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قسم الفيزياء والفلك

PHYSICAL REVIEW A 83, 042502 (2011)
First and second derivative of the wave function of the 1_+ states of the KH molecule
Neji Khelifi*
King Saud University, College of Science, Physics and Astronomy Department, P.O. Box 2455, Riyadh 11451, Saudi Arabia
(Received 24 December 2010; published 5 April 2011)
 
Abstract
First and second derivative of the nonadiabatic coupling between the several 1_+ adiabatic states of the KH molecule considered from accurate diabatic and adiabatic data have been evaluated. Such derivatives of the electronic wave function are determined through a numerical differentiation of the rotational matrix connecting the diabatic and adiabatic representations. The first as well as the second derivative present many peaks related to ionic-neutral and neutral-neutral coupling between the 1_+ states. Such radial coupling has been exploited to calculate the first adiabatic correction, which corresponds to the diagonal term of the second derivative divided by the reduced mass, for the ground and some excited states of the KH molecule. The second adiabatic correction has been determined using the virial theorem. The first adiabatic correction was added to the adiabatic potential energy curves to redetermine the corrected spectroscopic constants and vibrational energy levels. The vibrational shift, which is the difference between the corrected and the adiabatic levels, has been calculated for X, A, C, and D 1_+ states of the KH molecule. A shift of some 10 cm−1 is observed for some vibrational levels showing the breakdown of the Born-Oppenheimer approximation.
 
Optics & LaserTechnology43 (2011) 147–151
 
External energy transfer in amplified spontaneous emissions
from MEH-PPV conjugated polymer
Mohamad S. Alsalhi n, Ziyad S. Abu Mustafa, V. Masilamani
King Saud University, Physics and Astronomy Department, Laser Group, College of Science, P.O. Box 2455, Riyadh 11451, Saudi Arabia
 
Abstract
We observed amplified spontaneous emissions (ASEs) in solutions of conjugated polymer under high power neodymium-doped yttrium aluminum garnet (Nd:YAG) laser excitation. A solution of coumarin- 485 dye (C485) and conjugated polymer (MEH-PPV) was prepared in tetrahydrofuran (THF). Here, C485 acted as a donor (with different ratios) while MEH-PPV served as an acceptor (with a constant ratio). Without the donor, MEH-PPV exhibited ASE only in the excimeric state; with the donor, however, it produced ASE in both the monomeric and excimeric states simultaneously. These results clearly show that it is possible to monitor and manipulate the excited state behavior of molecules by using an energy transfer process using laser-excited conjugated polymer.

Theoretical study of the 1, 3å+states of NaH molecule
 in adiabatic and diabatic representations
 
Neji Khelifi
King Saud University, College of Science
Physics and Astronomy Department
PO Box 2455, Riyadh 11451, Saudi Arabia
E-mail :khlifineji@yahoo.fr
Abstract

Adiabatic and diabatic study for all the states dissociating below the ionic limit [i.e., Na (3s, 3p, 4s, 3d, 4p, 5s, 4d and 4f) + H (1s)] in 1å+and 3å+symmetries are presented in this paper. Adiabatic results are also reported for 1, 3Pand 1, 3Dsymmetries. Pseudo-potential, operatorial core valence correlation and full valence CI approaches, combined to an efficient diabatization procedure are used in these ab initio calculations. Our vibrationel level spacings and spectroscopic constants are in good agreement with the available experimental data for the low-lying states. Diabatic potentials and dipole moments are analysed, revealing the strong imprint of the ionic state in the 1å+ adiabatic states. The H electron affinity correction was accounted for by the use of the efficient diabatization method. This leads to a better agreement with the available experimental data. Experimental suggestions are also given for the higher excited states based on their unusual behaviour.
Keywords:diabatic potentials, adiabatic potentials, dipole moments, ionic limit, pseudo-potential,operatorial core valence, correlation, full valence CI approach, vibrational levels, spectroscopic constants, potential energy curves.
 
Influence of atomic hydrogen annealing on the optical properties of vacuum-deposited a-Si:H films
 
A. M. El-Naggar†,*, and A. M. Al-Dhafiri
 
          Physics and astronomy department, Faculty of Science, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia.
   †Permanent address: Physics department, Faculty of Science, Ain Shams University, Abassia, Cairo 11566, Egypt.
 
Abstract
     The influence of atomic hydrogen in annealing of a-Si:H films on its optical parameters was studied using spectrophotometric measurements of the film transmittance and reflectance in the wavelength range 200 – 3000 nm. In this annealing, the deposition of a thin layer and treatment with atomic hydrogen were repeated alternately, where both the thickness of the thin cyclic layer,dcyc, and the treatment time for each cycle ,tca, were kept fixed for each sample. A series of different samples with average thickness of 0.5 μm were prepared with different dcycand tca. It was found that the refractive index, n, and the optical energy gap,Eg, increase as the treatment time,tca, increases from 0 to 60 seconds, while at tca= 120 second both n & Egdecrease.  Also, both the refractive index and the optical energy gap decrease with increasing the relative diffusion length of hydrogen,  from 0.39 to 0.77.The widening of Egis due to the structural relaxation resulting from impingement of atomic hydrogen on the growing surface. So, a good quality a-Si:H with Urbach parameter 65 mev and optical energy gap of 1.78 eV was successfully prepared.
 
Monte-Carlo simulations of elastically backscattered neutrons from hidden explosives using three different neutron sources
I. ElAgib a,_, N. Elsheikh b, H. AlSewaidan a, F. Habbani c
a College of Science, King Saud University, P.O. Box 2455, Saudi Arabia
b College of Applied & Industrial Science, University of Juba, Khartoum, P.O. Box 321, Sudan
c Faculty of Science, Physics Department, University of Khartoum, Khartoum, P.O. Box 321, Sudan
 
a b s t r a c t
Calculations of elastically backscattered (EBS) neutrons from hidden explosives buried in soil were performed using Monte-Carlo N-particle transport code MCNP5. Three different neutron sources were used in the study. The study re-examines the performance of the neutron backscattering methods in providing identification of hidden explosives through their chemical composition. The EBS neutron energy spectra of fast and slow neutrons of the major constituent elements in soil and an explosive material in form of TNT have shown definite structures that can be used for the identification of a buried landmine.
 
Journal of Russian Laser Research, Volume 30, Number 2, 2009
 
Theoretical study of the electronic structure of the
LiNa and LiNa+ molecules
 
King Saud University, College of Science
Physics and Astronomy Department
PO Box 2455, Riyadh 11451, Saudi Arabia
 
E-mail: khlifineji@yahoo.fr
 
Abstract
Adiabatic potential energy, spectroscopic constants, dipole moments and vibrational levels of the lowest electronic states of the alkali dimer LiNa molecule dissociating into Na (3s, 3p, 4s, 3d and 4p) + (Li (2s, 2p, 3s and 3p) in1, 3å, 1, 3P  and 1, 3Dsymmetries,are presented in this paper.Adiabatic results are also reported for 2S, 2Pand 2Delectronic states of the molecular ionLiNa+ dissociating into Li (2s, 2p, 3s and 3p) + Na+ and Li+ + Na(3s, 3p, 4s, 3d and 4p). We have used an ab initio approach involving a non-empirical pseudopotential for the Li (1s2) and Na (1s22s22p6) cores and core valence correlation correction. A very good agreement has been obtained for some lowest states of the LiNa and LiNa+ molecules for spectroscopic constants with the available theoretical works. The existence ofNumerous avoided crossing between electronic states of 2Σ and 2Π symmetriesare related to the charge transfer process between the two ionic systems Li+Na and LiNa+.
Keywords:adiabatic representation, pseudo-potential, operatorial core valence, correlations, full-valence CI approach, spectroscopic constants, potential energy curves, crossings, neutral, ionic limit,vibrational levels, spacings, dipole moments.
 
Acknowledgments
The study was supported by the College of Science at the King Saud University under the ResearchCenter Project No. Phys/2009/46.

Preparation and study of the magnetic and electrical properties of nano-particle Fe3O4doped MgB2superconductors

Mohammed Shahabuddin, Department of Physics and Astronomy, College of Science, King Saud University
Nasser Saleh Alzayed, Department of Physics and Astronomy, College of Science, King Saud University
Abstract

Nano particle size Fe3O4 (n-Fe3O4) doped MgB2 Samples were prepared by vacuum annealing at 750 0C for two and half hour. XRD measurement shows that the all samples are nearly single phase. The variation of lattice parameter 'a' shows maxima at 4% of doping level while the 'c' parameter shows maxima and minima at 2% and 4% of the doping level respectively. Despite the strong ferromagnetic nature of the doping, Fe3O4, the ac susceptibility and resistivity measurement shows that the depression in TC is around 6K up to 6% of the doping level. This indicates that the Fe is not substituted at either Mg or a B site rather it has occupies the inter-grain spaces. Magnetization measurements were carried out in doped and pure MgB2.  Even the strong ferromagnetic nature of the Fe, the n-Fe3O4 doped MgB2 up to 1% shows large increase in Jcwith respect to the virgin MgB2 samples in the lower field and temperature range (T < 20 K and H < 2 T). While in the higher field range (H > 2 T) JC of the n-Fe3O4 doped samples is always less than the virgin samples. The irreversibility line decreases drastically with increasing the concentration of the doping with respect to the virgin samples. Large increase in the Jc in lower temperature and field range shows that the n-Fe3O4 doping enhances the flux pinning.  In the lower range of doping level (<=1%) the magnetic activation i.e. the interaction between the magnetic dipole of Fe ion and the vortices, is weak in comparison to the effective pinning potential. While in the higher field rang the magnetic activation is dominant in comparison to the effective pinning potential provide by the doping. Flux jumps are also very clear in lower T and H region for the samples doped up to 1%. It is absent in the sample doped with n-Fe3O4 more than 1%. This shows that fluxiod jumps are intrinsic to the high Jc samples.
 
The effect of nano-alumina on structural
and magnetic properties of MgB2
superconductors
Intikhab A Ansari1, M Shahabuddin1,2, Khalil A Ziq3, A F Salem3,
V P S Awana4, M Husain1 and H Kishan4
1 Department of Physics, Jamia Millia Islamia (Central University), New Delhi 110025, India
2 Department of Physics, College of Science, King Saud University, PO Box-2455, Riyadh
11451, KSA
3 Department of Physics, College of Science, King Fahad University of Petroleum and
Minerals, Dehran, KSA
4 National Physical Laboratory, Dr K S Krishnan Marg, New Delhi 110012, India
Abstract
Nano-Al2O3 doped Mg1−xAlxB2 with 0 _ x _ 6% were synthesized by solid state reaction at 750 ◦C in Fe tube encapsulation under a vacuum of 10−5 Torr. Resistance measurement shows that the Tc decreases with x and zero resistivity for x = 0 and 6% are obtained at 38 and 35 K, respectively. XRD measurement shows that the lattice parameter and cell volume also decrease monotonically with increasing doping levels. From this we infer that the Al has been substituted in the lattice of MgB2 at Mg sites. Resistivity measurement shows a systematic decrease in Tc with doping which also confirms the substitution of Al. Magnetization studies in the temperature range from 4 to 35 K and in the magnetic field up to 9 T shows a significant increase in the irreversibility field (Hirr), critical current density (Jc) and remanent magnetization (MR) with increasing concentration of the Al2O3 nanoparticle. At low fields we have observed large vortex instabilities (known as a vortex avalanche) associated with all doped samples. The vortex-avalanche effect is reduced with increasing temperature and vanishes near 20 K. The results are discussed in terms of local-vortex instabilities caused by doping of Al2O3 nanoparticles.
 
Int. J. Nanoparticles, Vol. 2, Nos. 1/2/3/4/5/6, 2009, p. 372
 
Nano-carbon substitution effect on electrical and magnetic properties of Magnesium Diboride superconductors
 
Nasser Saleh Alzayed, Department of Physics and Astronomy, College of Science, King Saud University
Mohammed Shahabuddin, Department of Physics and Astronomy, College of Science, King Saud University
Abstract
Improving transport properties of polycrystalline MgB2 by nano particle doping has been widely studied by researchers. We have investigated the effect of nano-carbon (as amorphous C) doping on the critical current density (JC) of bulk MgB2 by measuring the ac susceptibility using locally made susceptometer. Nano C doped Mg(B1-XCX)2samples were synthesized with X varying from 0 to 10% by solid state  reaction method. All samples in the present investigation have been subjected to structural characterization employing x-rays diffraction (XRD), electrical measurement (using the four-probe technique) and ac susceptibility measurements using homemade ac susceptometer. The (XRD) investigations revealed that the structure of MgB2 is hexagonal with lattice parameter ( a = 3.0862 Å and c = 3.5256 Å for pure sample) and there were a contraction in the a-lattice parameter while the c- lattice parameter still unchanged for doped samples . This means that the carbon nano-particles are successfully soluble in MgB2.These nano-particles may enhance critical current density and the flux pinning centers. So, In order to study the flux pinning effect of C doping in MgB2, the evaluation of   critical current density (JC) has been carried out through magnetic measurements on the fine powdered version of the as synthesized samples according to Bean model. Finally we calculated the flux pinning parameter (n) for all samples to compare them. We found that the n parameter increased with increasing of the carbon content till 4% , then decreased. The optimum result with 4% means that adding more than this ratio may decrease the flux pinning force and the samples may become deteriorated even though they still superconductors
 
Design and Fabrication of High sensitive AC Susceptometer
Supercond. Sci. Technol. 20, 827–831 (2007)
Mohammed Shahabuddin, Department of Physics and Astronomy, College of Science, King Saud University
Nasser Saleh Alzayed, Department of Physics and Astronomy, College of Science, King Saud University
 
Abstract
The aim of the project was to develop the high sensitive ac susceptometer for closedcycle helium cryostat. We achieve our goal and now it is routinely used for the ac susceptibility measurements of high Tc superconductors, such as MgB2, YBaCuO and othermaterials. The design of the low cost ac susceptometer using closed cycle helium cryostat(CCHC)having helium gas exchange sample well is presented here. We elaborated the problems encountering the design of it. The problem of higher frequency limitation generally in CCHC has been solved up to some extent. The another problem is the balancing of offset voltage. We adopted simple technique to cancell the offset voltage. The nullification of the offset voltage up to 100 nV is achieved simply sliding the secondary inside the primary. This increases the sensitivity of bridge. The ac susceptometer was fabricated as per the design. The whole systems can be inserted and taken out through the gate valve of the sample well of the CCHC so that it dose not effect the other sample holders for different measurement. Our susceptometer is simple to use. The sample insert has been so designed that the changing of the samples of measurement is easy and quick.
 
22nd European Photovoltaic Solar Energy Conference, 3-7 September 2007, Milan, ItalyPHYSICAL PROPERTIES OF CdS THIN FILMS ON FLEXIBLE SUBSTRATES FOR OPTOELECTRONIC APPLICATIONS
F.M. Amanullah, A.S. Al-Shammari†, A.M. Al-Dhafiri, and U.A. Elani
Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455,
Riyadh-11451. Saudi Arabia. E-mail: aman@ksu.edu.sa,
†Department of Physics, College of Science, University of Hail, P.O. Box 2440, Hail, Saudi Arabia.
ABSTRACT: CdS thin films were prepared by vacuum evaporation technique at room temperature on flexible substrates like PVC, view foiles and papers. As deposited films exhibited high resistivity. Low resistive films have been obtained using the dopants like Cl and In. Electrical properties have been presented and discussed. The XRD pattern exhibits the presence of hexagonal CdS and orthorhombic CdCl2 structures respectively. The grain size of the films has been calculated. From the optical transmission studies, the optical band gap has been determined. The results reveal that the CdS films prepared on flexible substrates with appropriate dopants at room temperature have significant physical properties making them suitable for optoelectronic applications
 
Key words:Physical properties, doping, CdS thin films, flexible substrates.
 
Microstructural and electrical properties of amorphous carbon
nitride
M. Ben Karouia, R. Gharbia*, N. Elzayedb, M. Fathallahb, E. Tressoc
a Laboratoire des Semiconducteurs et des Dispositifs Electroniques. Ecole Supérieure des Sciences et Techniques de Tunis. 05 Av. Taha Hussein
1008, Montfleury. Tunis.Tunisia
b College of Sciences, King Saud University. P.O. Box 2455 Riyadh 11451. Saudi Arabia.
c Politecnico di Torino, 24 c.so Duca Degli Abruzzi ,10129, Torino. Italy
Elsevier use only: Received date here; revised date here; accepted date here
Abstract
Optical and electrical properties of amorphous carbon nitride (a-CN) have been investigated on films deposited by reactive R.F. sputtering method with a graphite target. Two series of a-CN samples were prepared using respectively the nitrogen (N2) or mixture of nitrogen and argon (Ar) as reactant gaz. In the two types of samples, the optical absorption increases with the target voltage bias and shifts to low energy. In the visible and near ultra violet range, the optical transitions are governed by the _ and _ * electronic state distributions, related to sp2 and sp1 hybridized C and N atoms. Specific lonepair electronic states arise from groups (CN) with sp1 hybridized C atoms, may form C_N triple bonds or —N=C=N— longer chains. Photoluminescence (PL) intensity depends on the microstructure in films but the PL peak does not change of its position at 1.85eV. The effect of nitrogen and target voltage bias on the optical and electrical properties was discussed in a-CN samples. The electrical properties of Schottky structures based on a-CN materials were characterized
 
PACS: 61.43.-j; 71.55.Jv; 72.80.Ng; 73.61.Jc.
Keywords: amorphous carbon nitride; microstructural; conductivity; photoluminescence ; Schottky barrier.
 
Thermoluminescence properties of P2O5-Li2O
glass systems doped with MgO and CuO
 
M.M. Elkholy1*, A. M.Al-Soraie2, and A.A. Yosuf2
 
1 Department of Physics, Faculty of Science, Menoufia University, Shibin Al-Koom, Egypt.
2  Department of Physics, College of  Science, King Saud University, Riyadh, KSA. 
خلاصة
تم تحضير عينات من زجاج فوسفات ليثيومِ وفقا للنظامِx = 20, 30, 40, 50, 60, 70 (100-x)P2O5 - xLi2O تم تطعيم العينات بنسب 10-1, 10-2, 10-3, 10-4، و10- 5MgO   وCuOوتم قياس منحنيات الوميض الحراري thermoluminescentلها. عمليات التشعيع تمت بواسطة استعمال أشعةِ جاما مِنْمصدر كوبالت -60في مدى الجرعةَ مِنْ   0.1 kGyإلى  20 kGy وقد أظهرت المادّةُ حسّاسيةً جيدةً لأشعةِ جاما. أظهرت القياسات أنّ الشدة النسبيةُ لمنحنيات الوميض الحراري تتناسب مع الجرعةِ الإشعاعية. وجد أيضا أن شدة الوميض الحراري معتمدة علىمحتوى أكسيد الليثيوم في النظام الزجاجي المحضر حيث وجد أنها تزداد بشكل ملحوظ وبشكل خطي تقريبا مع زيادة أكسيد الليثيوم.  لكُلّ مستويات الجرعات  في مدى درجةِ حرارة(100-350 oC)، تم رصد  قمّةَ وهجِ واحدة و محددة  في مدى درجةَ حرارة  208 oCإلى  257 oCبإعتِمادعلى كل من محتوى أكسيد الليثيوم  ووقت التعرّضِ الإشعاعي.أظهرت القياسات أن شكل قمّةِ الوهجَ لم تتغير بشكل ملحوظ بزيَاْدَة جرعةِ الإشعاع أَو  محتوى أكسيد الليثيوم  .المركب الزجاجي المحتوي على x = 70 mol %   المطعم بنسبة 10-3 mol % MgO  بالتمازج مع10-3 mol % CuO  أظهرت أفضل حساسية إشعاعية. إنّ نَتائِجَ الدراسةِ الحاليةِ على هذه العينة أشارتْ بأنّ المنحنيات  المسجّلَة لهاْ قمّةَ واحدة عند درجةِ حرارة عاليةِوالتي ترشحها لتكون مناسبة جدا لأغراض القياسات الإشعاعية في المدى المذكور.  
            Key words: Thermoluminescence, P2O5-Li2O, Glass, radiation dosimetry.
 
Annals of Physics xxx (2009) xxx–xxx
Perturbed Coulomb potentials in the Klein-Gordon equation via
the asymptotic iteration method
T. Barakat
Physics Department, King Saud University
Riyadh 11451, Saudi Arabia
 
The asymptotic iteration method is used to construct the exact energy eigenvalues for a Lorentz vector or Lorentz scalar, and an equally mixed Lorentz vector and Lorentz scalar Coulombic potentials.  Highly accurate and rapidly converging ground-state energies for Lorentz vector Coulomb with a Lorentz vector or a Lorentz scalar linear potential,
V(r)=-A/r+kr and V(r)=-A/r and W(r)=kr, respectively, are obtained.

Optics and Spectroscopy, 2012, Vol. 112, No. 6, pp. 874–880.
 
Elemental  Analysis  of  Fertilizer  Using  Laser Induced Breakdown  Spectroscopy1

    A.  Farooq,  F.  N.  AlMutairi,  A.  E.  M.  Khater,  A.  S.  Al-Dwayyan,
        S.  AlSalhi,  and  M.  Atif
 
Department of Physics and Astronomy College of Science, P.O. Box 2455, King Saud University, Riyadh 11451, Saudi Arabia
email:  wafarooq@hotmail.com,  atifhull@gmail.com
 
Received December 23, 2011
 
Abstract—In recent years, the use of fertilizers has increased to achieve high growth rate of agriculture products. With this increase the chemical impact of agricultural activities on the environment has also been enhanced. In order to keep the environment healthy, and clean, it is necessary to identify contaminants and characterize the sources of contamination. In this study, a comprehensive chemical characterization of a DAP fertilizer has been carried out using laser induced breakdown spectroscopy. Phosphorous, manganese, magnesium, iron, titanium, molybdenum, nickel, cobalt, aluminum, chromium, lead, and uranium traces are detected. Relative abundances of Phosphorous, manganese, magnesium, molybdenum, iron, titanium, nickel, vanadium, calcium, cobalt, cadmium, tin are 26.64, 17.75, 13 97, 8.25, 7.97, 7.11, 5.07, 3.15, 2.94, 1.94, 1,55, 1.73 percent, respectively, whereas relative abundances of sulfur, aluminum, chromium, lead, and uranium are less than 1% and their sum is 1.93% of the total sample.
 
DOI:  10.1134/S0030400X12060082

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