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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 13748-13754 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    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 111 (1999), S. 1433-1437 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the first vibrationally resolved spectroscopic study of FeO+. We observe the 0←0 and 1←0 bands of a 6Σ←X 6Σ transition at 28 648.7 and 29 311 cm−1. Under slightly modified source conditions the 1←1 transition is observed at 28 473 cm−1. In addition to establishing an upper limit D0o(Fe+–O)≤342.7 kJ/mol, our results give the first experimental measurements of the vibrational frequencies in both the ground state, ν0″=838±4 cm−1, and the excited electronic state, ν0′=662±2 cm−1. Partially resolved rotational structure underlying the vibrational peaks has been analyzed to measure the predissociation lifetime and estimate the change in molecular constants upon electronic excitation. © 1999 American Institute of Physics.
    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 104 (1996), S. 4490-4501 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Oxygen, hydrogen, and chlorine atoms react with vibrationally excited HCN to produce CN and OH, H2, or HCl, respectively. The experiments presented here use direct vibrational overtone excitation to prepare states of HCN having four quanta of C–H stretching excitation [(004) state] or three quanta of C≡N stretching and two quanta of C–H stretching excitation [(302) state] and laser-induced fluorescence to determine the rotational and vibrational states of the CN product. We find that the reaction of HCN with O produces CN having little vibrational and rotational energy, with 85% of the CN in v=0, 12% in v=1, and 3% in v=2. The CN from the reaction of H with HCN is slightly more energetic, with 77% in v=0, 17% in v=1, and 6% in v=2. By contrast, the reaction of Cl with HCN produces CN with a considerable amount of excitation, about 30% is in v=1 and at least 10% is in v=2, depending on the initial vibrational state of the HCN reactant. The enhanced excitation of the CN product of the reaction with Cl reflects the contribution of a different mechanism. We conclude that the O-atom reaction forms CN exclusively by a direct abstraction reaction, the H-atom reaction produces CN primarily by direct reaction at the collisional energies of our experiment, and the Cl-atom reaction forms CN by the dissociation of an intermediate complex in addition to the direct abstraction reaction. © 1996 American Institute of Physics.
    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 86 (1987), S. 2334-2342 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The proton affinity of cyanoacetylene HCCCN was determined by pulsed high pressure mass spectrometric equilibrium measurements as 180.1±1 kcal/mol. Ion cyclotron resonance (ICR) bracketing experiments yielded the proton affinity of diacetylene HCCCCH as 180±1 kcal/mol and of cyanogen NCCN as 161±2 kcal/mol. Ab initio calculations at the 6-31+G** level are used to evaluate the heats of formation of HCCCCH as 105 and of HCCCN as 87 kcal/mol. The ab initio results show also that protonation of diacetylene on a terminal carbon converts a destabilizing antibonding interaction between the triple bonds in the neutral molecule into an attractive interaction, leading to a significant shortening of the C2–C3 bond.
    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 116 (2002), S. 4071-4078 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Specific ion–molecule reactions are used to prepare two intermediates of the FeO++CH4 reaction, and photodissociation of the jet-cooled intermediates is examined in the visible and near-ultraviolet using time-of-flight mass spectrometry. The photodissociation spectrum of the aquo iron carbene complex [H2C(Double Bond)Fe–OH2]+ shows transitions to at least four excited electronic states in the FeCH2+ chromophore, with broad vibrational structure. Photoexcitation of the insertion intermediate [HO–Fe–CH3]+ leads to formation of FeOH++CH3 and also triggers the reaction to produce Fe++CH3OH. The photodissociation spectrum of [HO–Fe–CH3]+ presents a vibrationally resolved band involving progressions in the excited state Fe–C stretch, Fe–O stretch, and O–Fe–C bend. The change in the Fe–C bond length in [HO–Fe–CH3]+ and [H2C(Double Bond)Fe–OH2]+ upon photoexcitation is calculated from a Franck–Condon analysis of the vibronic features observed. The analysis of the experimental results is aided by hybrid Hartree–Fock/density-functional (B3LYP) calculations on [HO–Fe–CH3]+ and [H2C(Double Bond)Fe–OH2]+ performed to determine molecular parameters, and time-dependent density functional theory (TD-DFT) calculations on FeCH2+ to predict excited electronic states. © 2002 American Institute of Physics.
    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 99 (1993), S. 1744-1751 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have determined the branching ratio for the reaction of hydrogen atoms and HOD with either the O–H bond excited or the O–D bond excited. In both cases, the initially excited bond reacts preferentially. Excitation of the third O–H stretching overtone, 4νOH, favors breaking the O–H bond by a factor of ∼200, and excitation of the fourth O–D stretching overtone, 5νOD, favors breaking the O–D bond by a factor of ∼220. Thus vibrational excitation can control the H+HOD reaction to produce either product almost exclusively. A simple model using the calculated wave function for each state and the measured reaction cross section for a particular vibrational excitation predicts the high selectivity observed for the two reactions.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6293-6303 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the bond selected photodissociation of HNCO from a vibrationally excited state containing three quanta of N–H stretch (3ν1) and demonstrate that initial vibrational state preparation strongly influences the photochemical branching in HNCO, producing either NCO (X 2Π) from cleavage of the N–H bond or NH (a 1Δ) from cleavage of the C–N bond. Initial excitation of the N–H dissociation coordinate by excitation of the N–H stretching overtone enhances the probability for breaking the N–H bond in the electronically excited state. Compared to isoenergetic photolysis of the ground vibrational state, photodissociation of the 3ν1 state alters the NCO quantum yield by roughly a factor of 4 at the largest photolysis energy used in this work, changing the channel that breaks the N–H bond from the minor to the major dissociation pathway. In addition, the experiment measures the quantum yields for production of NCO (ΦNCO) in the one-photon dissociation at three different photolysis wavelengths and provides a correction for the influence of photodissociation from vibrationally and rotationally excited states. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 7982-7987 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Previous studies of the hydrogen abstraction from vibrationally excited H2O and HCN by various atoms have probed the vibrational and rotational energy of the product containing the surviving bond to assess the energy disposal and determine the mechanism of the reaction. Estimating the relative translational energy of the products from the Doppler broadening of the probe transitions has allowed the inference of the internal energy of the unobserved product containing the new bond using conservation of energy. The experiments presented here directly measure the vibrational and rotational energy of both the OH product (containing the new bond) and OD product (containing the old bond) from the reaction of O atoms with HOD having four quanta of O–H stretching excitation (4νOH). All of the OH products are vibrationally excited, being formed almost exclusively in ν=2. Nearly all of the OD products are vibrationally unexcited, with 93% in v=0 and only 7% in v=1. The results are consistent with a spectator picture of the reaction in which the new bond receives most of the available energy. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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