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  • 1
    Electronic Resource
    Electronic Resource
    Electron degradation and yields of initial products. IV. Subexcitation electrons in molecular oxygen (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3081-3086 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electron slowing-down processes in molecular oxygen gas in the subexcitation domain (below the ionization threshold) are studied by using the Spencer–Fano (SF) equation and its simplification, the continuous-slowing-down approximation (CSDA), both in time-dependent and time-independent representations. Compared to the previously studied cases of N2 and CO2, O2 has the special features in its inelastic cross sections of (i) strong delta-function-like peaks in the vibrational excitation cross section below 1.3 eV and (ii) very low energy thresholds of electronic excitation channels. These features provide a stringent test for the CSDA. Indeed, our results clearly show for the first time that the CSDA fails even qualitatively to reproduce the electron degradation spectrum given by the exact SF method over the whole energy regime studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456652
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  • 2
    Electronic Resource
    Electronic Resource
    Chemical reaction in medium density fluid. Solvent density effects on the dimerization equilibrium of 2-methyl-2-nitrosopropane in carbon dioxide (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5679-5686 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dimerization equilibrium of 2-methyl-2-nitrosopropane in carbon dioxide was studied in a wide range of solvent density from 200 to 1100 kg m−3 at 25.0 and 35.0 °C. We found an inversion of the density dependence of the equilibrium constant. The configurational volume change for the dimerization has a large positive value in the medium density region, although it is negative in the high density region as usually observed for the bond formation reactions in the liquid state. This anomaly is reproduced by the cavity distribution function calculated from the integral equation based on the HNC or PY approximation for the Lennard-Jones fluid model. The large positive value in the medium density region is interpreted in terms of desolvation effect due to the dimerization. The long-range correlation between molecules due to attractive forces is suggested to play an important role in determining the reaction volume in the medium density region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456423
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  • 3
    Electronic Resource
    Electronic Resource
    Electron degradation and yields on initial products. II. Subexcitation electrons in molecular nitrogen (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 7229-7237 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Subexcitation electrons lose their kinetic energy through vibrational excitation, rotational excitation, and elastic collisions in molecular gases. Initial yields of vibrationally and rotationally excited states of nitrogen molecules are calculated by using the Spencer–Fano equation (SFE) and its simplification, the continuous-slowing-down approximation (CSDA), both in time-independent and time-dependent representations. One focus of the present study is a close comparison of the CSDA with the rigorous treatment of the SFE in the subexcitation domain. The present result reveals for the first time distinct energy regions in which either vibrational excitation or rotational excitation dominates. This recognition explains the different time dependence of the yields of vibrational and rotational excitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455302
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  • 4
    Electronic Resource
    Electronic Resource
    Electron degradation and yields of initial products. III. Dissociative attachment in carbon dioxide (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6220-6225 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We demonstrate the importance of subexcitation electrons in CO2 (with energies below 6 eV) by studying the yield of negative-ion formation in the dissociative attachment process e−+CO2→CO+O−. We evaluate the electron degradation spectrum and the time dependence of the degradation process within the continuous-slowing-down approximation. Slowing down by vibrational and other excitation collisions and the O− production are competing processes. This explains why the O− yield is larger for subexcitation electrons with energies above 3.8 eV, which avoid the large energy loss by electronic excitation and can still pass through the resonance at about 4 eV. The attachment at 8 eV with a much larger resonance-like cross section contributes only about 30% to the total O− yield in the degradation process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455728
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical equilibrium in argon: Anomaly of density dependence of dimerization reaction in the medium density region (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2758-2759 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We studied the dimerization equilibrium of 2-methyl-2-nitrosopropane in argon at 25.0 °C from about 500 to 1200 kg m−3. It is clarified that in the simplest solvent, argon, there exists a definite difference in the density dependence of the equilibrium constant between the high and medium density regions. In the high density region, the equilibrium constant shows a sizable increase with the solvent density as in the liquid phase. Near the critical density, however, the equilibrium constant shows little density dependence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456991
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  • 6
    Electronic Resource
    Electronic Resource
    Hyperpolarizabilities of 4-amino-4'-nitrodiphenyl sulfide and all of its chalcogen analogues (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3427-3429 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The quadratic hyperpolarizability tensor of 4-amino-4'-nitrodiphenyl sulfide has been sampled by measurement of the z component of its vector part, when z is the permanent dipole direction. This was also accomplished for the oxygen, selenium, and tellurium analogues. It was found that large differences in their frequency-doubling efficiency as powdered solids are not reflected in this molecular property. The sulfur, selenium and tellurium ethers have about the same hyperpolarizabilities while that of the oxygen member is somewhat lower.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455851
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  • 7
    Electronic Resource
    Electronic Resource
    Autoionization mechanism of the NO molecule: Calculation of quantum defect and theoretical analysis of multiphoton ionization experiment (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1603-1610 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quantum defects of lλ-Rydberg states (l=s,p,d, λ=σ,π,δ) of NO were calculated by SCF and CI methods at various internuclear distances. Employing the multichannel quantum defect theory (MQDT), the recently observed resonantly enhanced multiphoton ionization (REMPI) photoelectron spectra were analyzed with use of the calculated quantum defects. Analysis was made particularly to the autoionization of vibrationally excited Rydberg states of σ and δ symmetry. It is concluded that the autoionization is dominated by the two-step electronic mechanism in which dissociative superexcited state plays a role of intermediate state. Potential curves and electronic coupling strengths of the relevant dissociative states (B' 2Δ and I 2∑) were estimated from this analysis. This provides us with useful information to investigate various dynamic processes involving these superexcited states. Importance of dissociative superexcited state is emphasized in reference to the various dynamic processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457119
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  • 8
    Electronic Resource
    Electronic Resource
    A dynamical formalism of singular Lagrangian system with higher derivatives (1989)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 30 (1989), S. 1122-1132 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The singular Lagrangian system with higher derivatives is analyzed with the aid of the Ostrogradski transformation and the Dirac formalism. The formulation of canonical theory is developed so that the equivalence between the Lagrange formalism and the Hamilton one is maintained. As a practical example, the acceleration-dependent potentials appearing in the Lagrangian of two-point particles interacting gravitationally are dealt with and the equivalence between the two Hamiltonians that follow from the two Lagrangians which are related by the coordinate transformations is shown. It is also shown, when the constraints are all first class, that a consistent generator of gauge transformation is constructed. Typical examples are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.528331
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  • 9
    Electronic Resource
    Electronic Resource
    Pumping wavelength dependence on gain factor of a 0.98 μm pumped Er3+ fiber amplifier (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2573-2575 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gain characteristics of an Er3+-doped fiber are investigated with different pump wavelengths using a tunable Ti:sapphire laser in the 0.98 μm band. Maximum gain was obtained at a pump wavelength of 0.980 μm and the gain profile can be fully explained in terms of the pump absorption spectrum. The 3 dB gain bandwidth for the pump wavelength was 10–14 nm. A gain coefficient of 2.6 dB/mW was obtained for a 60 ppm Er3+-doped fiber with an absorbed pump power of 9 mW.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101982
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  • 10
    Electronic Resource
    Electronic Resource
    Direct areal density measurement by activation technique for plastic hollow shell implosion experiments (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2072-2074 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fuel areal density ρR measurement of imploded plastic hollow shell targets by use of a neutron activation technique is reported. Silicon was doped as an activatable tracer into a hollow shell of tritium-contained deuterated polymer(CDTSi). This target was imploded by 0.53 μm Nd:glass laser light and the induced radioactivity of 28 Al was measured with a β-γ coincidence counting system. The collection efficiency was calibrated by the use of radioactive tracer 24 Na and was verified by comparing the estimated ρR with that simultaneously measured by a knock-on method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102109
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