Esam A H M E D Tawfiq (original) (raw)
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Engineering and Technology Journal
In this paper, effects of temperature and concentration on the absorption spectra for Polyvinyl c... more In this paper, effects of temperature and concentration on the absorption spectra for Polyvinyl chloride solutions are studied at wavelengths from 200 to 400 nm and with the range of temperature 20, 30, 40, 50, and 60 degrees (C o). Electronic absorption spectra were examined over the wavelength range 200-400 nm by different concentrations (1x10-3 , 8x10-4 , 6.5x10-4, 5x10-4 and 3x10-4)[M]. The UV spectra shifted slightly towards large wavelength with increasing the temperature. The values of the energy gap of polyvinyl chloride are decreasing as concentration and temperature increased. The data shows that the refractive index of the polymer decreases with increasing the wavelength and temperature. The relationship between the absorption coefficient and photon energy of the PVC solutions are calculated.
The influence of Diethyl phthalate (DEP) on the optical characteristics of polystyrene solutions ... more The influence of Diethyl phthalate (DEP) on the optical characteristics of polystyrene solutions in the range between 200 to 400 nm at solvents of different polarities; chloroform, cyclohexane, dichloromethane, and tetrahydrofuran have been recorded. The experimental results showed that the behavior of the photophysical processes of polymer solutions depends on the nature of its environment. The intensity of the absorption and fluorescence spectra depends on the interactions between solvent-solute molecules. The experimental results indicate that the maximum most absorbance bands occur around 262 nm, which depends on the concentration of the quencher. The results did not determine any change in the positions of the most absorption bands. Fluorescence spectra of the polystyrene were measured in chloroform, cyclohexane, dichloromethane, and tetrahydrofuran diluted solutions at room temperature. Fluorescence emission spectra were characterized by one broad main band centered at 295 nm ...
Journal of Al-Nahrain University Science, 2014
The present work, the plasma is simulated using particle model under the action of CO2 laser by u... more The present work, the plasma is simulated using particle model under the action of CO2 laser by using power density 10 15 W per centemete 2 .The behavior of the plasma is studied in three electron density regions below the critical density. The time history of the total energy, kinetic energy, and the drift energy are studied at 0.9ncr, 0.95ncr, and 0.99ncr. The results indicated that the total energy of the system slightly increases at the first time steps after that time a rapid increase in the energy are observed. The time evolution of the kinetic energy is studied, the results show that the plasma heating increases rapidly due to the acceleration of the plasma particles by the laser light. In this work the time history of the drift energy is plotted at each time step of the run.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2000
The effect of solvents of varying polarity on the absorption and fluorescence emission of the Sch... more The effect of solvents of varying polarity on the absorption and fluorescence emission of the Schiff base, 2-{[3-(1H-benzimidazole-2-yl) phenyl]carbonoimidoyl}phenol, was studied using Lippert-Mataga bulk polarity function, Reichardt's microscopic solvent polarity parameter and Kamlet's multiple linear regression approach. The spectral properties follow Reichardt's microscopic solvent polarity parameter better than Lippert-Mataga bulk polarity parameter, indicating the presence of both general solute-solvent interactions and specific interactions. Catalan's multiple linear regression approach indicates the major role of solvent polarizability/dipolarity influence compared with solvent acidity or basicity. The solvatochromic effect was utilized to calculate the dipole moments of ground and excited states of the Schiff base using different methods. Bathochromic shift in the emission spectrum and the increase in dipole moment in the excited state signifies the intramolecular charge transfer character in the emitting singlet state. Fluorescence quenching by aniline was also studied in 1,4-dioxane and n-butanol, and the results were analyzed using sphere of action static quenching and finite sink approximation models.
Diyala Journal For Pure Science, 2020
In this study, the effects of temperature on the absorption and emission spectra of polyvinyl chl... more In this study, the effects of temperature on the absorption and emission spectra of polyvinyl chloride films were investigated in the presence of diethyl phthalate as a quencher. In this paper, diethyl phthalate (DEP) was used as a quencher at different concentrations to study its effect on the behavior of absorption and emission spectra in the wavelength range from 200 to 350 nm. The films have been treated thermally at 25, 40, 50 and 60 o C. The results showed that the absorption spectrum contains two absorption bands for all samples. The first absorption band appeared in the range of 200 to 220 nm. The maximum absorption band was shifted towards red wavelengths depending on the concentration and temperature. The second absorption band appeared from 260 to 300 nm was weak, broad and unaffected by a concentration while showing a simple response to temperature without displacement in the maximum absorption (λmax.). The changes in absorbance as a function of quencher concentration at room temperature (25 o C) are illustrated.
Engineering and Technology Journal
The particle-in-cell plasma simulation program in two dimensions was developed to display the pro... more The particle-in-cell plasma simulation program in two dimensions was developed to display the properties of silver plasma under the effect of Ruby laser 694.3 nm with different intensities; 1012Wcm-2, 1015 Wcm-2, 1018 Wcm-2, and 1020 Wcm-2. The time evolution and the properties of total energy, kinetic energy, and drift energy of the system were examined in the region near the critical density (ne=0.2ncr). The charged particles respond to the laser pulse after a specified period of interaction time in the form of an increase in the energy of the system. This response depends on the intensity of the laser pulse used in this work. A significant increase was observed in plasma energy due to the efficient transfer of laser energy to plasma particles by the Inverse Bremsstrahlung process. The effectiveness of this process is reduced when the laser intensity is increased. This result is shown especially when using 1020 Wcm-2 laser intensity. The results indicated that the plotting of the ...
Engineering and Technology Journal
In this paper, effects of temperature and concentration on the absorption spectra for Polyvinyl c... more In this paper, effects of temperature and concentration on the absorption spectra for Polyvinyl chloride solutions are studied at wavelengths from 200 to 400 nm and with the range of temperature 20, 30, 40, 50, and 60 degrees (C o). Electronic absorption spectra were examined over the wavelength range 200-400 nm by different concentrations (1x10-3 , 8x10-4 , 6.5x10-4, 5x10-4 and 3x10-4)[M]. The UV spectra shifted slightly towards large wavelength with increasing the temperature. The values of the energy gap of polyvinyl chloride are decreasing as concentration and temperature increased. The data shows that the refractive index of the polymer decreases with increasing the wavelength and temperature. The relationship between the absorption coefficient and photon energy of the PVC solutions are calculated.
The influence of Diethyl phthalate (DEP) on the optical characteristics of polystyrene solutions ... more The influence of Diethyl phthalate (DEP) on the optical characteristics of polystyrene solutions in the range between 200 to 400 nm at solvents of different polarities; chloroform, cyclohexane, dichloromethane, and tetrahydrofuran have been recorded. The experimental results showed that the behavior of the photophysical processes of polymer solutions depends on the nature of its environment. The intensity of the absorption and fluorescence spectra depends on the interactions between solvent-solute molecules. The experimental results indicate that the maximum most absorbance bands occur around 262 nm, which depends on the concentration of the quencher. The results did not determine any change in the positions of the most absorption bands. Fluorescence spectra of the polystyrene were measured in chloroform, cyclohexane, dichloromethane, and tetrahydrofuran diluted solutions at room temperature. Fluorescence emission spectra were characterized by one broad main band centered at 295 nm ...
Journal of Al-Nahrain University Science, 2014
The present work, the plasma is simulated using particle model under the action of CO2 laser by u... more The present work, the plasma is simulated using particle model under the action of CO2 laser by using power density 10 15 W per centemete 2 .The behavior of the plasma is studied in three electron density regions below the critical density. The time history of the total energy, kinetic energy, and the drift energy are studied at 0.9ncr, 0.95ncr, and 0.99ncr. The results indicated that the total energy of the system slightly increases at the first time steps after that time a rapid increase in the energy are observed. The time evolution of the kinetic energy is studied, the results show that the plasma heating increases rapidly due to the acceleration of the plasma particles by the laser light. In this work the time history of the drift energy is plotted at each time step of the run.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2000
The effect of solvents of varying polarity on the absorption and fluorescence emission of the Sch... more The effect of solvents of varying polarity on the absorption and fluorescence emission of the Schiff base, 2-{[3-(1H-benzimidazole-2-yl) phenyl]carbonoimidoyl}phenol, was studied using Lippert-Mataga bulk polarity function, Reichardt's microscopic solvent polarity parameter and Kamlet's multiple linear regression approach. The spectral properties follow Reichardt's microscopic solvent polarity parameter better than Lippert-Mataga bulk polarity parameter, indicating the presence of both general solute-solvent interactions and specific interactions. Catalan's multiple linear regression approach indicates the major role of solvent polarizability/dipolarity influence compared with solvent acidity or basicity. The solvatochromic effect was utilized to calculate the dipole moments of ground and excited states of the Schiff base using different methods. Bathochromic shift in the emission spectrum and the increase in dipole moment in the excited state signifies the intramolecular charge transfer character in the emitting singlet state. Fluorescence quenching by aniline was also studied in 1,4-dioxane and n-butanol, and the results were analyzed using sphere of action static quenching and finite sink approximation models.
Diyala Journal For Pure Science, 2020
In this study, the effects of temperature on the absorption and emission spectra of polyvinyl chl... more In this study, the effects of temperature on the absorption and emission spectra of polyvinyl chloride films were investigated in the presence of diethyl phthalate as a quencher. In this paper, diethyl phthalate (DEP) was used as a quencher at different concentrations to study its effect on the behavior of absorption and emission spectra in the wavelength range from 200 to 350 nm. The films have been treated thermally at 25, 40, 50 and 60 o C. The results showed that the absorption spectrum contains two absorption bands for all samples. The first absorption band appeared in the range of 200 to 220 nm. The maximum absorption band was shifted towards red wavelengths depending on the concentration and temperature. The second absorption band appeared from 260 to 300 nm was weak, broad and unaffected by a concentration while showing a simple response to temperature without displacement in the maximum absorption (λmax.). The changes in absorbance as a function of quencher concentration at room temperature (25 o C) are illustrated.
Engineering and Technology Journal
The particle-in-cell plasma simulation program in two dimensions was developed to display the pro... more The particle-in-cell plasma simulation program in two dimensions was developed to display the properties of silver plasma under the effect of Ruby laser 694.3 nm with different intensities; 1012Wcm-2, 1015 Wcm-2, 1018 Wcm-2, and 1020 Wcm-2. The time evolution and the properties of total energy, kinetic energy, and drift energy of the system were examined in the region near the critical density (ne=0.2ncr). The charged particles respond to the laser pulse after a specified period of interaction time in the form of an increase in the energy of the system. This response depends on the intensity of the laser pulse used in this work. A significant increase was observed in plasma energy due to the efficient transfer of laser energy to plasma particles by the Inverse Bremsstrahlung process. The effectiveness of this process is reduced when the laser intensity is increased. This result is shown especially when using 1020 Wcm-2 laser intensity. The results indicated that the plotting of the ...