Isfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202A model to obtain an optimum erbium desity for gain increasing in EDFAA model to obtain an optimum erbium desity for gain increasing in EDFA1121485FAE. ArziA. HassaniF. E. SerajiJournal Article20200202 In this paper, we suggest a novel model, based on input pump power and wave guidestructure, to calculate the Er-density profile in Erbium doped fiber amplifiers. This optimization is carried out for both SMF and DSF fibers. These optimized profiles have a Gaussian-like shape. Using the SMF optimized Er-density profile, high gain enhancement is obtained in a relatively short length of fibers. On the other hand, the DSF optimized profile shows small changes in the gain, which agrees with the previously report on other method of gain enhancement. This model is applicable to all active waveguides and any other dopant as well . In this paper, we suggest a novel model, based on input pump power and wave guidestructure, to calculate the Er-density profile in Erbium doped fiber amplifiers. This optimization is carried out for both SMF and DSF fibers. These optimized profiles have a Gaussian-like shape. Using the SMF optimized Er-density profile, high gain enhancement is obtained in a relatively short length of fibers. On the other hand, the DSF optimized profile shows small changes in the gain, which agrees with the previously report on other method of gain enhancement. This model is applicable to all active waveguides and any other dopant as well .https://ijpr.iut.ac.ir/article_1485_62503c8e93d19b012368cb9bb2d6ce66.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202Measurement and calculation of high energy neutron flux in aluminium, graphite, water and paraffin assemblyMeasurement and calculation of high energy neutron flux in aluminium, graphite, water and paraffin assembly13211486FAR. Izadi-NajafabadiR. Koohi-FayeghH. AfaridehJournal Article20200202 In the experimental section of this project, the energy spectrum of fast neutrons is measured, after being passed through large blocks, approximately lm3 each, of graphite, aluminium, water and paraffin. Neutrons were produced via 7Li(p,n)7Be reaction by bombarding a Lithium target with 25 or 30 MeV protons of the cyclotron at the Nuclear Research Centre for Agriculture and Medicine in Karaj. Measurements are done using a 76 × 76mm NE-213 scintillator detector, in two points outside the blocks, one in the direction of proton beam and the other normal to it. In analyzing the results of the experiments, SCINFUL and RESPMG computer codes are used to produce the response matrix and the response function of the detector, respectively. FORIST code was, then, used to unfold the neutron spectrum from the pulse height spectrum of proton. In the theoretical section, the neutron energy spectrum is calculated, in Monte Carlo method, using MCNP-4C code. Finally the results from two sections are compared. In the experimental section of this project, the energy spectrum of fast neutrons is measured, after being passed through large blocks, approximately lm3 each, of graphite, aluminium, water and paraffin. Neutrons were produced via 7Li(p,n)7Be reaction by bombarding a Lithium target with 25 or 30 MeV protons of the cyclotron at the Nuclear Research Centre for Agriculture and Medicine in Karaj. Measurements are done using a 76 × 76mm NE-213 scintillator detector, in two points outside the blocks, one in the direction of proton beam and the other normal to it. In analyzing the results of the experiments, SCINFUL and RESPMG computer codes are used to produce the response matrix and the response function of the detector, respectively. FORIST code was, then, used to unfold the neutron spectrum from the pulse height spectrum of proton. In the theoretical section, the neutron energy spectrum is calculated, in Monte Carlo method, using MCNP-4C code. Finally the results from two sections are compared.https://ijpr.iut.ac.ir/article_1486_fd6c3b383df946598e6f119d1d87c4f1.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202Elastic scattering of the halo nucleus 6 He from 197 Au at Elab=27 MeVElastic scattering of the halo nucleus 6 He from 197 Au at Elab=27 MeV23331487FAO. R. KakueeJ. RahighiH. AfaridehS. CherubiniT. DavinsonW. GalsterA. M. LairdM. Lamehi-RachtiP. OliaiyA. C. ShotterF. ShokouhiW. B. SmithJournal Article20200202 A radioactive ion beam of 6He produced via the 7Li(p,2p)6He reaction with typical intensity of 3 × 106 ions/see was elastically scattered from LiF(Au) targets. Elastic scattering of 6He at Elab=27 MeV with 197Au have been measured in the angular range of 6º-72º in the laboratory system employing LEDA and LAMP detection system. Optical Model calculations have been used to fit the data . A radioactive ion beam of 6He produced via the 7Li(p,2p)6He reaction with typical intensity of 3 × 106 ions/see was elastically scattered from LiF(Au) targets. Elastic scattering of 6He at Elab=27 MeV with 197Au have been measured in the angular range of 6º-72º in the laboratory system employing LEDA and LAMP detection system. Optical Model calculations have been used to fit the data .https://ijpr.iut.ac.ir/article_1487_65502ef0ed28ffaa13e42c639c0ca586.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202Excited states energy corrections of hydrogen atom at the order of & alpha4 using NRQED as an effective field theoryExcited states energy corrections of hydrogen atom at the order of & alpha<sup>4</sup> using NRQED as an effective field theory33401488FAS. M. ZebarjadM. BigdeliJournal Article20200202 In this paper, we calculate Hydrogen hyperfine splitting (HFS) at the order a4 by using NRQED as an effective field theory. We also show the leading-order contribution of nuclear size to the energy correction of Hydrogen atom . In this paper, we calculate Hydrogen hyperfine splitting (HFS) at the order a4 by using NRQED as an effective field theory. We also show the leading-order contribution of nuclear size to the energy correction of Hydrogen atom . https://ijpr.iut.ac.ir/article_1488_a21e0c590c668a27af8e197c47b5d850.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202Stability of solitary solutions to the cubic-quintic nonlinear Schrodinger equation (CQNLSE)Stability of solitary solutions to the cubic-quintic nonlinear Schrodinger equation (CQNLSE)41471489FAM. M. GolshanM. MoradiJournal Article20200202Analytical investigation of the stability of solitary solutions to the Cubic-Quintic Nonlinear Schr ö dinger Equation (CQNLSE), which governs the propagation of electromagnetic fields in nonlinear fibers, is the main subject of this article. Assuming a perturbation of the form in the solutions and using the theory of operators, we show that for CQNLSE , is pure imaginary so that such perturbations do not destroy the stability of the solutions. We also introduce a Hamiltonian, from which CQNLSE is derivable, and calculate its first and second order variations under the aforementioned perturbation. It is shown that the first order variation vanishes and the second one is positive, which is a further indication of the stability of the solutions .Analytical investigation of the stability of solitary solutions to the Cubic-Quintic Nonlinear Schr ö dinger Equation (CQNLSE), which governs the propagation of electromagnetic fields in nonlinear fibers, is the main subject of this article. Assuming a perturbation of the form in the solutions and using the theory of operators, we show that for CQNLSE , is pure imaginary so that such perturbations do not destroy the stability of the solutions. We also introduce a Hamiltonian, from which CQNLSE is derivable, and calculate its first and second order variations under the aforementioned perturbation. It is shown that the first order variation vanishes and the second one is positive, which is a further indication of the stability of the solutions .https://ijpr.iut.ac.ir/article_1489_486c83d7b9cea99e793ebf6445351d64.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202Semieptonic weak decay of B to D and D*Semieptonic weak decay of B to D and D<sup>*</sup>49541490FAM. HaghighatM. MomeniJournal Article20200202 In this paper we consider the Beth-Salpeter(BS) equation for the bound state of two piont particles with a confining kernal. Subsequently we obtain the heavy meson wave function in the framework of heavy quark effective theory assumptions. We calculate the semileptonic weak decay of B to D and D * using the BS wave function to give q2-dependence of the form factors. The obtained results for the from factors, their slopes and curvature are consistent with the experimental data. In this paper we consider the Beth-Salpeter(BS) equation for the bound state of two piont particles with a confining kernal. Subsequently we obtain the heavy meson wave function in the framework of heavy quark effective theory assumptions. We calculate the semileptonic weak decay of B to D and D * using the BS wave function to give q2-dependence of the form factors. The obtained results for the from factors, their slopes and curvature are consistent with the experimental data.https://ijpr.iut.ac.ir/article_1490_dee970e4dc5884d741741a48da008b7f.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202The calculation of the conductance and electron tunneling characteristic time from metal-molecule contact in a molecular wireThe calculation of the conductance and electron tunneling characteristic time from metal-molecule contact in a molecular wire55631491FAS. A. KetabiN. ShahtahmasebiJournal Article20200202 In this paper, on the basis of tight-binding model and a generalized Green- function method as well as Lanczos algorithm procedure, the effects of the metal-molecule coupling(MMC) strength on the electronic transmission through a metal-single molecule-metal(MMM) system is investigated. Using the Landauer formalism we study some of the significant conductance properties of this system as a molecular wire. Our results show that with the increase of the length of the molecule, the conductance of the molecular wire decreases exponentially. With trans-polyacetylene (trans-PA) as the molecule, we calculate a characteristic time for electron transmission through the MMM system. This time scale measures the delay caused by tunneling through the MMC. Our calculations show that the conductance is sensitive to the MMC strength. The focus is on the significant relationship between this time scale and the strength of the metal-molecule(trans-PA) coupling. In this paper, on the basis of tight-binding model and a generalized Green- function method as well as Lanczos algorithm procedure, the effects of the metal-molecule coupling(MMC) strength on the electronic transmission through a metal-single molecule-metal(MMM) system is investigated. Using the Landauer formalism we study some of the significant conductance properties of this system as a molecular wire. Our results show that with the increase of the length of the molecule, the conductance of the molecular wire decreases exponentially. With trans-polyacetylene (trans-PA) as the molecule, we calculate a characteristic time for electron transmission through the MMM system. This time scale measures the delay caused by tunneling through the MMC. Our calculations show that the conductance is sensitive to the MMC strength. The focus is on the significant relationship between this time scale and the strength of the metal-molecule(trans-PA) coupling.https://ijpr.iut.ac.ir/article_1491_39fd0a7ecf2389251a02ac22a7b472ab.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202Anomalous behavior of magnetostriction and magnetic ac-suseptibility of Gd1-xPrxCo5 polycrystalsAnomalous behavior of magnetostriction and magnetic ac-suseptibility of Gd<sub>1-x</sub>Pr<sub>x</sub>Co<sub>5 </sub>polycrystals65741492FAA. AmirabadizadehN. TajaborF. PourarianH. SalamatiJournal Article20200202Magnetostriction and low field ac-susceptibility of polycrystalline Gd1-xPrxCo5 (x = 0, 0.1 and 0.5) alloys are measured in temperature region of 77-300 K. XRD patterns show that our samples are single phase. For x = 0 (GdCo5) there are no anomaly in temperature dependence of magnetostriction and ac-susceptibility curves. For x = 0.1 and 0.5 temperature dependence of ac-susceptibilities show easy-axes phase transitions. In the case of x = 0.1 sample, the easy-axes of magnetization changes from canted to axial (practically, hexagonal c-axis) direction as temperature increases, and ac-susceptibility of x = 0.5 sample shows two iterative transitions, first from basal to canted then canted to axial. Magnetostriction of Pr contained samples anomalously decreases at spin reorientation regions.Magnetostriction and low field ac-susceptibility of polycrystalline Gd1-xPrxCo5 (x = 0, 0.1 and 0.5) alloys are measured in temperature region of 77-300 K. XRD patterns show that our samples are single phase. For x = 0 (GdCo5) there are no anomaly in temperature dependence of magnetostriction and ac-susceptibility curves. For x = 0.1 and 0.5 temperature dependence of ac-susceptibilities show easy-axes phase transitions. In the case of x = 0.1 sample, the easy-axes of magnetization changes from canted to axial (practically, hexagonal c-axis) direction as temperature increases, and ac-susceptibility of x = 0.5 sample shows two iterative transitions, first from basal to canted then canted to axial. Magnetostriction of Pr contained samples anomalously decreases at spin reorientation regions.https://ijpr.iut.ac.ir/article_1492_9024c7068c7d1b093c834f6a5f804b48.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202A new model based on group theory for correlating vibrational displacement vectors of attached atoms and shapes of the central atom otbitals in ABn(n=2-5) moleculesA new model based on group theory for correlating vibrational displacement vectors of attached atoms and shapes of the central atom otbitals in AB<sub>n(n=2-5) </sub>molecules75831493FAR. TayebeeJournal Article20200202 Stretching and bending normal vibrations of AB2(C2v), AB3(D3h), AB4(D4h), and AB5(D3h) molecules are described by correlating the vibrational displacement vectors of the attached atoms with the standard representations of s, p and d atomic orbitals of the central atom in ABn(n=2-5) molecules. It is found that stretching and bending normal vibrations of simple molecules accord with probability density of hybrid orbitals of the central atom. So, stretching and bending normal vibrations can be determined based on the irreducible representations of each vibration, and symbols for the representations which are suggested by Muliken. Stretching and bending normal vibrations of AB2(C2v), AB3(D3h), AB4(D4h), and AB5(D3h) molecules are described by correlating the vibrational displacement vectors of the attached atoms with the standard representations of s, p and d atomic orbitals of the central atom in ABn(n=2-5) molecules. It is found that stretching and bending normal vibrations of simple molecules accord with probability density of hybrid orbitals of the central atom. So, stretching and bending normal vibrations can be determined based on the irreducible representations of each vibration, and symbols for the representations which are suggested by Muliken.https://ijpr.iut.ac.ir/article_1493_3d86c00fd5ed1372c0afe861424d0599.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202The role of charge symmetry breaking in binding energy difference of 17F17O, 15O-15N mirror nucleiThe role of charge symmetry breaking in binding energy difference of <sup>17</sup>F<sup>17</sup>O,<sup> 15</sup>O-<sup>15</sup>N mirror nuclei85901494FAM. AsghariJournal Article20200202 Charge symmetry breaking potentials due to the exchange of pseudoscalar and vector mesons in mirror nuclei are considered. With the computation of coulmb energy along with the present charge symmetry breaking effects provide a reasonably accurate description of the binding energy differences between mirror nuclei. Charge symmetry breaking potentials due to the exchange of pseudoscalar and vector mesons in mirror nuclei are considered. With the computation of coulmb energy along with the present charge symmetry breaking effects provide a reasonably accurate description of the binding energy differences between mirror nuclei.https://ijpr.iut.ac.ir/article_1494_5400365c297a52a0f0b72ea23ab570da.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202Evaluation of resonant tunneling transmission coefficient from multilayer structures GaAlAs/GaAsEvaluation of resonant tunneling transmission coefficient from multilayer structures GaAlAs/GaAs91981495FAL. MoghaddasiA. Morteza AliR. Sabet-DarianiJournal Article20200202 A theoretical study of resonant tunneling in multilayered GaAlAs/GaAs structures are presented. The spectrum of resonant energies and its dependence on the barrier structure are analyzed from calculated profiles of barrier transparency versus energy, and from current voltage characteristics computed at selected temperatures and Fermi levels. The present formalism is based on the effective mass approximation and results are via direct numerical evaluations. A theoretical study of resonant tunneling in multilayered GaAlAs/GaAs structures are presented. The spectrum of resonant energies and its dependence on the barrier structure are analyzed from calculated profiles of barrier transparency versus energy, and from current voltage characteristics computed at selected temperatures and Fermi levels. The present formalism is based on the effective mass approximation and results are via direct numerical evaluations.https://ijpr.iut.ac.ir/article_1495_910b6b35922e94c4f15ee2ed75998efc.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202Size reduction of the transfer matrix of two-dimensional Ising and Potts modelsSize reduction of the transfer matrix of two-dimensional Ising and Potts models99991496FAM. GhaemiG. A. ParsafarJournal Article20200202 A new algebraic method is developed to reduce the size of the transfer matrix of Ising and three-state Potts ferromagnets on strips of width r sites of square and triangular lattices. This size reduction has been set up in such a way that the maximum eigenvalues of both the reduced and the original transfer matrices became exactly the same. In this method we write the original transfer matrix in a special blocked form in such a way that the sums of row elements of a block of the original transfer matrix be the same. The reduced matrix is obtained by replacing each block of the original transfer matrix with the sum of the elements of one of its rows. Our method results in significant matrix size reduction which is a crucial factor in determining the maximum eigenvalue. A new algebraic method is developed to reduce the size of the transfer matrix of Ising and three-state Potts ferromagnets on strips of width r sites of square and triangular lattices. This size reduction has been set up in such a way that the maximum eigenvalues of both the reduced and the original transfer matrices became exactly the same. In this method we write the original transfer matrix in a special blocked form in such a way that the sums of row elements of a block of the original transfer matrix be the same. The reduced matrix is obtained by replacing each block of the original transfer matrix with the sum of the elements of one of its rows. Our method results in significant matrix size reduction which is a crucial factor in determining the maximum eigenvalue.https://ijpr.iut.ac.ir/article_1496_3efdcb85a8f2382da5ba6ae4180fee2e.pdfIsfahan University of Technology,
The Physics Society of IranIranian Journal of Physics Research1682-69574120200202Quantum size correction to the work function and the centroid of excess charge in positively ionized simple metal clustersQuantum size correction to the work function and the centroid of excess charge in positively ionized simple metal clusters1001001497FAM. PayamiJournal Article20200202 In this work, we have shown the important role of the finite-size correction to the work function in predicting the correct position of the centroid of excess charge in positively charged simple metal clusters with different values . For this purpose, firstly we have calculated the self-consistent Kohn-Sham energies of neutral and singly-ionized clusters with sizes in the framework of local spin-density approximation and stabilized jellium model (SJM) as well as simple jellium model (JM) with rigid jellium. Secondly, we have fitted our results to the asymptotic ionization formulas both with and without the size correction to the work function. The results of fittings show that the formula containing the size correction predict a correct position of the centroid inside the jellium while the other predicts a false position, outside the jellium sphere. In this work, we have shown the important role of the finite-size correction to the work function in predicting the correct position of the centroid of excess charge in positively charged simple metal clusters with different values . For this purpose, firstly we have calculated the self-consistent Kohn-Sham energies of neutral and singly-ionized clusters with sizes in the framework of local spin-density approximation and stabilized jellium model (SJM) as well as simple jellium model (JM) with rigid jellium. Secondly, we have fitted our results to the asymptotic ionization formulas both with and without the size correction to the work function. The results of fittings show that the formula containing the size correction predict a correct position of the centroid inside the jellium while the other predicts a false position, outside the jellium sphere.https://ijpr.iut.ac.ir/article_1497_3287bb5ab4a413e1556e2df57236cf74.pdf