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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3532-3538 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the absolute rates of internal conversion and of intersystem crossing in isoquinoline excited to its S2 vibronic states (3131–3062 A(ring)) in supersonic beams. The combination of direct detection of the triplets, absorption and excitation spectra allowed us to extract these rates. The intersystem crossing rate barely depends on the excess vibrational energy in the S2 manifold, being about 2×109 s−1. The internal conversion rates grow by more than two orders of magnitude over the range of 0–800 cm−1 of excess vibrational energy in the S2 state, up to 5×1010 s−1. At the S2 electronic origin intersystem crossing is the dominant nonradiative channel, while at vibrational energy exceeding 400 cm−1 internal conversion becomes dominant.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7331-7339 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The decay rates of optically excited triplet states of pyrazine in supersonic expansion were measured by using three different methods. The excess energy dependence of the radiationless rate constants in the energy range between the T1 and the S1 electronic origins of the isolated molecule was explored. Decay rates between 7×102 –2.5×104 s−1 were found in the 1500 cm−1 range of excess vibrational energy from the origin of the T1 state. The decay rates are free of mode specificity and rotational effects. The pure radiative lifetime in the measured range is rovibronic independent. The results support a model which suggests that certain vibrational modes, those which undergo large frequency changes in the excited state, control the strong vibrational energy dependence of the T1 →S0 intersystem crossing of pyrazine.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4127-4138 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Efficient excited-state proton transfer in neutral acid–base clusters α-naphthol⋅Bn has been detected and studied by a combination of laser spectroscopic techniques (resonant two-photon ionization, fluorescence excitation, and emission spectroscopy). S1 state proton transfer was observed for B=NH3 and n≥4, as evidenced by several criteria: (a) large red shift and substantial broadening of the R2PI spectra of the n≥4 clusters relative to those of the bare α-naphthol and smaller clusters; (b) very large Stokes shift (∼8000 cm−1) of the emission spectra of the n≥4 clusters; (c) complete broadening of the fluorescence emission band for the n≥4 clusters; and (d) a striking similarity of the emission band position and width of the latter spectra to the emission spectrum of the α-naphtholate anion in basic aqueous solution. No proton-transfer reaction was observed for small solvent clusters with B=NH3 and n≤3, nor for any of the pair complexes studied, which involve a single base partner [B=triethylamine, 3-dimethylamino-1-aminopropane, 1,4-bis(dimethylamino)butane] which we have studied so far. This behavior illustrates the difficulty of achieving charge separation in neutral gas-phase complexes or clusters. A critical gas-phase proton affinity PAcrit =248±3 kcal/mol was determined for proton transfer to take place in the α-naphthol⋅Bn (or base B) system.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 9344-9353 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the photoelectron-spectra of Cl−, Br−, and I−, solvated in water clusters-(H2O)n, where n is 1–7, 1–16, and 1–60, respectively, taken with 7.1 eV photon energy. The vertical binding energies of the solvated anions are used to extract the solvent electrostatic stabilization energies of the anion. The photoelectron spectra of the solvated I− indicate the formation of the first solvation layer with a coordination number of six. Ab initio calculations support solvation shell closure at n=6. This conclusion is not born-out by current molecular dynamics calculations. These calculations favor structures with a surface solvated anion (coordination number of 3–4) and reproduce (within 0.2 eV) our vertical binding energies. The fitting of the experimental binding energies of large I−(H2O)n to the models of classical electrostatic solvation is consistent with surface solvation. In the size range n=34–40 we have detected special cluster structures, with very low electrostatic stabilization. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3649-3655 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the intersystem crossing (ISC) rates of optically excited triplet pyrazine-d4 in supersonic expansion. ISC rates ranging from 3.3×102 to 1.3×103 were found in the 1154 cm−1 range of excess vibrational energy above the T1 origin. These rates were substantially lower than the ISC rate of pyrazine. Our measurements were accompanied by model calculations of the ISC rates of pyrazine and pyrazine-d4. According to this model, certain vibrational modes, which undergo large frequency reduction in the excited state, regulate the strong vibrational energy dependence of the T1→S0 ISC of pyrazine. The large frequency changes result from the interaction of the near lying 3nπ* and 3ππ* states (the "proximity effect''). These calculations account quantitatively for the excess vibrational energy dependence of the ISC rates in pyrazine, as well as for the isotopic substitutional effect.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 9416-9419 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the photoelectron spectra of clusters of I- solvated in water up to fifteen water molecules. The vertical binding energy of the electron increases with cluster size and levels off in clusters containing more than six water molecules. These results strongly indicate that the first solvation layer around the ion consists of six water molecules. This picture is quantitatively consistent with the photoelectron spectroscopy result of I- solvated in bulk water.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 3550-3553 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 7154-7164 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 2675-2685 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the photoelectron spectra of Cl−, Br−, and I− solvated in acetonitrile clusters (CH3CN)n with n=1–33, 1–40, and 1–55, respectively, taken with 7.9 eV photon energy. Anion–solvent electrostatic stabilization energies are extracted from the measured vertical electron binding energies. The leveling of stabilization energies beyond n=10–12 for the three halides signifies the completion of the first solvation layer. This is different from the behavior of anion–water clusters which probably do not fill the first solvation layer, but rather form surface solvation states. Classical molecular dynamics simulations of halide–acetonitrile clusters reproduce the measured stabilization energies and generate full solvation shells of 11–12, 12, and 12–13 solvent molecules for Cl−, Br−, and I−, respectively. Ordered shell structures with high stability were found for the clusters of Cl−, Br−, and I− with n=9, 9, and 12. This special stability is reflected in the intensity distribution of the clusters in the mass spectra. Larger anion–acetonitrile clusters have the molecules beyond the first solvation layer packed in a small droplet which is attached to the first layer. It is suggested that in general, anions solvated in large clusters of polar solvents, might be located close to their surface. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 6288-6297 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a comprehensive experimental study of bound excited states in I−Xen clusters (n=1–54), using photoelectron spectroscopy and energy-dependent action spectroscopy. Starting at n=4, the electron detachment action spectra developed peaks lying in energy lower than the vertical binding energy. This behavior has been shown for both final spin states of the neutral iodine. It indicates the existence of bound electronic states extended over the xenon cluster. The peaks lying in energy below the J=1/2 detachment continuum of the iodine (n〉4) were detected over the whole cluster size range of I−Xen using electron detachment action spectroscopy. For the bound states relating to the J=3/2 continuum, in the size range n=4–12, thermionic emission has marked the existence of bound states. For n〉12, these states were stabilized and detected via two-photon excitations. The picture, unveiled from the above photoelectron and action spectra, is the gradual evolution of bound excited states on the xenon solvent cluster. The critical size for the binding of an excited electron is n=4. At the largest cluster interrogated, I−Xe54, the binding energy amounts to 170 meV. We compare these states to the ground electronic state of Xen− clusters, and discuss the differences between the experiments and model calculations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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