ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Ultraviolet photoemission study of oligothiophenes: π-band evolution and geometries (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4077-4092 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ultraviolet photoelectron spectroscopy (UPS) has been applied to the investigation of the electronic structure of oligothiophenes with 4–8 thiophene rings. In a series of α-linked oligomers (αn with n being the number of rings), a systematic evolution of the π band is observed. Several peaks which correspond to the π band are observed in the region of 0.7–3 eV below the Fermi level (EF), and the bandwidth becomes broader with increasing n. The nonbonding π band is observed at 3.5 eV below EF and its energy is almost independent of the number of thiophene units. UPS spectra of α7 and α8 are fairly similar to the spectra of polythiophene, showing that these oligomers are good model compounds of the polymer. The ionization threshold energy of α7 and polythiophene was observed to be 5.3 eV. The effect of irregularity on the π-electron system was also studied by using oligomers which contain a β linkage or a vinylene group at the middle of the molecule. The UPS spectra showed that the β linkages significantly affect the electronic structure of polythiophene, while the vinylene group does not. In order to analyze the UPS spectra and to investigate the electronic structures of oligomers, the orbital energies and the geometries of these oligomers are calculated by the semiempirical MNDO-SCF-MO (modified neglect of diatomic overlap self-consistent-field molecular orbital) method. Theoretically simulated spectra of these oligothiophenes derived from the obtained orbital energies by Gaussian broadening are compared with the observed ones. The agreement between the observed and calculated spectra is very good, particularly in the π region. It is shown from the optimized geometry that (1) αn 's have planar structure and π electrons are delocalized, (2) the oligomer with β linkages has nonplanar structure leading to limited delocalization of π electrons, and (3) the oligomers with a vinylene group are almost planar and the disturbance by the vinylene group on the delocalization is small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458561
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Cycloaddition chemistry of thiophene on the silicon (111)-7×7 surface (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 3287-3296 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The mechanism of the cycloaddition reaction between thiophene and Si(111)-7×7 has been investigated using thermal desorption spectroscopy (TDS), high resolution electron energy loss spectroscopy (HREELS), electronic electron energy loss spectroscopy (EELS), scanning tunneling microscopy (STM), and PM3 semiempirical calculations. The results show that thiophene binds on Si(111)-7×7 through a [4+2] cycloaddition reaction between the 2, 5 C-atoms of thiophene and the adjacent adatom-rest atom pairs on Si(111)-7×7. Semiempirical PM3 calculations based on the cluster model further confirm this di-σ bonding configuration. A stepwise surface diradical mechanism has been proposed to account for the regioselective [4+2] cycloaddition reaction. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1386435
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Efficient pseudospectral methods for density functional calculations (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 10131-10141 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Novel improvements of the pseudospectral method for assembling the Coulomb operator are discussed. These improvements consist of a fast atom centered multipole method and a variation of the Head–Gordan J-engine analytic integral evaluation. The details of the methodology are discussed and performance evaluations presented for larger molecules within the context of DFT energy and gradient calculations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481704
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Recombination of N+4 ions with electrons (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7356-7359 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Spectroscopic observations of N2 second positive band emissions from photoionized afterglow plasmas indicate that dissociative recombination of electrons with N+4 ions results in the formation of N2 molecules in the C 3Πu (v=0,1) state. The measured recombination rate coefficient of (2.6±0.3)×10−6 cm3/s at T=300 K is considerably larger than that found in earlier work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461361
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Neutral-stabilized electron–ion recombination in ambient helium gas (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 5443-5446 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured rates of recombination of electrons with simple molecular ions in the presence of helium at densities from 2.5×1019 to 2.9×1020 cm−3 at reduced temperatures of 77, 125, and 150 K. The results agree surprisingly well with the neutral, collisional recombination mechanism proposed by Bates and Khare for atomic ions recombining in plasmas of high neutral density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460505
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Annealing temperature and O2 partial pressure dependence of Tc in HgBa2CuO4+δ : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7127-7129 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Samples of HgBa2CuO4+δ (Hg-1201) were annealed under various conditions. After carefully controlling annealing time, annealing temperature (Ta), and O2 partial pressure (P0), we were able to find the reversible annealing conditions for Hg-1201. Under 1 atm O2 at 260 °C≤Ta≤400 °C, the obtained Tc is nearly the same (∼97 K). However, it decreases quickly with Ta(approximately-greater-than)300 °C in high vacuum (P0∼10−8 atm), and reaches zero at Ta=400 °C. On the other hand, Tc decreases with the decrease of Ta in high-pressure O2 (∼500 atm) and reaches ∼20 K at about 240 °C. In the entire annealing region, the oxygen surplus varies significantly from 0.03 to 0.4, and a wide range of Tc variation (0→97 K→20 K) was obtained with anion doping alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358052
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Absorption spectroscopy of nonlinear excitations in polyaniline (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 2664-2669 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present near steady state photoinduced absorption spectra of two forms of polyaniline. Both the emeraldine base (nondegenerate ground state) and pernigraniline (degenerate ground state) exhibit long lived photoinduced nonlinear excitations with transient absorptions within the π→π* gap. In the case of the emeraldine base, two well-resolved photoinduced absorption bands are observed with maxima at 0.9 and 1.47 eV, accompanied by a bleaching of the 2 eV absorption edge. The different relaxation rates of the two bands indicate that they arise from two independent photoinduced nonlinear excitations. The results are discussed in terms of intrachain and interchain excitations. The possibility of deep traps on defect sites in pernigraniline is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464147
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    ECR ion sources at the Institute of Modern Physics: From classical to fully superconducting device : Papers from the Ninth International Conference on Ion Sources (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 525-527 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electron cyclotron resonance (ECR) ion sources are used for cyclotron complex and atomic physics research at the Institute of Modern Physics (IMP). Intense beams of highly charged gaseous and metallic ions could be produced by the IMP 14.5 GHz ECR ion source (LECR2-Lanzhou Electron Cyclotron Resonance Ion Source No. 2). A particular emphasis has been put on the production of metallic ion beams recently. Metallic ion beams of Mg, Ca, Fe, Ni, Cu, Zn, and Pb were tested at the IMP 14.5 GHz ECR ion source (LECR2) to improve beam intensities and long-term stability. A new ECR ion source (Lanzhou Electron Cyclotron Resonance Ion Source No. 3), an upgraded version of the IMP 14.5 GHz ECR (LECR2) but with double-frequency wave heating (10 GHz+14.5 GHz), is under commissioning. The preliminary results of this new source will be presented. To satisfy the requirements of the heavy ion cooling storage ring that is under construction at IMP, a fully superconducting ECR ion source (Lanzhou Electron Cyclotron Resonance Ion Source with Superconducting Coils) with a completely new structure is being developed for the production of intense heavy ion beams of very high charge states, such as Xe30+ and U40+. The superconducting magnet consists of three axial solenoid coils and six saddle-curved sextupole coils with a cold iron structure as field booster and clamp. At full excitation, this magnet assembly will produce maximum peak fields on axis of 4.0 T at the injection, 2.2 T at the extraction region, and a radial sextupole field of 2.0 T at plasma chamber wall. The design features and status of this new superconducting ECR ion source will be presented. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429319
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Lifetime and degradation effects in polymer light-emitting diodes (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 2441-2447 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The operational lifetime of polymer light-emitting diodes was studied at several temperatures in the range from 25 to 85 °C. When operated in constant current mode, at luminances greater than 100 cd/m 2, lifetimes of around 20 000 h were noted. Two significant changes in performance were found during continuous operation: the luminance of the devices varied in a nonmonotonic fashion, and the operating voltage increased in a linear fashion. Both of these changes were thermally activated, with the changes accelerated at higher temperatures. These changes are also accelerated at higher current densities. We discuss possible mechanisms for these degradation processes. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369564
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    A new ECR ion source for atomic physics research at Institute of Modern Physics : Papers from the Ninth International Conference on Ion Sources (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 580-581 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new electron cyclotron resonance (ECR) ion source (LECR3—Lanzhou Electron Cyclotron Resonance Ion Source No. 3) has been constructed this year. The main purpose of this source is to provide highly charged ion beams for atomic physics and surface physics research. The design of this ion source is based on the IMP 14.5 GHz ECR ion source (LECR2—Lanzhou Electron Cyclotron Resonance Ion Source No. 2) with double rf heating by inserting waveguide directly and aluminum chamber. Furthermore, the volume of the plasma chamber is larger than that of LECR2 so as to increase the rf power and improve beam intensity for highly charged ions. But the hexapole field on the chamber wall is kept the same value in order to compare with the performance of LECR2. After only four days conditioning the first test results were obtained. The final result of this ion source is expected to be better than LECR2's. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429317
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...