Advances in High Energy Physics

Volume 2017, Article ID 1634717, 11 pages

https://doi.org/10.1155/2017/1634717

## Relativistic Energies and Scattering Phase Shifts for the Fermionic Particles Scattered by Hyperbolical Potential with the Pseudo(spin) Symmetry

^{1}Department of Physics, Federal University of Technology, Minna, Niger State, Nigeria^{2}Department of Physics, Federal University Oye-Ekiti, PMB 373, Ekiti State, Nigeria

Correspondence should be addressed to O. J. Oluwadare; gn.ude.eyouf@eradawulo.nihelimitawulo

Received 20 November 2016; Revised 19 December 2016; Accepted 10 January 2017; Published 5 February 2017

Academic Editor: Edward Sarkisyan-Grinbaum

Copyright © 2017 K. J. Oyewumi and O. J. Oluwadare. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The publication of this article was funded by SCOAP^{3}.

#### Abstract

In this paper, we studied the approximate scattering state solutions of the Dirac equation with the hyperbolical potential with pseudospin and spin symmetries. By applying an improved Greene-Aldrich approximation scheme within the formalism of functional analytical method, we obtained the spin-orbit quantum numbers dependent scattering phase shifts for the spin and pseudospin symmetries. The normalization constants, lower and upper radial spinor for the two symmetries, and the relativistic energy spectra were presented. Our results reveal that both the symmetry constants ( and ) and the spin-orbit quantum number affect scattering phase shifts significantly.

#### 1. Introduction

Scattering theory is very central to the study of several fields such as atomic, nuclear, high energy or condensed matter physics. It allows for descriptions and interpretations of many collisions processes such as excitation and ionization by particle or radiation impact [1–7]. Complete information about the quantum systems can only be obtained by investigating scattering state solutions of relativistic and nonrelativistic equations with quantum mechanical potential model.

As a result, several authors in quantum mechanics have strictly followed different approaches to study the scattering state solutions of the relativistic and nonrelativistic wave equations for central and noncentral potential models [8–15]. In their works, they have reported the calculations on phase shifts, transmission and reflection coefficients, resonances, normalized radial wave functions and properties of -matrix for potential models of their interest. All these are sufficient enough to predict, correlate, and describe the behaviour of particles.

However, literature revealed that the investigations on the spin and pseudosymmetries [16, 17] of Dirac equation, which was previously on the bound state problems [18–21], have now been extended to scattering state problems [22, 23]. Just of recent, under the spin and pseudospin symmetry, the analysis of scattering state solutions of Dirac equation with certain potential function models of interest were considered by some authors. These include Yukawa potential [22] and Hellmann potential [23].

This is owing to the fact that the symmetries in Hadron and nuclear spectroscopy [24] as well as deformation and superdeformation in nuclei [25] can be best understood by studying scattering state problems under pseudo(spin) symmetry. Among the various relativistic potential function models, we consider hyperbolical potential (Schiöberg potential), which was proposed by Schiöberg in 1986 [26] in order to find a more suitable empirical potential energy function for diatomic molecules. In 2012, Wang et al. [27] constructed an improved version of hyperbolical potential (called new Schiöberg potential) by employing the dissociation energy and the equilibrium bond length for a diatomic molecule as explicit parameters. As Jia et al. [28, 29] also reported that the new Schiöberg potential, Deng-Fan potential, and the Manning-Rosen potential are the same empirical potential energy functions.

In view of the above works, we are motivated to investigate the scattering state solutions of Dirac equation with hyperbolical potential suggested by Schiöberg in 1986 and apply an improved Greene-Aldrich approximation scheme within the formalism of functional analytical method. In the present study the new Schiöberg potential is ignored and we focus on the effects of the symmetry constants and the positive potential parameters on the relativistic energy and the scattering phase shifts of the hyperbolical potential (Schiöberg potential).

This paper is organized as follows: Section 2 contains the basic equation. In Section 3, we studied the approximate scattering state solutions for the hyperbolical potential in detail. The discussions and conclusions are given in Section 4.

#### 2. The Basic Equations

By considering the Dirac wave equation and its corresponding spinors, the two-coupled first-order differential equations for the upper and lower components of the spinor may be obtained as [30–33]where and . Solving for in (1) and in (2), we obtain the Schrödinger-like equations satisfying for upper radial spinor and lower radial spinor , respectively, aswhere and .

##### 2.1. Pseudospin Symmetry Limit for the Hyperbolical Potential

By following the pseudospin symmetry conditions and considering the hyperbolical potential satisfying relativistic model [34–37],where , , and are the three positive potential parameters that significantly affect the relativistic energy spectra and the relativistic scattering phase shifts. Schiöberg [26] reported that this potential is closely related to the Morse, the Kratzer, the Coulomb, and the harmonic oscillators and other potential functions in a particular limit. The properties and applications of this potential have been given by Lu et al. (2005) and Schiöberg (1986).

Under the pseudospin symmetry condition (4) yieldswhere and are the pseudospin symmetry energy parameters.

##### 2.2. Spin Symmetry Limit for the Hyperbolical Potential

In a similar way, we consider the spin symmetry conditions and take as hyperbolical potential [34–37]. That is,and using the spin symmetry conditions, (3) becomeswhere and denote spin symmetry energy parameters.

##### 2.3. Pekeris-Type Approximation

To obtain the approximate solutions in the presence of the spin symmetry and pseudospin symmetry, we use the Greene-Aldrich approximation [38] and apply the widely used scheme for the centrifugal term; namely,where is a dimensionless constant [39]. This approximation has been used to obtain the approximate analytical solutions of Dirac equation with the hyperbolic potential in the presence of spin symmetry and pseudospin symmetry [21]. When , this approximation reduces to the well-known Greene-Aldrich approximation [38]. Note that another approximation scheme has been proposed to overcome the effect of centrifugal term in [40]. Our interest here is to apply this improved Greene-Aldrich approximation and see whether the symmetry constants ( and ) and the spin-orbit quantum number will have any influence on the scattering phase shifts.

#### 3. Relativistic Scattering State Solutions

##### 3.1. Pseudospin Symmetry Limit for Hyperbolical Potential

Defining a variable and applying approximation in (9), then (6) reduces towith the following useful definitions:where is the asymptotic wave number for the pseudospin symmetry limit.

In order to solve (10) via the functional analytical method, we need to assume a wave functionwith the pseudospin wave function parameter . Inserting (12) into (10) leads to the formation of hypergeometric equation [41]

By considering the boundary condition that tends to finite when , the lower component of radial wave functions for any arbitrary -wave scattering states for the hyperbolical potential is obtained as [42]whereIt is required that we consider the following conjugate relations which define the asymptotic phases:and is the normalization.

###### 3.1.1. Pseudospin Symmetry Phase Shifts and Normalization Constant

To obtain the phase shifts and normalization constant, we apply the following recurrence relation of hypergeometric function or analytic-continuation formula [41]:Considering (17) and the property , as , we haveusing (16a), (16b), and (16c) we may transform (18) asBy taking and inserting in (19), we haveTherefore, we obtain the asymptotic form of the lower spinor for asOn comparison of (20) with the boundary condition [42]. Thus, we finally obtain the explicit pseudospin symmetry phase shifts and the normalization constant, respectively, as

###### 3.1.2. Analytical Properties of -Matrix for the Pseudospin Symmetry Limit

Here, the analytical properties of partial-wave -matrix are investigated to verify the fact that the poles of the -matrix in the complex energy plane correspond to bound states for real poles [42]; thus, we consider , where its first-order poles are at the point [42]Consequently, the bound state energy levels for the pseudospin symmetry limit are obtained as

##### 3.2. Spin Symmetry Limit for the Hyperbolical Potential

Using the previously defined transformation variable and approximation, (8) becomeswith the following spin symmetry phase parameters:where is the asymptotic wave number for the spin symmetry limit.

Similarly, we also assume the following upper wave function for the spin symmetrywith the spin symmetry wave function parameter .

To avoid repetition, we follow the same procedures in previous subsection and write the upper component of spin symmetry radial wave functions for any arbitrary -wave scattering states aswhere we have used the following wave function parameters:where is the normalization constant depending on and .

###### 3.2.1. Spin Symmetry Phase Shifts and Normalization Constant

Following the same steps in Section 3.1.1, we write the explicit spin symmetry phase shifts and the corresponding normalization constant, respectively, aswhere we have employed the following phase shifts parameters for simplicity:

###### 3.2.2. Analytical Properties of -Matrix for the Spin Symmetry Limit

Following the same fashion in Section 3.1.2, the corresponding bound state energy levels for the spin symmetry are determined by the following energy equation:

##### 3.3. Nonrelativistic Limit for the Scattering State Solution

To study the nonrelativistic limit, we apply the following appropriate mapping to (34):Consequently, we obtain the nonrelativistic bound state energy levels for any arbitrary aswhere .

#### 4. Discussion and Conclusion

The pseudospin symmetry bound states energy spectra displayed in Table 1 are obtained from (25) and the corresponding spin symmetry bound states energy spectra displayed in Table 2 are obtained from (34) while the nonrelativistic bound state energy spectra are obtained from (36). The pseudospin symmetry and spin symmetry phase shifts are obtained from (22) and (31), respectively.