Applied Chemical Engineering

Simulation of Positron Lifetime Spectra in Aluminium: Influence of Time Response Function and Detector Configuration

Duaa Hatif Mohammed

University of Babylon, Department of Physics, Iraq

Mohanad Hussein Oleiwi

University of Babylon, Department of Physics, Iraq

DOI: https://doi.org/10.59429/ace.v9i2.5895

Keywords: Positron, Lifetime spectrum, Annihilation, Time response function

---

Abstract

This study investigates the influence of various factors on the quality and analysis of positron lifetime spectra. Theoretical simulations were performed to examine how these factors affect the quality and analysis of the positron annihilation spectrum. An aluminium (Al) sample was used to assess the spectra quality. The factors studied in this simulation were: the thickness of the material, the gap between the sample and detectors, and the angle between the two detectors. The thickness of the material was varied as 0.5,1, 1.5, 2, 2.5, 3, 3.5 and 4 mm, and the gap was varied as: 1, 2, 3,4,5,6,7 and 8 n air, and the angle was varied as:180o,190o,200o and 210o. The positron annihilation spectra were analyzed using the PEPEPOSFIT program to obtain the values of the lifetime components and the resolution function (FWHM).

It was observed that as the thickness of the sample material and the gap between the sample-source sandwich and detectors increases, the spectra become distorted. Furthermore, with an increase in the angle between the two detectors, the spectra become highly distorted. The setup with two detectors in a collinear (180°) geometry yielded the optimal spectrum. The spectra deviated from this optimal shape as the angle increased. At an angle of 210°, the spectrum was completely distorted, where three peaks appeared. This is attributed to the effect of the non-collinearity function on the integrity of the positron lifetime spectrum.

---

References

[1]. A. W. Dong, C. Pascual-Izarra, S. J. Pas, A. J. Hill, B. J. Boyd, and C. J. Drummond, “Positron Annihilation Lifetime Spectroscopy (PALS) as a Characterization Technique for Nanostructured Self-Assembled Amphiphile Systems,” The Journal of Physical Chemistry B, vol. 113, no. 1, pp. 84–91, Jan. 2009, doi: 10.1021/jp805280r.

[2]. S. M. Nuri, S. R. Hasan, and H. A. Mohammed, “The Thermal Effect on PLA And PLA/Curcumin Composite Properties under Positron Annihilation Lifetime Spectroscopy,” Iraqi Journal of Science, pp. 3407–3416, 2021.

[3]. S. M. Nuri, N. M. Hassan, and R. S. Bagelany, “AP01015 Extracting the Free Volume and Hole Fraction of Based Polymers under Positron Annihilation Lifetime Spectroscopy Technique,” Iraqi Journal of Applied Physics, vol. 21, no. 4, pp. 503–507, 2025, doi: 10.2025/sacjhr73.

[4]. D. Boras, D. Petschke, and T. Staab, “Geant4-based technical simulation study of plastic scintillators for Positron Annihilation Lifetime Spectroscopy (PALS),” Journal of Instrumentation, vol. 20, no. 01, p. T01009, 2025, doi: 10.1088/1748-0221/20/01/T01009.

[5]. M. H. Oleiwi and T. M. Talib, “Study positron lifetime spectrum with high resolution effect and lifetime effects,” Int. J. Appl. Eng. Res, vol. 12, p. 14854, 2017.

[6]. M. Elias, A. Al-Mashhadani, and Z. Al-Shiebani, “Temperature dependence of microstructure of biological tissues probed via the positronium method,” Dirasat: Pure Sciences, vol. 28, 2001.

[7]. R. Helm, J. Lehtonen, M. Mayerhofer, J. Mitteneder, W. Egger, R. Verbeke, P. Sperr, G. Dollinger, and M. Dickmann, “Positron-annihilation lifetime spectroscopy with in-situ control of temperature, pressure and atmosphere to determine the free-volume of soft materials,” Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, vol. 549, p. 165263, 2024, doi: https://doi.org/10.1016/j.nimb.2024.165263.

[8]. C. Fong, A. W. Dong, A. J. Hill, B. J. Boyd, and C. J. Drummond, “Positron annihilation lifetime spectroscopy (PALS): a probe for molecular organisation in self-assembled biomimetic systems,” Physical Chemistry Chemical Physics, vol. 17, no. 27, pp. 17527–17540, 2015, doi: 10.1039/C5CP01921D.

[9]. D. J. Keeble, S. Singh, R. A. Mackie, M. Morozov, S. McGuire, and D. Damjanovic, “Cation vacancies in ferroelectric pb TiO3 and Pb (Zr,Ti) O3: A positron annihilation lifetime spectroscopy study,” Physical Review B, vol. 76, no. 14, p. 144109, Oct. 2007, doi: 10.1103/PhysRevB.76.144109.

[10]. H. F. M. Mohamed, “Positron annihilation techniques as probes for investigation of the polymer electrolyte membranes with different ion exchange capacities,” Journal of the Egyptian Society for Basic Sciences-Physics, vol. 1, no. 2, pp. 66–82, 2024.

[11]. W. Brandt and R. Paulin, “Positron implantation-profile effects in solids,” Physical Review B, vol. 15, no. 5, pp. 2511–2518, Mar. 1977, doi: 10.1103/PhysRevB.15.2511.

[12]. G. Dlubek, C. Hübner, and S. Eichler, “Do MELT or CONTIN Programs Accurately Reveal the o-Ps Lifetime Distribution in Polymers?,” physica status solidi (a), vol. 172, no. 2, pp. 303–315, Apr. 1999, doi: 10.1002/(SICI)1521-396X(199904)172:2<303::AID-PSSA303>3.0.CO;2-C.

[13]. M. M. Shokoya, B.-M. Benkő, K. Süvegh, R. Zelkó, and I. Sebe, “Positron Annihilation Lifetime Spectroscopy as a Special Technique for the Solid-State Characterization of Pharmaceutical Excipients, Drug Delivery Systems, and Medical Devices—A Systematic Review,” 2023. doi: 10.3390/ph16020252.

[14]. H. Sormann, P. Kindl, and W. Puff, “Investigations on the reliability of a multi-component analysis of positron lifetime spectra, using a new method of producing computer-simulated test spectra,” Nuclear Instruments and Methods in Physics Research, vol. 206, no. 1–2, pp. 203–209, 1983.

[15]. W. Puff, “PFPOSFIT: A new version of a program for analysing positron lifetime spectra with non-gaussian prompt curve,” Comput. Phys. Commun.;(Netherlands), vol. 30, no. 4, 1983.