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  • 1
    Electronic Resource
    Electronic Resource
    Determination of carbon cluster ionization potentials via charge transfer reactions (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 358-363 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ionization potentials (IPs) for carbon clusters containing 6–24 atoms have been determined from charge transfer reactions of carbon cluster ions with compounds of known ionization potential in a Fourier transform ion cyclotron resonance mass spectrometer. Cluster IPs generally decrease with increasing cluster size, but the IPs for clusters containing 4n+3 atoms (n=1–5) are found to be ∼0.5 eV lower than those of neighboring clusters. The relationship between cluster IP and structure is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458437
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  • 2
    Electronic Resource
    Electronic Resource
    Ag7 cluster: Pentagonal bipyramid (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 869-872 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Ag7 metal cluster was formed in a solid neon matrix at 4 K. The identity of the cluster was established via X-band electron-spin-resonance (ESR) spectroscopy, and its structure was found to be a pentagonal bipyramid (D5h symmetry) with a 2A‘2 ground state. Thus its properties are completely analogous to its Group IA alkali-metal counterparts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453241
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  • 3
    Electronic Resource
    Electronic Resource
    Laser photofragmentation and photodesorption of physisorbed CH3Br on lithium fluoride (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 738-744 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Laser irradiation at 193 nm of multilayer of CH3Br physisorbed on LiF at 30 K leads to both photofragmentation and photodesorption of molecules. One-photon photofragmentation was observed leading to broad velocity distributions for ejected CH3 and Br. Fragments as fast as those found in gas-phase photofragmentation were seen as well as collisionally slowed fragments. High energy (2 eV, four times the gas-phase kinetic energy) Br fragments were also observed due to collisions with rebounding CH3. Collisionally ejected molecules were also seen. A small fraction of molecules desorbed via a thermal process, associated perhaps with small amounts of adsorbed particulate contaminants. This mechanism may be responsible for some of the molecular desorption seen by other groups. Thermal desorption studies show that CH3Br (or CO2, Xe, or H2O) does not wet LiF, indicating a general trend important to all alkali–halide overlayer studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452276
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  • 4
    Electronic Resource
    Electronic Resource
    "Magic number'' carbon clusters: Ionization potentials and selective reactivity (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 3556-3562 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ionization potentials (IPs) of several large carbon clusters Cn (n≥48), including the enhanced abundance ("magic number'') clusters C50, C60, and C70, have been determined by Fourier transform ion cyclotron resonance (FTICR) mass spectrometric charge transfer bracketing experiments. The IPs of C50, C60, and C70 were bracketed by the same two charge transfer compounds, leading to a common value of 7.61±0.11 eV. The IPs of even numbered clusters adjacent to these magic number clusters were found to be lower by as much as 0.5 eV and all clusters between C50 and C200 were determined to have IPs greater than 6.20 eV. The reaction rates of C+60 and C+70 with metallocenes were anomalously slow in comparison to the other large carbon cluster ions. IP and reactivity results suggest that C50, C60, and C70 may indeed have different or more stable structures than neighboring clusters, which supports the hypothesis of closed-shell, spherical species. The implications of these results for the mechanism of C+n formation by direct laser vaporization are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459778
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  • 5
    Electronic Resource
    Electronic Resource
    Water-chain clusters: Vibronic spectra of 7-hydroxyquinoline⋅(H2O)2 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1192-1203 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Mass- and isomer-selected S1←S0 resonant two-photon ionization and S1→S0 fluorescence spectra were obtained for the supersonically cooled 7-hydroxyquinoline⋅(H2O)2 cluster. UV/UV-holeburning measurements show that 〉98% of the spectrum is due to a single "water-chain" cluster isomer, although two different tautomers (7-keto- and 7-hydroxyquinoline), two different rotamers (cis- and trans-hydroxy), and two torsional conformers of the chain are possible. Ab initio calculations of structures and vibrations of five different tautomers/ rotamers/ conformers of this cluster are reported. These predict that the cis-7-hydroxyquinoline⋅(H2O)2 "up/down" water-chain form is the most stable cluster. The experimentally observed S0 and S1 state vibrational frequencies agree well with those calculated for this isomer. We find no evidence for either the trans-rotamer or the keto tautomer clusters. S1←S0 excitation leads to contraction of all three hydrogen-bonds along the hydrogen-bonded water chain, inducing intermolecular stretching vibrations, but no proton transfer. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480672
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  • 6
    Electronic Resource
    Electronic Resource
    Vibrational spectroscopy and photodissociation of jet-cooled ammonia (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 4955-4961 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally mediated photodissociation action spectroscopy provides rotation-vibration spectra of jet-cooled ammonia in the 2.3 μm and 3.0 μm regions by detecting the emission of electronically excited NH2(A˜ 2A1) produced by the photodissociation of the vibrationally excited molecules. Vibrational excitation changes the relative photofragmentation yield of NH2(A˜ 2A1) markedly. Isoenergetic photolysis of ammonia molecules with one quantum of antisymmetric N–H stretching excitation (ν3) or two quanta of bend (2ν4) yields three times more excited state NH2(A˜ 2A1) than photolysis of NH3 with a quantum of symmetric N–H stretch excitation (ν1). By contrast, the relative yield is insensitive to initial vibrational excitation of the combination bands ν1+ν2 and ν2+ν3 that contain the umbrella (inversion) motion ν2. The vibrational mode dependence of the NH2(A˜ 2A1) photofragment yield arises from either enhanced Franck–Condon factors for electronic excitation or from an increased probability for the competing nonadiabatic dissociation to form the ground state NH2(X˜ 2B1) product. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1450550
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  • 7
    Electronic Resource
    Electronic Resource
    Semiclassical treatment of charge transfer in molecule-surface scattering (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 6396-6403 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have treated the ionization probability of iodine molecules scattered from diamond by a semiclassical surface hopping scheme, namely Tully's fewest-switches algorithm [J. Chem. Phys. 93, 1061 (1990)]. The interaction is described by a model potential that has been adjusted to empirical data. We start with a one-dimensional two-state model in which just the molecular distance from the surface and the neutral and negatively charged state of I2 are considered. We determine the ionization probability within the adiabatic and diabatic representation and compare it with exact quantum calculations. For this particular problem we find that the diabatic picture shows too little coherence, while the adiabatic representation yields satisfactory results. In the second part we have successively increased the complexity of the simulation by additionally taking a surface oscillator coordinate, the molecular rotation and vibration into account. Including more degrees of freedom damps out the Stückelberg oscillations present in the one-dimensional model. Our results qualitatively reproduce the observed dependence of the ionization probability on the incident energy of the molecules. This dependence is not given by the electronic coupling per se, but rather due to energy transfer to substrate and internal degrees of freedom during the scattering event. Finally, we are also able to reproduce the measured dissociation probability which can be explained in a centrifugal model. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356457
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  • 8
    Electronic Resource
    Electronic Resource
    Water–wire clusters: Vibronic spectra of 7-hydroxyquinoline⋅(H2O)3 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 9032-9043 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The supersonically cooled 7-hydroxyquinoline⋅(H2O)3 cluster was investigated by mass- and isomer-selected S1←S0 resonant two-photon ionization and S1→S0 fluorescence spectroscopy. UV(ultraviolet)/UV-holeburning measurements prove that a single cluster isomer is formed, although different tautomers (7-keto- and 7-hydroxyquinoline), rotamers (cis and trans) and isomers (cyclic and water–wire) are possible. Ab initio calculations of structures and vibrations of different tautomers and isomers of this cluster predict that the cis-enol-7-hydroxyquinoline⋅(H2O)3 "water–wire" cluster is the most stable species. The experimental S0 and S1 inter- and intramolecular vibrational frequencies are in good agreement with the calculated harmonic frequencies. S1←S0 excitation leads to contraction of all four hydrogen bonds along the hydrogen bonded water wire, inducing intense intermolecular stretching vibrations of the O–H(centered ellipsis)O and HO–H(centered ellipsis)N(quinoline) hydrogen bonds which terminate the water–wire. There are no spectroscopic signs of proton transfer. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319352
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  • 9
    Electronic Resource
    Electronic Resource
    Proton transfer in 7-hydroxyquinoline⋅(NH3)n solvent clusters (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 560-565 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Mass- and isomer-selected S1←S0 resonant two-photon ionization and S1→S0 fluorescence spectra were obtained for the supersonically cooled 7-hydroxyquinoline⋅(NH3)n clusters with n=2–16. For n=2 and 3, the absorption and emission spectra exhibit discrete and narrow bands, characteristic of nonreactive hydrogen bonded ammonia-chain clusters. For n≥4, the S1←S0 R2PI spectra are completely broadened, with an onset at (approximate)355 nm. For n=4–7, a weak fluorescence emission is observed, Stokes-shifted by (approximate)185 nm, with a maximum at (approximate)540 nm, which shows discrete structure on a broad background. From comparison to fluorescence emission observed in bulk solution, we conclude that S1 state enol→keto tautomerization occurs. For the n≥7 or 8 clusters, the fluorescence emission spectra become completely unstructured and shift to the blue, peaking at 435–450 nm. This emission indicates the occurrence of either S1-state proton transfer to the ammonia solvent cluster and formation of the 7-HQ anion, or of the ground-state intracluster enol→keto tautomerization reaction. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480548
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  • 10
    Electronic Resource
    Electronic Resource
    Overtone spectroscopy in nitrous oxide (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 5931-5938 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The near infrared and visible absorption spectrum of nitrous oxide 14N216O has been recorded by Fourier transform absorption spectroscopy, between 6500 and 11 000 cm−1, and by Intracavity Laser Absorption Spectroscopy, between 11 700 and 15 000 cm−1. Nineteen new bands are observed and, altogether, 34 cold and 10 hot bands are rotationally analyzed. The related upper term values, vibrational assignments, and principal rotational constants, as well as the relative band intensities are quantitatively discussed in terms of the formation of vibrational clusters, on the basis of the effective Hamiltonian developed by J. L. Teffo, V. I. Perevalov and O. M. Lyulin [J. Mol. Spectrosc. 168, 390 (1994)]. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470473
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