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  • 1985-1989  (15)
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  • 1
    Digitale Medien
    Digitale Medien
    Primary energy distribution in the products of the reaction F + HBr .fwdarw. HF(v') + Br (1986)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 90 (1986), S. 3110-3116 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100405a016
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  • 2
    Digitale Medien
    Digitale Medien
    On the dynamics of abstraction, insertion, and addition-elimination reactions in the gas phase (1988)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 92 (1988), S. 18-27 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100312a008
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  • 3
    Digitale Medien
    Digitale Medien
    A multisurface DIM trajectory study of the reaction: O(1Dg)+H2(X 1Σ+g)→OH(X 2Π)+H(2S) (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3629-3637 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The diatomics-in-molecules method has been used to compute potential energy surfaces for the interactions between O(1Dg) atoms and hydrogen molecules, and a multisurface quasiclassical trajectory study of the reaction dynamics for collisions at several different reagent translational energies has been carried out using these potentials. The multisurface nature of the problem was explicitly included by using a surface-hopping computational technique, based on Landau–Zener transition probabilities, which made all of the relevant surfaces available to the trajectory. The product energy distributions predicted by three slightly different DIM models of these surfaces are computed. In all cases, the dynamics of the reactions which begin on the first excited surface are dramatically different from those of reactions which occur on the lowest surface, the only one which was considered in all previous dynamical calculations on this system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.453913
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  • 4
    Digitale Medien
    Digitale Medien
    The interaction of O(1D2) with HCl: The initial vibrational distributions in the OH(2Π) produced by chemical reaction, and the HCl(1Σ+) produced by E–V energy transfer (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 985-992 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The initial vibrational distributions in both energetically accessible channels of the reaction between O(1D) atoms and HCl molecules are reported. The measurements were made using very fast time-resolved Fourier transform spectroscopy to observe the emission spectra of the products before their vibrational populations could be altered by collisional relaxation. Both the OH from the reaction and the HCl created in the E–V energy transfer process have strongly inverted vibrational distributions. The cross section of the former is found to be about 20 times larger than that of the latter. Although spin forbidden, the E–V process is fast, due to the fact that the 1A″ and 3A″ surfaces of the HOCl intermediate are nearly energetically degenerate over a large region of configuration space. The results suggest that the dynamics of the interaction are dominated by the relatively slow O–Cl collision. The rapid motion of the H atom, in response to changes in the potential created by the motion of the heavier atoms, permits the system to sample the singlet–triplet intersection many times during the collision. OH rotational deactivation is very fast in this system; the average probability for rotational energy transfer in the v'=3 level is more than four times larger than the gas kinetic collision probability. The time evolution of both vibrational distributions is also reported, and fast V–V energy transfer from vibrationally excited OH to ground state HCl is observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.454124
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  • 5
    Digitale Medien
    Digitale Medien
    The dynamics and microscopic kinetics of the reactions of O(1D2) atoms with CHCl3 and CHF3 (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 203-209 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The energy disposal and branching ratios in the reactions of O(1D2) with CHCl3 and CHF3 have been measured using an implementation of time-resolved Fourier transform spectroscopy in this laboratory. The infrared emission from the products of the reactions is measured as a function of time after the creation of the O(1D2) atom by UV photolysis of ozone. The reaction with CHCl3 produces OH, HCl, and CO as primary products. The OH vibrational excitation indicates simple abstraction dynamics. The HCl has much lower vibrational excitation, characteristic of a longer-lived insertion-elimination process, which also produces CO in the decomposition of the internally excited Cl2CO product. Only HF is observed in the reaction with CHF3. In this case the vibrational distribution is nonmonotonic, indicating contributions from two microscopic channels, possibly associated with the formation of F2CO in both the ground (X˜ 1A1) and first excited (A˜ 1A2) states.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.453616
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  • 6
    Digitale Medien
    Digitale Medien
    The initial product vibrational energy distribution in the reaction between O(1D2) and H2 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 1412-1417 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We report the first determination of the initial vibrational distribution in the OH product of the reaction between O(1D2) and H2. The measurement was made using a novel time-resolved Fourier transform spectroscopic technique which permits the observation of spectra on a microsecond time scale at a known time after the initiation of a reaction. The result is P(v'=1:2:3:4)=0.29:0.32:0.25:0.13 suggesting that the reaction dynamics involve very large attractive energy release during reagent approach followed by an extremely short-lived interaction leading to products within a few vibrational periods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.451230
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  • 7
    Digitale Medien
    Digitale Medien
    Energy partitioning in O(1D2) reactions. II. O(1D2)+CH4 → OH(v')+CH3 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 745-749 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The complete OH vibrational distribution created by the reaction of O(1D2) with CH4 has been recorded directly, using low pressure infrared emission spectroscopy. The result shows that the energy is partitioned nonstatistically into this degree of freedom. The population of OH(v'=2) is approximately equal to or slightly greater than that of OH(v'=1) under the conditions of this experiment and substantial populations are recorded from all levels up to OH(v'=4), the maximum allowed by the exoergicity of the reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.450571
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  • 8
    Digitale Medien
    Digitale Medien
    Energy distributions in the HF and CO products of the reaction of F atoms with HCO (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 1873-1882 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The initial energy distributions in both products of the title reaction have been measured using a variant of the low-pressure infrared chemiluminescence technique. The vibrational populations of both products decrease with increasing vibrational level, indicating of the formation of a long-lived HFCO intermediate. The HF vibrational population is well represented by a (restricted phase space) statistical calculation. The CO vibrational excitation is considerably colder than this calculation predicts. These results, combined with ab initio reaction coordinate calculations suggest that free exchange of energy among the modes of the HFCO intermediate ceases early in the exit channel. Thereafter, an excess of energy is partitioned into relative translation of the products.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.448371
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  • 9
    Digitale Medien
    Digitale Medien
    Energy partitioning in atom–radical reactions: The reaction of F atoms with NH2 (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 4524-4536 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: An extension of the low-pressure infrared chemiluminescence technique has allowed the measurement of energy partitioning in the atom/radical reactions: F+NH2→HF+NH, F+ND2→DF+ND. A complete numerical model of the experiment is described in detail including its parametrization. This model allows the unambiguous determination of the primary energy distribution of the above reactions. These reactions give inverted product energy distributions, in contrast to the isoelectronic F+OH→HF+O reaction. The inverted primary energy distribution for F+NH2/ND2 indicates a direct abstraction mechanism. Ab initio quantum chemical computations on some features of the relevant potential energy surfaces support this direct abstraction route. An energetically accessible transition state, having approximately zero barrier, is found on the triplet surface which directly correlates reagents and products. The geometry of this triplet transition state is also suggestive of strong HF vibrational excitation. Abstraction on the triplet surface provides an alternative pathway to reaction on the lowest singlet surface, which contains a deep potential energy well corresponding to NH2F.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.448707
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  • 10
    Digitale Medien
    Digitale Medien
    Assessment of oesophagitis by histology and morphometry (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Histopathology 14 (1989), S. 0 
    Details
    ISSN: 1365-2559
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Morphometric measurements of nuclear area, nuclear concentration and nucleolar dimensions in defined tissue zones of orientated oesophageal biopsy sections were compared between three patient groups–asymptomatic/normal endoscopy (n= 8): symptomatic reflux/normal endoscopy (n= 17); and symptomatic/endoscopic oesophagitis (n= 15). No significant differences could be shown for any mean parameter between clinical groups. In a further group of 16 patients, identical morphometric measurements were made in non-orientated grasp biopsies and correlated with prolonged ambulatory pH data. No significant correlations could be shown between nuclear parameters and acid reflux measurements. These results suggest that morphometric measurement cannot be recommended as a diagnostic tool in the diagnosis of oesophagitis, although it may be useful in the assessment of individual therapeutic response in clinical trials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2559.1989.tb02166.x
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