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  • 1
    Electronic Resource
    Electronic Resource
    Spectroscopy and electron detachment dynamics of C−4, C−6, and C−8 (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 4905-4919 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Resonant multiphoton detachment spectroscopy has been used to obtain vibrationally resolved spectra of the C 2Π←X 2Π electronic transitions in C−4, C−6, and C−8. Transitions due to vibrational excitations in the totally symmetric stretching modes as well as the bending modes are observed. The electron detachment dynamics subsequent to multiphoton absorption are studied by measuring the electron emission time profiles and electron kinetic energy distributions. The observation of delayed electron emission combined with the form of the electron kinetic energy distributions indicates that these species undergo the cluster equivalent of thermionic emission. This interpretation is supported by comparing the experimental results to a microcanonical model for cluster thermionic emission. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472341
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  • 2
    Electronic Resource
    Electronic Resource
    Anion photoelectron spectroscopy of B3N− (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 10491-10500 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally resolved negative ion photoelectron spectra of B3N− at 355 and 266 nm are presented. Two intense bands are observed with adiabatic detachment energies (ADEs) of 2.923±0.008 eV and 3.063±0.008 eV and markedly different photoelectron angular distributions. Aided by electronic structure calculations, the two bands are assigned to transitions from the linear X˜ 4Σ− state of B3N− to the linear 3Π and 5Σ− electronically excited states of neutral B3N, with all three states having a B–N–B–B structure. Weak signal observed at lower electron binding energies is tentatively assigned to two additional linear-to-linear transitions from the low-lying electronically excited 2Π state of B3N− to the 1Σ+ and 3Π states of neutral B3N. Based on these assignments the electron affinity of linear B–N–B–B is 2.098±0.035 eV. It remains uncertain if the 1Σ+ state of linear B–N–B–B or the 3A1 state of cyclic B3N is the overall ground state. At the highest level of theory used here, CCSD(T)/aug-cc-pVTZ, the 1Σ+ state is predicted to lie 0.09 eV below the 3A1 state. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480402
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  • 3
    Electronic Resource
    Electronic Resource
    Anion photoelectron spectroscopy of B2N− (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 8838-8851 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally resolved 355 and 266 nm anion photoelectron spectra of B2N are presented. Photodetachment to two electronic states of linear B–N–B is observed and, aided by electronic structure calculations, assigned to the X˜ 1Σg+→X˜ 2Σu++e− and X˜ 1Σg+→A˜ 2Σg++e− transitions. The electron affinity of B2N is 3.098±0.005 eV and the A˜ 2Σg+ term energy T0 is 0.785±0.005 eV. Observation of excitations involving uneven quanta of the antisymmetric stretching mode (v3) indicates a breakdown of the Franck–Condon (FC) approximation and results from Herzberg–Teller vibronic coupling between the X˜ 2Σu+ and A˜ 2Σg+ states involving the v3 mode. Measurement of the angular dependence of the photodetached electrons serves as a sensitive probe for the identification of these FC forbidden transitions. A linear vibronic coupling model qualitatively reproduces the perturbed v3 potentials of the X˜ and A˜ states. Artifactual symmetry breaking along the v3 coordinate is observed in the ab initio wave functions for the neutral ground state up to the coupled-cluster level of theory, even when Brueckner orbitals are used. No evidence is found for an energetically low-lying cyclic state of B2N, which has been invoked in the assignment of the matrix infrared spectrum of B2N. However, the matrix infrared data agrees well with the peak spacing observed in the photoelectron spectra and reassigned to the linear X˜ 2Σu+ ground state. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480230
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  • 4
    Electronic Resource
    Electronic Resource
    Vibrationally resolved photoelectron spectroscopy of silicon cluster anions Sin− (n=3–7) (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1395-1406 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoelectron spectra of Sin− (n=3–7) have been measured at several photodetachment energies. The anions were created using a pulsed discharge source, resulting in considerably colder clusters than in earlier work. As a result, vibrationally resolved spectra were obtained for larger clusters and more electronic states than in previous studies of these species, leading to more accurate electron affinities, term energies, and vibrational frequencies for the ground and excited electronic states of the neutral clusters. The assignments of excited states were aided by ab initio calculations and photoelectron angular distributions. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475511
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  • 5
    Electronic Resource
    Electronic Resource
    Photodissociation of triplet and singlet states of the CCO radical (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4070-4078 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The triplet and singlet states of the ketenylidene (CCO) radical are investigated using fast radical beam photofragment translational spectroscopy, in which CCO is generated by laser photodetachment of CCO− and subsequently photodissociated, and anion photoelectron spectroscopy. In the photodissociation experiment, two bands in which the upper state of CCO predissociates are studied. Photodissociation from excitation of the A˜ 3Π–X˜ 3Σ− band in CCO is observed from 16 666–23 529 cm−1; resonances are observed and assigned to excited vibrational levels involving all three vibrational modes. We also report the first observation of the c˜ 1Π–a˜ 1Δ band in CCO. Here, the a˜ 1Δ state of CCO is generated by laser photodetachment at higher photon energy than was used to generate the X˜ 3Σ state. The c˜ 1Π state is approximately located by photoelectron spectroscopy of CCO−, and the photodissociation experiment shows that the origin of the c˜ 1Π–a˜ 1Δ band occurs around 17 170 cm−1. Kinetic-energy release spectra from both bands yield accurate values for the C–CO bond dissociation energy and heat of formation of CCO: D0(C–CO)=2.24±0.02 eV (51.7±0.5 kcal/mol) and ΔHf,2980(CCO)=4.04±0.02 eV (91.1±0.5 kcal/mol). Although the translational-energy distributions resulting from excitation to the A˜ 3Π and c˜ 1Π states are clearly nonstatistical, consideration of the potential-energy surfaces indicates that dissociation from both states occurs via radiationless transitions to the X˜ 3Σ− state. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475839
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  • 6
    Electronic Resource
    Electronic Resource
    Photoelectron spectroscopy of SinH− (n=2–4) anions (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 7645-7652 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally resolved photoelectron spectra of SinH− (n=2–4) have been measured at a photodetachment wavelength of 355 nm (3.493 eV). The electron affinities of Si2H, Si3H, and Si4H are 2.31±0.01, 2.53±0.01, and 2.68±0.01 eV, respectively. Vibrational frequencies for the neutral ground states and a low-lying state of Si2H are also determined. Assignment of the electronic states and vibrational frequencies is facilitated by comparison with ab initio calculations. The calculations show that the H atom in Si4H and Si4H− is bonded to a single Si atom, in contrast to the bridged structures found for the smaller clusters. These calculations, along with photoelectron energy and angular distributions, yield a definitive assignment of the ground and nearly degenerate first excited states of Si2H. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476200
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  • 7
    Electronic Resource
    Electronic Resource
    Photoelectron spectroscopy of C4−, C6−, and C8− (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 3428-3436 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoelectron spectra of C4−, C6−, and C8− were obtained at two photodetachment wavelengths, 266 nm (4.657 eV) and 213 nm (5.822 eV). The spectra reveal considerably more electronic and vibrational structure than was seen in previous studies of these species [D. W. Arnold et al., J. Chem. Phys. 95, 8753 (1991)]. Term values for several low-lying excited electronic states of the neutral carbon clusters have been obtained, as well as new vibrational frequencies for the ground and some of the excited electronic states of the neutral clusters. The assignments of excited electronic states were aided by measurements of the photoelectron angular distributions. A new assignment of the vibrational frequencies for C6 is in considerably better agreement with ab initio results than our original assignment. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474715
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of the I3 radical by anion photoelectron spectroscopy (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7607-7609 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ground and first excited states of the I3 radical are characterized by photoelectron spectroscopy of I3− and Ar⋅I3− at 266 nm. The electron affinity of I3 is 4.226±0.013 eV. Based on the recently determined bond dissociation energy of I3−, the I3 ground state is bound by 0.143±0.06 eV. The first excited state of I3 lies 0.27 eV above the ground state. A vibrational progression is seen in the ground state band of the I3− photoelectron spectrum. The addition of an argon atom to I3− reduces the contribution of hot bands to the photoelectron spectrum, facilitating the interpretation of the vibrational structure. Simulations indicate that the I3 ground state is linear with a symmetric stretch frequency of 115±5 cm−1 and is likely to be centrosymmetric. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478672
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of the I2− anion ground state using conventional and femtosecond photoelectron spectroscopy (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 7613-7619 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The X˜ 2Σu+ state of the I2− anion has been fit to a Morse potential using data from two techniques: conventional and femtosecond photoelectron spectroscopy (FPES). Conventional photoelectron spectroscopy is used to determine the adiabatic electron affinity of I2 as well as the well depth and equilibrium nuclear geometry of I2−. In the FPES experiment, the pump pulse induces coherent nuclear motion on the ground state of I2− by resonant impulsive stimulated Raman scattering (RISRS), and the vibrational frequency of the anion is determined from the resulting oscillatory structure in the time-dependent photoelectron spectra. We find the electron affinity (EA) of I2 to be 2.524±0.005 eV, the well depth (De) for I2− to be 1.014±0.005 eV, the equilibrium internuclear separation (Re) to be 3.205±0.005 Å, and the vibrational frequency to be 110±2 cm−1. These values for the I2− potential parameters differ significantly from previous results. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475110
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  • 10
    Electronic Resource
    Electronic Resource
    Anion photoelectron spectroscopy of I2− and I2−⋅Arn (n=1–14, 16, 20) clusters (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 4389-4395 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the mass-selected anion photoelectron spectra of I2− and the weakly bound clusters I2−⋅Arn (n=1–14, 16, 20) measured at a photon energy of 4.657 eV. The experiment yields size-dependent vertical and adiabatic detachment energies for the formation of the ground state and five valence-excited states of the neutral cluster, which correspond to the 1∑g+ (X), 3Π2u (A′), 3Π1u (A), 3Π0−u (B′), 1Π1u (B″), and 3Π0+u (B) states of bare I2. The detachment energies are successively blue-shifted with increasing cluster size, indicating a stronger stabilization of the anionic cluster relative to the neutral counterpart. The blue shift is of similar extent for the electronically excited states A′ and A and approximately 10% less for the X state. The I2− and I2−⋅Ar spectra are simulated employing a Franck–Condon analysis, from which we estimate the ion vibrational temperature and determine the I2−–Ar binding energy (D0=53±4 meV). The results are discussed with respect to possible cluster geometries and the evolution of the total and stepwise solvation energies. For I2−⋅Ar6 we present evidence that all Ar atoms are bound around the waist of the I–I bond. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477042
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