The energy levels have been calculated by using the nuclear shell model and adopting the surface delta interaction for the nuclei 34S, 34Ar and 34Cl with two additional nucleons which are located outside close core 32S. A comparison had been made between our theoretical predictions and the recent  available experimental data .  A reasonable agreement were obtained from these comparisons . Key words: shell model, energy levels, Surface delta interaction

Hasan, A.K.

Hussain, F.M.

English

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Advances in Physics Theories and Applications                                                                                                  www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013          128 Calculation of Energy Levels for Nuclei 34S,34Ar,34Cl by using Surface Delta Interaction A.K.Hasan1 ,  F.M.Hussain2 Department of Physics, College of Education for Girls, University of Kufa 1 Department of Physics, College of Education for Pure Sciences, University of Babylon 2  Abstract The energy levels have been calculated by using the nuclear shell model and adopting the surface delta interaction for the nuclei 34S, 34Ar and 34Cl with two additional nucleons which are located outside close core 32S. A comparison had been made between our theoretical predictions and the recent  available experimental data .  A reasonable agreement were obtained from these comparisons .  Key words: shell model, energy levels, Surface delta interaction.             1. Introduction  The nuclear shell model is one of the important and useful models that became mainstream theoretical model in the nuclear physics structure [1, 2]. In the model ,we fill the shells with in order of increasing energy, consistent with the requirement of the Pauli principle, when we do so, we obtain an inert core of filled shells and some number of valence nucleons, the model then assumes that nuclear properties are determined primarily by the valence nucleons [3]. In this paper, Surface delta interaction has been used as interaction residual in two nucleons by applying nuclear shell model to calculate the energy levels for three nuclei equivalent in mass numbers and different in nucleons type, these nuclei are: 34S18   , 34Ar16   and 34Cl17. The core taken at 32S with two nucleons distributed over  (0d3/20f7/2 ).   2. Theory  The shell model uses two principle assumptions are there exists an inert core, made of close shells, which acts with central force on valence nucleons and there exists a residual interaction caused by two body forces action between the valence nucleons [4]. Residual interaction is defined as the force that produces when nucleons collide with each other and this interaction is happen the perturbation in Hamiltonian operator that equal summing two particles potential and represent Hamiltonian operator to perturbation state from equation [5]:  (1)  ijV  is the residual two-body  interaction , H0 is represent Hamilton operator without perturbation. To calculate the spectrum of this nucleus we assume that the residual nucleon-nucleon interaction ijV  is the surface-delta potential (SDI) ,is given by [5]:- (2)    )(4 jrirVV −°−= δπ   Where 0V  is interaction strength and ir , jr  are the position vectors. This form was introduced by Green and Moszkowski has served as a remarkably good effective interaction for shell model calculations in many regions of the periodic table [6]. Tow -body matrix elements are given by [5]:      -       )43()21()43;21( jjJMijVjjJMjjjjJE ΨΨ=                (3)         And matrix element of SDI for two body outside core is given by following form [5]:   ∑〈+°= ji ijVHHAdvances in Physics Theories and Applications                                                                                                  www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013          129   +++−+×++++−−= 4321)1(1)12(44321)1()43;21(llllJRVjjjjjjjjJTE o (( ) ( ) 424211|2121431|212121}11{jjllJjjJjjT−++−+×−+× .                              (4) ( ){ } −−+++−−× 0|2121430|2121214311 JjjJjjllTJ Together with the restriction that the magnitude of the radial integrals involved be set equal to a constant ( ) ( ) ( ) ( ) drrrjRrjRrjRrjRR24321∫=  The matrix element as explicitly evaluated with wave functions that are positive at 0→r . 04321)1( RnnnnR+++−=  Where ni is the number of radial nodes for the state ji, R0 is appositive number and is the Clebsch- Gordon coefficients.        If je is the energy of the single –particle relative to the close core and );( jjjjJE  is the interaction energy when the two particles couple to angular momentum J the energy of this state relative to the closed shell is [5]:  (5)                );(2)()( jjjjJEjejjJMHjjJM +=ΨΨ   For simplicity assumes there are two state denoted by )21( jjJMΨ  and )43( jjJMΨ , then the energies with respect to the core are given by [5]:  ++=++=)43;43(4322)21;21(2111jjjjJEjjHjjjjJEjjHεεεε                                      (6a)               )43;21(2112 jjjjJEHH ==                                                 (6b)      Equation  (6a) calculates the energies for pure configurations and to calculate the energies in mixing configurations (6b) should be added to (6a). The allowable angular momentum states for two particles calculate from two theorems [5]: First theorem, if two identical particles in the same single particle orbit j (j half integer) can only couple their spins to even values of J: )12,......(4,2,0 += JJ                                                                      (7a)  But if two different particles the configuration (j) 2 have odd values of J (J=1, 3...) too. Second theorem, if two particles in the states j1 and j2 (j1≠j2) the allowable angular Momentum values are 21,.....121,21jjjjjjJ −−++=                                           (7b)   21)43431)(21211()142)(132)(122)(112(++++++×lljjlljjjjjjδδδδAdvances in Physics Theories and Applications                                                                                                  www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013          130 3. Calculation, Results and Discussion  In this work, the energy levels have been calculated for 34S, 34Ar and 34Cl in the model space (0d3/2 0f7/2) with allowed angular momentum J. 3.1. The even-even 34S, 34Ar nuclei.  In our calculations 32S is considered as the close core with 2 neutrons and 2 protons distributed over (0d3/20f7/2) outside the core for 34S and 34Ar, respectively. The single particle energies for 0d3/2, 0f7/2 are taken to be -8.643MeV, -5.709MeV for neutrons and -2.277MeV, -0.408MeV for protons [7, 8, 9]. From eq. (7a) and (7b) the allowed angular momentum states have been assigned for these nuclei are: J=0, 2, 3,4,5,6        A computer program written by Mathematica to calculate the matrix element of (SDI) residual interaction eq. (4), and hence the energy levels are calculated by using  eq. (6a) and (6b). The calculated levels spectra for 34S are compared with the recent available experimental data [9, 10, 11], as shown in Fig.1 with their values tabulated in Table 1. Good agreement was obtained for this nucleus in both, positive and negative states. If we focus our attention to the first  2+ from ground band, our work predicts this level at 2.385MeV which is very close to the value experiment, and we can notice the level 5-  in our work at 4.683MeV is deviated to some extent from the experiment value 5.689MeV, the difference between the two values is 1MeV. Fig.2 and table 2, in this work, each level from calculated energy levels for 34Ar in comparison with experimental data [9, 10, 11]. The comparison was obtained in good agreement, our calculations predict the first level 2+ from the ground band at 2.048MeV is in good agreement with experimental value is 2.09MeV. From this compare we can see that this model space in reasonable agreement with experiment up to J ≤ 6+.   Table 1 Comparison between calculated excitation energy levels with experimental data for 34S. Exp .Res. [9,10,11] Pre. Res.  ][MeVE  πJ  ][MeVE  πJ  0.0 0+ 0.0 01+ 2.127 2+  2.385 21+  5.689 5- 4.683 5-  5.679 3- 5.384 3-  5.68 2- 5.706 22- 6.251  4-  5.706 41-  6.685 (0)  6.346 02+  7.805 2+ 7.886 23+ 8.264 4+)(  8.245 42+  8.503 6+  8.443 6 +  Table 2 Comparison between calculated excitation energy levels with experimental data for 34Ar. Exp. Res. [9,10,11] Pre. Res. ][MeVE  πJ  ][MeVE  πJ  0.0 0+ 0.0 01+ 2.091 2+  2.048 21+  4.127 - 4.175 5-  4.513 4.865 3- - 4.789 3-  5.225 - 5.07 22  5.225  -  5.07 41-  5.909 0+ 5.710 02+  7.322 2+  7.093 23+ 7.499 (2+) 7.409 42+ 7.925 -  7.583 6+ Advances in Physics Theories and Applications                                                                                                  www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013          131   Fig .2- A comparison between theoretical energy levels and the experimental  values taken from [9,10,11] for 34S  Fig .2- A comparison between theoretical energy levels and the experimental  values taken from [9,10,11] for 34Ar. Advances in Physics Theories and Applications                                                                                                  www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013          132  3.2. The nucleus odd-odd represented by Chorine nucleus 34Cl. Nucleus 34Cl contains one proton and one neutron outside close core 32S distributed over the model space (0d3/20f7/2). The allowed angular momenta can be calculated by using eqs. (7a, 7b) are: J=0, 1,2,3,4,5,6,7  The calculation have been carried out using the effective interaction (SDI) eq.(4), and we depended the single particles energies for neutron and proton.  In fig.3 and table 3, present the comparison of results obtained in this work for 34Cl with experimental data [9,10,11]. From Fig.3 and Table 3, we can notice that this model is in good agreement with experiment up to 9.998MeV. Mixed arrangement adopted in our calculations,  we can see the increasing energy levels that conform well with the experimental data. As show the calculated first level 1+ at 1.567MeV, in this range no approach  experimental value. The higher value was obtained for this nucleus according to the recent available experimental is 8.793MeV, comparing with our calculations was obtained the level 3+ by 9.998MeV that exceed experimental data.   Table 3 Comparison between calculated excitation energy levels with experimental data for 34Cl. Exp. Res.  [9,10,11]   Pre. Res.  ][MeVE  πJ  ][MeVE  πJ  0.0 0+ 0.0 01+  - -  1.567 11+  2.181 3+ 1.811 31+ 2.158 2+ 2.469 21+  3.631 5͞ 3.181 51-  4.461 (3)͞ 4.397 32-  5.576  ) (2͞  5.55 22-  5.54 (4)  5.55 41- 5.785 3)(  5.680 52͞ 6.207 4(-)  5.799 42͞ 5.805 2͞ 5.801 23͞ 6.479 (0)  6.219 02+  6.991 1+ 6.964 12+ 7.061  -  7.089 7+ 7.677 3- 7.668 33͞  7.666  -  7.681 53+ 7.761 (2)+ 7.723 24+ 8.012 (4)+ 8.084 43+ 8.280  -  8.284 6 +   9.998 34+          Advances in Physics Theories and Applications                                                                                                  www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013          133  Fig.3- A comparison between theoretical energy levels and the experimental  values taken from [9,10,11] for 34Cl.  4. Conclusions The nuclear shell model calculations are in good agreement with the experimental data by adopting the surface delta interaction (SDI) as residual interaction with suitable single particle energies. Configuration mixing are taken into account and enhances the calculations of the excitation energies. These calculations can be repeated by adopting the modified surface delta interaction (MSDI) with suitable parameters adjusted for this mass region and might improve the calculations.   References [1] I. Kaplan, Nuclear Physics, Addison – Wesley Pub.Com. Inc, 1963. [2] N .D. Cook, Models of the Atomic Nucleus, Springer -Verlag Berlin Heidelberg Netherlands , (2006).                                                                                             [3] K.S. Krane, Introductory Nuclear Physics, John Wiley &Sons, Inc,(1988). [4] A. Jasielska, S.Wiktor,Acta.Phys. Pol., Vol. B7, No. 2, P133-140, (1976). [5] R .D. Lawson, Theory of the Nuclear Shell Model , Clarendon Press, Oxford,      (1980).      [6] K.T.Hecht, A. Adler, Nucl. Phys., A 137, 129-143 (1969).            [7] G. Audi, A.H. Wapstra, C. Tribally, Nucl. Phys., A 729, 337-676 (2003). [8] J. Chen, B. Singh, Nuclear Data Sheets, 112, 1393 (2011). [9] C.M. Leaderar, V.S. Shirley, Table of Isotopes, John Wiley &Sons Inc, (1978). [10] P.M. Endt, R.B. Firestone, Nucl. Phys., A 633, 1 (1998). [11] N. Nica, B.Singh, Nuclear Data Sheets, 113, 1563 (2012).     This academic article was published by The International Institute for Science, Technology and Education (IISTE).  The IISTE is a pioneer in the Open Access Publishing service based in the U.S. and Europe.  The aim of the institute is Accelerating Global Knowledge Sharing.  More information about the publisher can be found in the IISTE’s homepage:  http://www.iiste.org  CALL FOR PAPERS The IISTE is currently hosting more than 30 peer-reviewed academic journals and collaborating with academic institutions around the world.  There’s no deadline for submission.  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Calculation of Energy Levels for Nuclei 34S,34Ar,34Cl by using Surface Delta Interaction

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Calculation of Energy Levels for Nuclei 34S,34Ar,34Cl by using Surface Delta Interaction

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