the photoelectron spectra of CH3NO−2 and CD3NO−2 yields adiabatic electron affinities of 0.26±0.08 and 0.24±0.08 eV, respectively. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472993
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of theX 2 ∑ u + state of7Li 2 − via negative ion photoelectron spectroscopy (1994)
    Springer
    The European physical journal 29 (1994), S. 209-212 
    Details
    ISSN: 1434-6079
    Keywords: 33.60.−q ; 35.20.Dp ; 35.20.Gs ; 35.20.Vf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The negative ion photoelectron spectrum of7Li 2 − is reported at 488 nm (2.540 eV). Three electronic bands are observed in this spectrum and are assigned to the following photodetachment transitions:7Li2,X 1 ∑ g + +e − ←7Li 2 − ,X 2 ∑ u + ;7Li2,a 3 ∑ u + +e − ←7Li 2 − ,X 2 ∑ u + ; and7Li2,A 1 ∑ u + +e − ←7Li 2 − ,X 2 ∑ u + . The electron affinity of7Li2 is determined to be 0.437±0.009 eV, leading to an anion dissociation energy,D 0, of 0.865±0.022 eV for the ground state of7Li 2 − . A Franck-Condon analysis of the7Li2,X 1 ∑ g + +e − ←7Li 2 − ,X 2 ∑ u + band yields the following spectroscopic constants for the ground state of7Li 2 − :B e =0.502±0.005 cm−1,r e =3.094±0.015 Å, and ω e =232±35 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437139
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  • 8
    Electronic Resource
    Electronic Resource
    An investigation of catalytic activity in mixed metal oxide nanophase materials (1993)
    Springer
    The European physical journal 26 (1993), S. 46-50 
    Details
    ISSN: 1434-6079
    Keywords: 82.65.Jv ; 81.20.Lb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present preliminary evidence for catalytic activity by unsupported mixed metal oxide nanocrystalline materials. The results of this study show that a nanophase form of Li-MgO has begun to exhibit catalytic activity by 300 °C. This is at least 200 degrees below the temperature at which conventional Li-MgO catalysts exhibit comparable activity. Furthermore, at higher temperatures, the same nanophase composition shows enhanced activities and somewhat improved hydrocarbon selectivities over conventional Li-MgO catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01429104
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