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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 512-518 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Cluster ion distributions of water in a molecular beam are investigated by femtosecond ionization at 780 nm and reflectron time-of-flight mass spectrometry. The electric field strength generated by the ultrashort laser pulses is sufficient to efficiently ionize most of the molecules that are present in the molecular beam. In this work ion signals of large water clusters containing up to 60 monomers are reported. Upon ionization rapid proton transfer is observed, leading to the formation of protonated water cluster ions. Unprotonated clusters (H2O)n+(n〉2) are not observed in the mass spectra. The configurational energy imparted to the protonated clusters induces unimolecular dissociation on the μs time scale. These metastable reactions are characterized by modeling the ion trajectories in the mass spectrometer. The numerical procedure in conjunction with the integrated parent and daughter intensities results in unimolecular dissociation rates as a function of cluster size. Additional information about proton transfer reactions is obtained by the investigation of deuterium substitutions. Even though these substitutions correspond to large relative changes in the mass of the atom as well as in the zero point energy, unprotonated (D2O)n+ clusters of significant abundance are not produced in supersonic expansions of deuterated water. An additional result of this work is the observation of doubly charged ions above a critical cluster size (n=37). © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Optics Communications 80 (1990), S. 31-36 
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Optics Communications 95 (1993), S. 46-50 
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 64 (1996), S. 109-113 
    ISSN: 1432-0630
    Keywords: PACS82.40; 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Direct conversion of solar radiation into useful, storable and transportable chemical products is the primary goal of solar chemistry. In this paper we discuss some fundamental aspects of photochemistry at elevated temperatures. We show that luminescence can serve as an indicator of the potential use of a system as a photoconverter. As an example we present experimental data on the chemical potential and on the lifetime of the excited states of ZnO. The low luminescence quantum yield together with a lifetime of about 200 ps indicate that an efficient photochemical conversion on ZnO is highly improbable. We believe this to be a general feature of chemical systems based on a semiconductor photocatalyst, in particular of photoreactions at a solid/gas interface.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 38 (1987), S. 147-150 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 37 (1986), S. 150-154 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0649
    Keywords: PACS: 42.65.Dr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 2 , N2, and CO2. For CO2 additional experiments have been performed at reduced pressure and in a molecular beam. By delaying the probe pulse a periodic recovery of the DFWM signal is observed. The period of these transients can be assigned unambiguously to rotational Raman transitions of the ground state within the laser bandwidth. The decay of the transients yields the collisional dephasing of the Raman-induced polarization. At zero delay also optical-field-induced birefringence of electronic nature contributes to the signal. The different time scales of the Raman and electronic effects allow us to estimate their relative strength.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Sozial- und Präventivmedizin 22 (1977), S. 230-234 
    ISSN: 1420-911X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary As well in scientific spheres as in public opinion, the idea of mass media predominant power is still persistent: they are supposed to be able to influence opinion, which is understood as a homogeneous conglomerate of persons being individually submitted to their action, according to a single stimulus-answer type diagram. Mass media sociology has been at the beginning widely accountable for this conception. Lately this too simple image, inferring from the concept of mass media the existence of a mass public, has been abandoned. Whatever information may be transmitted, it is not received in the same way by all persons. Everyone selects the various media he uses, «reads», keeps in mind or rejects information according to his socio-cultural characteristics, his ideological choices, his linguistic and cultural decoding abilities. Moreover, it is far from being granted that after having overstepped these diverse filters, information will produce an effect in such a sense desired by the communicator. It happens that the effect can be opposite (a bommerang reaction, as it brought to light during a famous radioscopy medical propaganda which turned out to increase suspicion among the public, may be possible). However, in a general way, unimportant or long-term effects (sleeper effect) are noticed in the mass media field. Their contribution is rather to reinforce the occurring cultural changes and opinions than to modify them. Most of all, mass media could not do without an indispensable relay: the structure of social relations in which everyone is placed, specifying the kind of information he may receive, accept or neglect. The part played by the opinion leaders is in this concern as important as the one played by mass media themselves. No work on information can be grounded on a sole media propaganda recourse. It should be based on a knowledge of the concerned population structure and on socio-cultural characteristics of its diverse strata.
    Notes: Résumé Tant dans les milieux scientifiques que dans l'opinion publique persiste l'idée de la toute-puissance des mass media: ils sont supposés pouvoir influencer l'opinion, conçue comme une masse homogène d'individus soumis individuellement à leur action, selon un schéma univoque de type stimulus-réponse. Largement responsable, à ses débuts, de cette conception, la sociologie des mass media a, par la suite, détruit cette image simpliste qui déduit faussement de l'existence des moyens de communication de masse celle d'un public de masse. Quelle que soit l'information transmise, celle-ci n'est pas reçue de la même manière par tous les individus. Chacun sélectionne les divers media qu'il utilise, «lit», retient ou rejette l'information en fonction de ses caractéristiques socio-culturelles, de ses options idéologiques, de ses capacités linguistiques et culturelles de déchiffrement. De plus, il est loin d'être prouvé qu'après avoir franchi ces divers filtres, l'information produise un effet dans le sens voulu par l'émetteur: l'effet peut parfois être inverse (effet boomerang, mis en évidence lors d'une campagne de propagande pour la radioscopie qui augmenta la méfiance à son égard). D'une manière générale, les effets des mass media sont faibles, ne jouent qu'à long terme (sleeper effect) et contribuent plus au renforcement des mutations culturelles en cours, des opinions, qu'à leur changement. Surtout, les mass media ne sauraient se passer du relais indispensable de cet autre médiateur qu'est la structure des relations sociales dans laquelle chaque individu est situé et qui détermine spécifiquement le type d'information qu'il reçoit, accepte ou néglige. A ce niveau, le rôle des leaders d'opinion est aussi important que celui des mass media eux-mêmes. Aucune action d'information ne peut se baser sur un recours exclusif à la propagande par les media. Elle doit s'appuyer sur une connaissance approfondie de la structure de la population concernée et des caractéristiques socio-culturelles de ses diverses strates.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Sozial- und Präventivmedizin 22 (1977), S. 312-312 
    ISSN: 1420-911X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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