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Effect of Pulse Energy on the Optical Properties of ZnS Thin Films Prepared Using Pulse Laser Technique
Khalid Mohammed Haroun,
Mohammed Nouman Mohammed Abdalla,
Sohad Saad Elwakeel,
Yousif Hassan Alsheikh Abd Alraheim
Issue:
Volume 7, Issue 5, September 2018
Pages:
173-179
Received:
6 October 2018
Accepted:
22 October 2018
Published:
19 November 2018
Abstract: In these work four samples of ZnS thin films deposited on glass substrate using pulse laser deposition method with different pulse energies, the effect of the laser pulse energy on the optical properties of the four ZnS thin films fabricated was studied. Q-Switched Nd: YAG laser with the fundamental wavelength 1064 nm, laser Pulse energies of (125, 150, 175, and 200) mj with fixed number of pulses of 20, and pulse repetition rate of 5 Hz were used. The target to the substrate distance and angle were kept fixed. The film thicknesses were measured using FESEM measurement tool. The thickness of the deposited ZnS thin films was found to be linearly dependent on the pulse energy used. The transmission spectra in the tested region (532 to 915) nm were found to be in the range from 0.41 to 0.59% depending on the ZnS thin film thickness, and for each ZnS thin film the transmission spectrum is unique. The refractive indices of all samples were determined; and for each sample and it were found to change with wavelength, the highest refractive index of 5.6 at 915 nm was obtained for the sample of the smallest thickness 0.49 microns. Transmission spectra, absorption coefficients and the refractive indices they were in good agreement with the literature.
Abstract: In these work four samples of ZnS thin films deposited on glass substrate using pulse laser deposition method with different pulse energies, the effect of the laser pulse energy on the optical properties of the four ZnS thin films fabricated was studied. Q-Switched Nd: YAG laser with the fundamental wavelength 1064 nm, laser Pulse energies of (125,...
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Quantum Zeno Effect and Atomic Population Inversion
Jiu-Ming Li,
Bo-Ying Zhang,
Xue-Qun Yan
Issue:
Volume 7, Issue 5, September 2018
Pages:
180-184
Received:
1 October 2018
Accepted:
25 October 2018
Published:
26 November 2018
Abstract: Quantum Zeno effect can be applied to quantum information processing，and can reveal the nature of quantum measurement. In addition, it has also many potential applications. This suggests that studying the quantum Zeno effect has great theoretical and experimental significance. In this work, the system of a two-level atom interacting with a single mode field is considered and the dynamics of the system subjected to successive projection measurements is studied, and the quantum Zeno effect is presented. Moreover, the influence of the quantum Zeno effect on atomic population inversion is discussed. Based on Schrödinger equation, the survival probability of the initial state of the two-level atom subjected to frequently repeated measurements can be obtained. The survival probability depends on the time interval between measurements. It is seen that the exponential decay of the system under slowly frequent measurements is presented instead of the naturally oscillatory process. For slowly repeated measurements the atomic population inversion and the survival probability of initial state decline rapidly at the early time and then both of them become unchanged. As the time intervals of the measurements are sufficiently short, the quantum Zeno effect occurs. These results have also shown how the measurement can inhibit the atomic population inversion.
Abstract: Quantum Zeno effect can be applied to quantum information processing，and can reveal the nature of quantum measurement. In addition, it has also many potential applications. This suggests that studying the quantum Zeno effect has great theoretical and experimental significance. In this work, the system of a two-level atom interacting with a single m...
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Kinetic Modelling of Atmospheric Pressure Nitrogen Plasma
Md. Ziaur Rahman,
Mohammed Mynuddin
Issue:
Volume 7, Issue 5, September 2018
Pages:
185-193
Received:
10 November 2016
Accepted:
24 March 2017
Published:
5 December 2018
Abstract: This model describes the production and destruction mechanism of nitrogen plasma at atmospheric pressure. We have studied the mechanisms of chemical dissociation, ionization, ion conversion and recombination in nitrogen plasmas, with kinetic temperature (Tg) of the free electrons being higher than the kinetic temperature (Tg) of heavy species. Therefore, the investigation of nitrogen plasma species in a wide range of pressure from 1 Torr to 760 Torr is interesting phenomena for obtaining the equilibrium state when the nitrogen species breakdown. In order to calculate the species densities to reach thermodynamic equilibrium under various conditions, a set of chemical kinetic reactions of nitrogen under consideration have been simulated. It solves the particle balance equations for a set of interacting species. In this study 16 reactions and 4 species of Nitrogen N, N2, N+, N2+ and electron have been considered. The densities of the charged and neutral species are modeled by continuity equations which includes the relevant plasma-chemical kinetics. Nitrogen species density is guided by continuity equation where chemical processes and Arrhenius form are used to follow the change of species density over the time. To calculate the species densities over pressure, temperature and time the continuity equations of the 16 reactions for the 5 species under consideration giving their initial pressure, densities and temperatures, with the latter held constant have been solved. The variations of species densities have been investigated as a function of pressure ranging from 1 to 760 Torr. This model shows that as the pressure is increased the species densities of nitrogen plasma also increase from pressure 1 to 200 Torr and after pressure above 200 Torr the species densities become almost saturated. The change of species densities at various temperatures ranging from 2000 Kelvin to 25000 Kelvin is successfully investigated. The destruction and production rates of the nitrogen species also have been calculated within the time ranging from 0 to 19nS and it shows that the density of nitrogen plasma increases with time. In our study we have considered the gas and electron temperature as 10k Kelvin and 4eV respectively.
Abstract: This model describes the production and destruction mechanism of nitrogen plasma at atmospheric pressure. We have studied the mechanisms of chemical dissociation, ionization, ion conversion and recombination in nitrogen plasmas, with kinetic temperature (Tg) of the free electrons being higher than the kinetic temperature (Tg) of heavy species. Ther...
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