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  • 1
    Electronic Resource
    Electronic Resource
    Electron attachment to isolated nucleic acid bases (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 7792-7794 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Uracil, thymine, and adenine anions were produced in charge-exchange collisions with laser-excited Rydberg atoms. Anion creation rates for uracil and thymine exhibit Rydberg electron energy dependences which are interpreted as due to the creation of both dipole-bound and conventional (valence) anions while only dipole-bound anions are observed for adenine. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471484
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  • 2
    Electronic Resource
    Electronic Resource
    Dipole binding: An experimental test for small cluster structure calculations (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4952-4964 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An experimental method for the discrimination between nearly degenerate isomers of size selected clusters of closed-shell polar molecules is presented. It is based upon electron attachment properties of dipole fields since a minimum value (≈2.5 D) of molecular dipoles is required for electron binding. When neutral clusters are created in different configurations only those with large enough resulting dipole moments bind electrons and give birth to stable anions. These dipole-bound anions have the geometries of their neutral parents which are here calculated within the framework of the exchange perturbation theory as developed by Claverie. Anions are created by Rydberg electron transfer to cold neutral clusters containing up to six molecules of acetonitrile, water, ammonia, or methanol. Structure and dipole moment calculations account well for the "magic'' numbers observed in mass spectra distributions. Detailed comparisons between experimental data and calculated geometries lead to informations on the structure of several isomers of each studied neutral cluster. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469543
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Structure and intermolecular motions of the water dimer anion (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6420-6425 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic and geometrical structures of the water dimer anion are investigated by density functional calculations. Theoretical values of the very weak electron affinities and vertical detachment energies show good agreement with available experimental data. It is predicted that a significant modification of the neutral parent geometry is introduced by the electron attachment process and leads to a large excitation of anion intermolecular modes. The interpretation of field-detachment experiments of (H2O)−2 and (D2O)−2, produced in collisions between laser-excited Rydberg atoms and cold neutral water clusters, confirms the existence of large amplitude low-frequency motions in the anions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472994
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  • 5
    Electronic Resource
    Electronic Resource
    Dissociative electron attachment to gas-phase 5-bromouracil (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 2517-2521 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report measurements of dissociative electron attachment (DEA) to gaseous 5-bromouracil (BrU) for incident electron energies between 0 and 16 eV. Low energy electron impact on BrU leads not only to the formation of a long lived parent anion BrU−, but also various anion fragments resulting from endo- and exo-cyclic bond ruptures, such as Br−, uracil-yl anions, i.e., (U-yl)−, OCN−, and a 68 amu anion tentatively attributed to H2C3NO−. The incident electron energy dependent signatures of either the Br− and (U-yl)− yields (at 0, 1.4, and 6 eV), or the OCN− and H2C3NO− yields (at 1.6 and 5.0 eV) suggests competing DEA channels for anion fragment formation. The production cross sections, at 0 eV incident electron energy, for BrU−, Br−, and (U-yl)− are estimated to be about 6×10−15, 6×10−14, and 1.0×10−15 cm2, respectively. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1306654
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental and theoretical ab initio study of the influence of N-methylation on the dipole-bound electron affinities of thymine and uracil (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11876-11883 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The influence of N-methylation on the dipole-bound electron affinities of pyrimidine nucleic acid bases, uracil and thymine, has been investigated theoretically using ab initio quantum mechanical calculations, and experimentally using Rydberg electron transfer spectroscopy. Both experiment and theory are consistent in showing that replacement of hydrogen atoms by methyl groups reduces electron affinities corresponding to formation of dipole-bound anions of these systems. Also, the distortion of the anion geometries with respect to the geometries of the neutral parents are reduced with the methylation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479175
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  • 7
    Electronic Resource
    Electronic Resource
    Electrons weakly bound to molecules by dipolar, quadrupolar or polarization forces (1998)
    Springer
    The European physical journal 2 (1998), S. 149-156 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 34.50.Gb Electronic excitation and ionization of molecules; intermediate molecular states (including lifetimes, state mixing, etc.) - 36.90.+f Other special atoms, molecules, ions, and clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Within the framework of a simple electrostatic model we here discuss the stability of very weakly bound molecular negative ions. In contrast with the case of conventional valence anions, the excess electron is then located in a very diffuse orbital and is mainly bound by electrostatic dipolar, quadrupolar and polarization forces at large distances from the neutral molecular core. By fitting a single repulsion parameter of the model to the available experimental data, it is possible to make quantitative predictions of the excess electron binding energies in these species. Critical values of dipole moment, quadrupole moment or polarizability required for the observation of stable dipole-bound, quadrupole-bound or polarization-bound negative ions are predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100500050103
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