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  • 1
    Digitale Medien
    Digitale Medien
    Photochemical pathways of water on palladium (111) at 6.4 eV (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 8393-8402 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100174a065
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  • 2
    Digitale Medien
    Digitale Medien
    Photoinduced pathways to dissociation and desorption of dioxygen on silver (110) and platinum (111) (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 1759-1768 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100157a051
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  • 3
    Digitale Medien
    Digitale Medien
    Laser-induced interaction of ammonia with GaAs(100). II. Desorption dynamics (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 5868-5875 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: UV laser irradiation of ammonia adsorbed on GaAs(100) leads to molecular desorption, with a mean translational temperature of 〈Etrans/2k(approximately-greater-than)=300 K, independent of photon energy and isotope substitution. However, the photodesorption cross section depends strongly on isotope substitution: σNH3/σND3=4.1 at hν=6.4 eV. This isotope effect is too large to be accounted for by the mass difference in the leaving particles (NH3 vs ND3), but can be successfully explained in terms of an isotope effect in the internal N–H(D) coordinates. We take this as evidence for uv-driven photodesorption from electronically quenched, but vibrationally hot ground state ammonia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.463746
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  • 4
    Digitale Medien
    Digitale Medien
    Laser-induced interaction of ammonia with GaAs(100). I. Dissociation and nitridation (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 5856-5867 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: UV laser irradiation of ammonia adsorbed on GaAs(100) leads to molecular desorption and dissociation. A nitride passivation layer can be formed on the GaAs surface at 100 K by simultaneous exposure to ammonia and uv photons in a UHV environment. The nitride layer consists of a mixture of Ga and As nitrides. While the dominating GaN surface species is thermally stable, AsN desorbs below 800 K. Surface NH2 is identified as an intermediate. The implication of this study for selective area passivation and GaN growth is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.463745
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  • 5
    Digitale Medien
    Digitale Medien
    Surface plasmon enhanced photochemistry: Mo(CO)6–Al–quartz (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 7015-7016 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We demonstrate that surface plasmon oscillations excited at an adsorbate covered metal–vacuum interface can effectively couple to the electronic system of the adsorbed molecule. Using p-polarized light (hν=3.5 eV) incident at the surface plasmon resonant angle in Kretschmann's attenuated-total-reflection (ATR) configuration, we observe a strong enhancement of the photodissociation rate of Mo(CO)6 from a 180 A(ring) Al film, evaporated on a quartz prism in UHV.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.463211
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  • 6
    Digitale Medien
    Digitale Medien
    The role of direct and substrate excitation in ultraviolet photolysis of phosgene on Pt(111) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1555-1563 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The photodissociation rate of phosgene (Cl2CO) adsorbed on Pt(111) has been measured as a function of photon energy at normal incidence and as a function of incident angle using p-polarized light. Compared to the gas phase, the wavelength dependence of the initial photolysis cross section on the surface is redshifted. The angular response to p-polarized light is wavelength dependent. Above 315 nm, the angular dependence correlates with calculated metal absorption. At 280 nm, the angular dependence is much too strong to be accounted for solely by substrate excitation. A combination of substrate and direct excitation is adequate. This is the first direct evidence, for monolayers on metals, that both direct and substrate excitation contribute to surface photochemistry but dominate at different wavelengths.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.460013
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  • 7
    Digitale Medien
    Digitale Medien
    Surface photochemistry 15: On the role of substrate excitation (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2681-2682 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The rates of photodissociation and photodesorption of dioxygen adsorbed on Ag (110) under ultraviolet irradiation have been measured as a function of polarization at normal incidence. No dependence of the rate was found on the angle between the O2 bond axis and the electric vector of the incident light. This result supports a mechanism for surface photochemistry in which substrate excitation is the dominant process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457964
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  • 8
    Digitale Medien
    Digitale Medien
    Photochemical decomposition of AsH3 on GaAs(100) (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 605-615 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Molecular AsH3, adsorbed on Ga-rich GaAs(100) at 115 K, dissociates readily upon uv irradiation with 193, 248, and 351 nm excimer laser light. In the initial photodissociation step one As–H bond cleaves, leaving all the AsH2, and a large fraction of the H, adsorbed to As. The AsH2 further photodissociates to give As–H and Ga–H. The final steps, photochemical removal of hydrogen from Ga–H and As–H, lead to As deposition. The photodissociation cross section decreases sharply with the extent of photolysis. The wavelength dependence, compared to the gas-phase absorption cross section, extends to much lower photon energies and indicates that substrate-mediated excitation dominates the observed chemistry. There are strong isotope effects in all the cross sections; these are related to mass-dependent substrate-mediated quenching of the excited states. Implications for photon-assisted organometallic chemical vapor deposition are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.463556
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  • 9
    Digitale Medien
    Digitale Medien
    Surface photochemistry. II. Wavelength dependences of photoinduced dissociation, desorption, and rearrangement of O2 on Pt(111) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5011-5020 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A Pt(111) surface saturated with molecular oxygen was irradiated by UV light from a mercury arc lamp with various cutoff filters. High-resolution electron energy-loss spectroscopy (HREELS) and temperature programmed desorption mass spectroscopy (TPD) were used to characterize the products retained on the surface. Upon UV irradiation at 95 K, chemisorbed O2 (peroxo) undergoes dissociation, desorption and rearrangement. Different wavelength dependences were observed for the three processes: dissociation was not observed at wavelengths longer than 295 nm, in agreement with gas phase photodissociation of the O–O bond in hydrogen peroxide; desorption and rearrangement became negligible at wavelengths longer than 420 nm, in agreement with the photolysis of an organometallic peroxoplatinum complex. For wavelengths between 230 and 315 nm, the average cross sections of dissociation and desorption were estimated to be 5.7×10−20 and 1.2×10−19 cm2 , respectively. The possible origins of the three processes are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.456741
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  • 10
    Digitale Medien
    Digitale Medien
    Direct and precursor dynamics in dissociative hydrogen chemisorption on Ni(100) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7442-7447 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We report evidence for the coexistence of direct and precursor dynamics in the dissociative chemisorption of H2 on Ni(l00). Hydrogen and deuterium uptakes on Ni(l00) were measured at various surface temperatures by following the secondary ion ratios, Ni2 H+/Ni+ and Ni2 D+/Ni+ , which are proportional to surface hydrogen and deuterium coverage on both clean and carbon-covered Ni(100). Between 100 and 200 K on clean Ni(l00), the initial sticking coefficient of hydrogen decreases, but only slightly, as the surface temperature increases. The decrease is more pronounced both in the presence of predosed carbon and for deuterium adsorption on Ni(100). This is interpreted as due to the involvement at low temperatures of a molecular precursor which mediates dissociative adsorption at low temperatures. The precursor probably involves surface defects and sites formed in the presence of carbon. In addition to the precursor channel, a direct dissociation channel also operates, and dominates for T≥200 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.456224
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