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Examining the Angular Distribution of Deuteron Scattering from 6Li and 9Be in the Elastic Channel

Received: 9 June 2025     Accepted: 2 July 2025     Published: 7 August 2025
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Abstract

The theoretical analyses of the elastic scattering of deuteron from 6Li, and 9Be were performed in the optical model (OM) framework. The double-folding model with a density-dependent M3Y-type effective interaction was used to derive both the real and the imaginary components of the optical potential. The derived nuclear optical potentials were subsequently employed in the OM formalism to analyse the angular distribution data of deuteron scattering from 6Li, and 9Be at different incident energies. The calculated differential cross-sections were compared with experimental data across multiple incident energies. The results demonstrate that the derived potentials accurately reproduce experimental observables, confirming the reliability of the double-folding model and the OM for modelling light-ion scattering. These findings also underscore the applicability of the M3Y-type interaction in describing short-range nuclear interactions in light nuclei.

Published in International Journal of Applied Mathematics and Theoretical Physics (Volume 11, Issue 3)
DOI 10.11648/j.ijamtp.20251103.11
Page(s) 36-43
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This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2025. Published by Science Publishing Group

Keywords

Angular Distribution, Elastic Scattering, Folding Potential, Pseudo-Potential, M3Y-Type Interaction, S-Matrix

1. Introduction
The intricate many-body nature of nucleus-nucleus interactions remains a topic that is not yet fully understood. Continuous improvements are being made to theoretical models and techniques to tackle this complex problem . A key approach to advancing the understanding of the complex many-body problem of the nucleus-nucleus interaction involves a detailed analysis of experimental results within theoretical frameworks. Specifically, analysing heavy-ion data through models like the optical model, coupled channels, and coupled reaction channels yields valuable insights into the general features of nucleus-nucleus interactions, including their energy dependence and links to nuclear structure .
Heavy-Ion (HI) scattering is marked by strong absorption, which occurs when part of the incoming wave is diverted from the elastic scattering path into other, non-elastic channels . As a result, the optical potential used to describe HI interactions always includes an imaginary component. The real component accounts for elastic scattering, while the imaginary part represents absorption and the loss of flux from the elastic channel . Because of this strong absorption, only peripheral collision paths are useful in probing the real part of the nucleus-nucleus interaction, particularly near the nuclear surface . The radius where this surface interaction becomes significant is identified as the strong absorption radius.
Therefore, it has become particularly important to develop theoretical tools to investigate the nuclear structures and nuclear reactions of HI scattering. In recent times, the mass-dependent interactions dubbed the M3Y-type interactions, derived using the lowest order constrained variational approach, were constructed . The interactions were derived using nuclei of mass number A=16, 24, 40, and 90 . Although the strengths of the interactions showed mass dependence, it was recommended that they could be used in the study of nuclear structure and reactions for all nuclei.
The primary objective of this study is to derive optical potential parameters for the elastic scattering of deuteron from Li 6 and Be 9 nuclear system. The double folding model (DFM) was applied, employing the density-dependent version of the M3Y-type interaction to derive the strengths of the optical potential. The analyses of the differential cross-sections were done using a phenomenological optical model (OM) approach.
2. Materials and Methods
To construct the nuclear optical potential, the double-folding model was used. The double-folding model convolves the effective NN interaction with the nuclear density distributions of the projectile and target :
VFr=ρprpρtrtVptrtpdrpdrt(1)
here ρp and ρt are the density distributions of the projectile and target nuclei, and rtp=rt-rp and the term Vpt is the effective M3Y-type density-dependent interaction . The nuclear densities are modelled using the two-parameter Fermi (2pF) distribution :
ρr=ρ01+expr-ca-1(2)
here, ρ0, c, and a are the central density, the half-density radius, and the diffuseness parameter, respectively. The 2pF function was parametrised in the manner prescribed by , for both the incident and the target nuclei. The double folding model calculations were done using the folding model code of the Nuclear Reaction Video (NRV) .
The double-folded potential naturally represents the real part of the optical potential. To account for the imaginary part—which captures absorption into non-elastic channels—a similar folding approach was applied but with a different renormalization factor to obtain the nuclear optical potential in the form :
Ur=Nr+iNiVFr+VCoulr(3)
where Nr(i) are the real and imaginary renormalization factors for the folded potential and VCoulr is the Coulomb potential. These renormalization constants are adjusted to achieve optimal agreement with experimental data.
The optical potential formulation of Equation (3) was modified to include potential geometrical parameters. These geometrical parameters were assumed to have the Woods-Saxon form factor. The nuclear part of the OP of Equation (3) was modified to include the geometrical parameters in the form;
VN=-V0fr,Rv,av+iW0fr,Rw,aw (4)
where V0 and W0 are the strengths of the real and imaginary folded potentials, respectively, and fr,Ri, ai is the introduced Woods-Saxon form factor with i=v,w. The geometrical form factor introduced in Equation (4) is defined by ;
fr, Ri,ai=1+expr-Riai-1 (5)
where Ri and ai are the half-value radius and the diffuseness parameters, which describe the decreasing rate of the optical potential. The radius parameters were defined by ;
Ri=riAp13+At13  (6)
while the diffuseness parameter was defined by:
ai=0.734-150Zt2+500 (7)
where Ap(t) are the mass numbers of the projectile and target nuclei, and Zt is the atomic number of the target.
The introduced geometrical parameters were deduced by fitting the elastic scattering data using the double folding potential by minimising the χ2 value in the OM code. The best value of χ2 was defined by :
χ2=1Ni=1Nσcalθi-σexpθiσexpθi2(8)
where σcal(θi) and σexp(θi) are, respectively, the calculated and experimental values of the elastic scattering differential cross-section at θi and σexp(θi) is the corresponding experimental error. At the same time, N is the number of data points.
3. Results
The analyses of elastic scattering of d+Li 6 and d+Be 9 were performed using the parameterised M3Y-type interaction in the double-folding model framework. The strengths of the folded potentials were evaluated. The calculated reaction cross-sections were consistent with experimentally measured ones and those obtained using other theoretical methods . The deduced best-fit parameters of the double-folding calculations are presented in Table 1.
Table 1. Best-fit parameters deduced from the double folding calculations of elastic scattering of deuteron from Li 6 and Be 9.

Target

Elab (MeV)

Nr

Ni

σr (mb)

σtot (mb)

Li 6

25

1.50

0.72

825.97

1480.33

171

1.80

0.90

437.63

850.07

Be 9

15.8

1.20

0.50

960.99

1692.04

27.7

1.25

0.55

848.97

1564.81

The sensitivity of the strengths of the folded potential was carried out by varying Nr and Ni around best-fit values to the experimental data. The results showed that the differential cross-sections were more sensitive to Nr than the Ni. particularly, the variation of Ni values only impacted the magnitude of the absorption potential. The real renormalisation factors in Table 1 show that the strengths of real potentials were underestimated, hence the tuning of the renormalization factors to values greater than unity. On the other hand, the imaginary potentials had factors less than unity, suggesting their strengths were overestimated and thus required reduction. In conclusion, the derived folded potentials were found appropriate for the studies of nuclear reactions, as physical observables of the reactions were well reproduced.
Figure 1. Radial shape of the real and imaginary components of the double-folded optical potential of d+Li 6 elastic scattering at Elab=25 MeV.
Figure 2. Radial shape of the real and imaginary components of the double-folded optical potential of d+Li 6 elastic scattering at Elab=171 MeV.
Figure 3. Radial shape of the real and imaginary components of the double-folded optical potential of d+Li 6 elastic scattering at Elab=15.8 MeV.
Figure 4. Radial shape of the real and imaginary components of the double-folded optical potential of d+Li 6 elastic scattering at Elab=27.7 MeV.
The depths of the folded potentials were obtained, and the plots of the depths of the folded potentials to the radial distance (r) are given in Figures 1-4. The depths of the folded potentials assumed the Woods-Saxon form and were found to be attractive and short-ranged within short internuclear distances of 0r5.5 fm at all energies. The blue curves of Figures 1-4 represent the results of the real part of the folded potential, while the red curves denote the imaginary parts of the folded potentials. The real parts of the folded optical potentials were found to be deeper than the imaginary part at all incident energies. This observation is a manifestation of the larger Nr values that were needed to optimise the fit of the scattering data.
It was observed that the χ2 value obtained for the 27.7 MeV scattering data of the deuteron on Be 9 was exceptionally large, implying a poor fit quality. This large value of χ2 could likely be attributed to limitations in the OM at this energy or unaccounted contributions from other reaction mechanisms. The geometrical parameters of these interactions were derived, and the results are presented in Table 2. The extracted radii Rv(w) indicates that the nuclear surface extends slightly beyond the nominal strong absorption radius. This indicates that the elastic scattering of deuteron from Li 6, and Be 9 predominantly probes the surface region of Li 6, and Be 9. On the other hand, the larger values of aw implies a stronger surface absorption effect, which is consistent with significant coupling to non-elastic channels in these reactions.
Table 2. Best-fit geometrical parameters of the real and imaginary parts of the optical potential for d+Li 6 and d+Be 9 elastic scattering at different incident energies. χ² values reflect the quality of the fit between theoretical and experimental cross-sections.

Target

Elab (MeV)

Vr (MeV)

Rv (fm)

av (fm)

Wi (MeV)

Rw (fm)

aw (fm)

χ2

Li 6

25

66.14

0.87

0.76

31.41

0.75

0.81

16.17

171

50.49

0.65

0.75

16.63

0.78

1.11

2.97

Be 9

15.8

63.30

0.88

0.83

33.07

0.75

0.81

4.59

27.7

66.00

0.79

0.89

30.00

1.01

0.43

5756.92

The differential cross-sections of deuteron scattering from Li 6 and Be 9 were measured using the derived folded potential in the elastic channel. The plots of differential cross sections relative to the angles in the centre of mass are shown in Figures 5-8. The solid line in these figures represents the result of the theoretical calculations, while the solid dots correspond to the experimental data. The fits between the angular distributions of the theoretical calculations and the experimental data were well reproduced at all incident energies. However, small deviations were observed in the backward angles. The deviation observed between the theoretical predictions and experimental data at backward angles can be attributed to additional reaction mechanisms like breakup or nucleon transfer that were not accounted for by the present optical model. The observed minimum in the d+Li 6 scattering data at 25 MeV was not peculiar to this work; it was also observed when phenomenological potentials were used .
Figure 5. Angular distributions of d+Li 6 elastic scattering at Elab=25 MeV.
Figure 6. Angular distributions of d+Li 6 elastic scattering at Elab=171 MeV.
Figure 7. Angular distribution of d+Be 9 elastic scattering at Elab=15.8 MeV.
Figure 8. Angular distribution of d+Be 9 elastic scattering at Elab=27.7 MeV.
Figure 9. Modulus of the elastic S-matrix as a function of total orbital angular momentum of d+Li 6 at Elab=25 MeV.
Figure 10. Modulus of the elastic S-matrix as a function of total orbital angular momentum of d+Li 6 at Elab=171 MeV.
Figure 11. Modulus of the elastic S-matrix as a function of total orbital angular momentum of d+Be 9 at Elab=15.8 MeV.
Figure 12. Modulus of the elastic S-matrix as a function of total orbital angular momentum of d+Be 9 at Elab=27.7 MeV.
To analyse the absorption effect of the formulated nuclear potential, the moduli of the S-matrix were obtained. The plots of the moduli of the S-matrix elements to the angular momenta are shown in Figures 9-12. The plots of the moduli of SL revealed that the nuclear potential made a significant contribution to the interactions within small impact parameters between 0L10. Beyond this range, the magnitude of SL was found to be maximum, i.e., SL=1. In the case of the 171 MeV scattering data, the SL values ranged from 0.3SL1 in the angular region of 0L20. From the plot of the S-matrix element, it was further seen that absorption effects were present as seen in the range of values of L, for which SL1, however, no region of complete absorption was observed.
4. Conclusion
This study investigated the elastic scattering of deuterons from Li 6, and Be 9 using a double-folding optical model potential derived from the density-dependent M3Y-type interaction. The derived optical potentials successfully reproduced the measured angular distributions and reaction cross-sections across a range of incident energies. Renormalization factors indicated that the real parts of the potentials were generally underestimated, while the imaginary parts were overestimated—a trend consistent with theoretical expectations in light-ion scattering. The folded potentials exhibited Woods-Saxon-like radial behaviour, confirming their short-range, attractive nature. Additionally, the S-matrix analyses revealed realistic absorption behaviour at small impact parameters, with no dominant region of strong absorption. The overall agreement with experimental data validates the use of the M3Y-type interaction and supports its further application in modelling nuclear reaction studies. While the present optical model analysis reproduces the overall angular distributions reasonably well, its limitations must be acknowledged. The model does not explicitly account for coupling reaction mechanisms in other non-elastic channels, which likely contributes to the discrepancies at backward angles and the high χ² values for certain energy sets. Future studies will incorporate coupled-channel calculations to address these shortcomings.
Abbreviations

DFM

Double-Folding Model

HI

Heavy-Ion

M3Y

Michigan Three Yukawa

NRV

Nuclear Reaction Video

OM

Optical Model

Conflicts of Interest
The authors declare no conflicts of interest.
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    Abenga, R. C., Bijimi, G. A. (2025). Examining the Angular Distribution of Deuteron Scattering from 6Li and 9Be in the Elastic Channel. International Journal of Applied Mathematics and Theoretical Physics, 11(3), 36-43. https://doi.org/10.11648/j.ijamtp.20251103.11

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    Abenga, R. C.; Bijimi, G. A. Examining the Angular Distribution of Deuteron Scattering from 6Li and 9Be in the Elastic Channel. Int. J. Appl. Math. Theor. Phys. 2025, 11(3), 36-43. doi: 10.11648/j.ijamtp.20251103.11

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    Abenga RC, Bijimi GA. Examining the Angular Distribution of Deuteron Scattering from 6Li and 9Be in the Elastic Channel. Int J Appl Math Theor Phys. 2025;11(3):36-43. doi: 10.11648/j.ijamtp.20251103.11

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  • @article{10.11648/j.ijamtp.20251103.11,
      author = {Raymond Chivirter Abenga and Gertrude Ashia Bijimi},
      title = {Examining the Angular Distribution of Deuteron Scattering from 6Li and 9Be in the Elastic Channel},
      journal = {International Journal of Applied Mathematics and Theoretical Physics},
      volume = {11},
      number = {3},
      pages = {36-43},
      doi = {10.11648/j.ijamtp.20251103.11},
      url = {https://doi.org/10.11648/j.ijamtp.20251103.11},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijamtp.20251103.11},
      abstract = {The theoretical analyses of the elastic scattering of deuteron from 6Li, and 9Be were performed in the optical model (OM) framework. The double-folding model with a density-dependent M3Y-type effective interaction was used to derive both the real and the imaginary components of the optical potential. The derived nuclear optical potentials were subsequently employed in the OM formalism to analyse the angular distribution data of deuteron scattering from 6Li, and 9Be at different incident energies. The calculated differential cross-sections were compared with experimental data across multiple incident energies. The results demonstrate that the derived potentials accurately reproduce experimental observables, confirming the reliability of the double-folding model and the OM for modelling light-ion scattering. These findings also underscore the applicability of the M3Y-type interaction in describing short-range nuclear interactions in light nuclei.},
     year = {2025}
    }
    

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  • TY  - JOUR
    T1  - Examining the Angular Distribution of Deuteron Scattering from 6Li and 9Be in the Elastic Channel
    AU  - Raymond Chivirter Abenga
    AU  - Gertrude Ashia Bijimi
    Y1  - 2025/08/07
    PY  - 2025
    N1  - https://doi.org/10.11648/j.ijamtp.20251103.11
    DO  - 10.11648/j.ijamtp.20251103.11
    T2  - International Journal of Applied Mathematics and Theoretical Physics
    JF  - International Journal of Applied Mathematics and Theoretical Physics
    JO  - International Journal of Applied Mathematics and Theoretical Physics
    SP  - 36
    EP  - 43
    PB  - Science Publishing Group
    SN  - 2575-5927
    UR  - https://doi.org/10.11648/j.ijamtp.20251103.11
    AB  - The theoretical analyses of the elastic scattering of deuteron from 6Li, and 9Be were performed in the optical model (OM) framework. The double-folding model with a density-dependent M3Y-type effective interaction was used to derive both the real and the imaginary components of the optical potential. The derived nuclear optical potentials were subsequently employed in the OM formalism to analyse the angular distribution data of deuteron scattering from 6Li, and 9Be at different incident energies. The calculated differential cross-sections were compared with experimental data across multiple incident energies. The results demonstrate that the derived potentials accurately reproduce experimental observables, confirming the reliability of the double-folding model and the OM for modelling light-ion scattering. These findings also underscore the applicability of the M3Y-type interaction in describing short-range nuclear interactions in light nuclei.
    VL  - 11
    IS  - 3
    ER  - 

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