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1
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Open-Shell SCF-CI Calculations for Radical Cations of Dihydroxynaphthalenes with C_{2v} and C_{2h} Symmetry

100%
Khan Z.
Acta Physica Polonica A
|
1991
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vol. 80
|
issue 1
29-45
EN
Electronic spectra of radical cations of dihydroxynaphthalenes with C_{2v} and C_{2h} symmetry are calculated using an open-shell SCF method with configuration interaction (CI). The characteristic behaviour of electronic transitions depending on the positions of the hydroxyl substituents is discussed. An interesting aspect of this work is the estimation of the first ionization potentials (IP's) of neutral dihydroxynaphthalenes from the energy of the lowest non-Koopmans state for their radical cations. This method for the prediction of IP's is found to be at least as good as that of the Koopmans' theorem with energy correction due to bond perturbation.
2
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Electronic Spectra of Radical Cations and their Correlation with Photoelectron Spectra. VI. A Reinvestigation of Two-, Three-, and Four-Ring Condensed Aromatics

100%
Khan Z.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 6
937-955
EN
Earlier interpretations of the electronic spectra of two-, three-, and four-ring condensed aromatic hydrocarbon radical cations are reexamined in the light of the UV photoelectron spectroscopic data for their neutral precursors and improved open-shell self-consistent field configuration interaction (SCF-CI) calculations. From the electronic transition energies for some 33 aromatic radical cations obtained from electronic absorption spectra (EAS) and those inferred from photoelectron spectra (PES), the following correlation is found between the two types of spectroscopies: E_{EAS} = (0.23 ± 0.20) + (0.98 ± 0.01)E_{PES}. The slope of this line is very close to unity which shows that the matrix shift on going from the solid phase (electronic spectrum) to the vapour phase (PE spectrum) is almost negligible and that there is no appreciable change in the geometry of the molecules on ionization.
3
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Molecular Orbital Studies on Electronic Spectra of Some Substituted Anthraquinone Cation Radicals

63%
Armed M., Khan Z.
Acta Physica Polonica A
|
1995
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vol. 87
|
issue 6
939-951
EN
Electronic transition energies of radical cations of some hydroxy-substi­tuted anthraquinones are calculated using an open-shell self-consistent field method with limited configuration interaction. The results are analyzed and a correlation diagram is given which provides useful information about the characteristic behaviour of the electronic transitions depending on the po­sitions of the hydroxyl substituents. Also, the first ionization potentials of substituted anthraquinones are calculated using an empirical relation con­necting ionization potentials with the lowest-energy non-Koopmans bands for their radical cations. Such information is particularly useful for systems like substituted anthraquinones for which uv photoelectron spectroscopic data are in scarce.
4
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Study of Glass Transition and Crystallization Behavior in Ga_{15}Se_{85 - x}Pb_x (0 ≤ x ≤ 6) Chalcogenide Glasses

51%
Khan Z., Khan S., Alvi M.
Acta Physica Polonica A
|
2013
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vol. 123
|
issue 1
80-86
EN
There has been a growing interest in the synthesis and characterization of amorphous chalcogenide glasses due to their importance in preparing electronic memories, grating, switching devices and their optical applications as good IR transmitting materials. The study of the glass transformations and crystallization processes in the amorphous systems is interesting not only from the fundamental aspect of establishing the reaction mechanism of crystal nucleation and growth, but also from a technological point of view. The present research work is concentrated on the study of glass transition and crystallization behavior in Ga_{15}Se_{85 - x}Pb_x with x=0, 3, and 6 chalcogenide glasses by differential scanning calorimetry. Their amorphous nature has been verified by X-ray diffraction. The differential scanning calorimetry experiments were performed at different continuous heating rates (5 to 25 K/min). The glass transition temperature (T_{g}) and crystallization temperature (T_{c}) of these glasses has been determined from differential scanning calorimetry thermograms. The dependence of T_{g} and T_{c} on the heating rate (β) has been used for the determination of different crystallization parameters such as the activation energy of crystallization (Δ E_{c}), the activation energy for structural relaxation (Δ E_{t}) and the order parameter (n). The results of crystallization were discussed on the basis of different models such as Kissinger's approach and modification for non-isothermal crystallization in addition to Johnson, Mehl, Ozawa and Avrami.
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