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  • 1
    Electronic Resource
    Electronic Resource
    The zero kinetic energy photoelectron spectrum of the propargyl radical, C3H3 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2575-2578 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the zero kinetic energy photoelectron spectrum of the propargyl radical, C3H3. From the spectrum an ionization energy of 69 953±10 cm−1 (8.673 eV) is deduced. Vibrational frequencies are obtained for the totally symmetric normal modes of the propargyl cation, as well as some combination and overtone bands. Both the frequencies and the relative intensities agree well with the predictions from recent ab initio calculations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480830
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  • 2
    Electronic Resource
    Electronic Resource
    Time-resolved photoelectron spectroscopy of the allyl radical: The lifetimes of the ultraviolet bands (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 5812-5822 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report [1+1′] picosecond time-resolved pump–probe photoelectron spectra of the UV bands of the allyl radical. The experiments are performed in a molecular beam of allyl radicals, generated by supersonic jet flash pyrolysis. Photoelectron spectroscopy in a magnetic bottle is shown to be a suitable method for investigating the photophysics of organic radicals. Lifetimes were obtained for all vibronic bands between 250 and 238 nm previously assigned by MPI spectroscopy to the electronically excited B 2A1, C 2B1, and D 2B2 states, with values ranging from 20 ps to 9 ps. The nonradiative decay is due to internal conversion to the electronic ground state. Information on the structure of the allyl cation is deduced from the photoelectron spectrum. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477203
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  • 3
    Electronic Resource
    Electronic Resource
    Photodissociation dynamics of the propargyl radical (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 3441-3448 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photochemistry and photodissociation dynamics of the propargyl radical, C3H3, upon UV excitation is investigated by time- and frequency-resolved detection of hydrogen atoms. From a statistical analysis of the data, we conclude that formation of cyclopropenylidene, c-C3H2, is the dominant reaction channel. Around 22% of the excess energy is released into the translational degrees of freedom. By varying the excitation energy between 265 and 240 nm, microcanonical rates for the loss of a hydrogen atom can be obtained as a function of excess energy. The experimental rates, on the order of several 106 s−1, are in good agreement with Rice–Ramsperger–Kassel–Marcus (RRKM) calculations, provided a scaling factor is used for the vibrational frequencies, to account for the effects of anharmonicity. The interpretation is confirmed in experiments using monodeuterated propargyl radicals, H2CCCD, indicating a mechanism that proceeds via an initial [1,2] H-shift, followed by cyclization. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479629
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  • 4
    Electronic Resource
    Electronic Resource
    Photodissociation dynamics of the allyl radical (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 1450-1462 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photochemistry and photodissociation dynamics of the allyl radical upon ultraviolet (UV) excitation is investigated in a molecular beam by using time- and frequency-resolved photoionization of hydrogen atoms with Lyman-α-radiation. The UV states of allyl decay by internal conversion to the ground state, forming vibrationally hot radicals that lose hydrogen atoms on a nanosecond time scale. Two channels are identified, formation of allene directly from allyl, and isomerization from allyl to 2-propenyl, with a subsequent hydrogen loss, resulting in both allene and propyne formation. The branching ratio is between 2:1 and 3:1, with direct formation of allene being the dominant reaction channel. This channel is associated with site-selective loss of hydrogen from the central carbon atom, as observed in experiments on isotopically labeled radicals. Ab initio calculations of the reaction pathways and Rice–Ramsperger–Kassel–Marcus (RRKM) calculations of the rates are in agreement with the mechanism and branching ratios. From the measured Doppler profiles a translational energy release of 14±1 kcal/mol is calculated. The calculated value of 66 kcal/mol for the barrier to the 1,2 hydrogen shift from allyl radical to 2-propenyl is confirmed by the experimental data. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478020
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  • 5
    Electronic Resource
    Electronic Resource
    Microcanonical rates for the unimolecular dissociation of the ethyl radical (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 5485-5488 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report results on the photodissociation dynamics of the ethyl radical, C2H5. A beam of internally cold radicals is generated by supersonic jet flash pyrolysis of ethyl iodide or n-propylnitrite, respectively. Upon excitation into the A 2A13s Rydberg state ethyl dissociates, presumably on the ground-state surface, into ethylene and a hydrogen atom that is detected by time-resolved photoionization. By varying the excitation energy between 264 and 245 nm, microcanonical rates are obtained as a function of excitation energy. The reaction rates are on the order of 107 s−1, several orders of magnitude slower than expected from simple Rice–Ramsperger–Kassel–Marcus calculations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478445
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  • 6
    Electronic Resource
    Electronic Resource
    The nonradiative decay of the allyl radical excited B 2A1 state studied by picosecond time-resolved photoelectron spectroscopy (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 8197-8200 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nonradiative decay rates of the vibrational ground state and the υ7 fundamental in the electronically excited B 2A1 state of the allyl radical, C3H5, are studied by picosecond time-resolved pump-probe photoelectron spectroscopy. The states decay by internal conversion with a time constant of 20 and 16 ps, respectively. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475121
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics and dynamics in the photodissociation of the allyl radical (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 3329-3332 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The direct observation of the products, kinetics and translational energy release from the photodissociation of the allyl radical, C3H5, upon excitation in the near-uv is reported. A statistical analysis of the data shows that they are in agreement with allene formation being the dominant H-loss reaction channel. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474704
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  • 8
    Electronic Resource
    Electronic Resource
    Space charge and plasma effects in zero kinetic energy (ZEKE) photoelectron spectroscopy (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 5310-5318 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In photoelectron spectroscopy experiments it is generally assumed that the Coulomb force between charged particles is small compared with external fields, and that the free kinetic electrons will quickly leave the ions. This is the basis of the ZEKE photoelectron spectroscopy. However as the density of charged particles is increased, plasma physics effects begin to become important, and the kinetic electrons become trapped by the net positive charge and move so as to set up a self-field which can cancel any externally imposed electric fields. For high densities, fewer electrons than expected are able to escape the self-field. The production of self-consistent electric fields is studied by means of particle-in-cell plasma simulations and by N-body trajectory calculations, and simple expressions are derived for when plasma physics effects become significant. An experimental illustration of plasma effects in ZEKE is presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474241
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  • 9
    Electronic Resource
    Electronic Resource
    Resonance enhancement effects in coherent two-photon ionization of CH3I (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 733-736 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: One-color two-photon zero kinetic energy (ZEKE)-spectra of CH3I were obtained via an intermediate resonant state. In contrast to one-photon spectra an intense progression in the totally symmetric C–I stretching mode ν3+ is observed. The observation can be explained by a resonant-Raman like enhancement in the intermediate dissociative state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465746
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  • 10
    Electronic Resource
    Electronic Resource
    The nonresonant two-photon zero kinetic energy photoelectron spectrum from the electronic ground state of H2S (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 3592-3599 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nonresonant two-photon (1+1) ZEKE (zero kinetic energy) photoelectron spectrum from the X˜ 1A1 electronic ground state of H2S is reported. Complete rotational resolution of the X˜ 2B1 ground state of the ion was achieved for different temperatures in the jet. The ZEKE spectra show angular momentum transfer up to ΔN=2. The rotationalNKa+Kc++ ← J″Ka″Kc″ branching ratios for the low-lying rotational levels were determined. The strongest transitions are those with ΔKa=Ka+−Ka″=±1 and ΔKc=Kc+−Kc″=0 (type c transitions) but transitions with ΔKa=0 and ΔKc=±1 (type a transitions) also show a surprisingly high intensity. Changes in Ka or Kc up to ±3 are observed. The two-photon spectra are compared with those obtained via one-photon VUV photoionization by other authors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464036
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