# Positron Scattering from Pyrimidine

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## Abstract

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## 1. Introduction

## 2. The Single-Centre Expansion Method and the Binary-Encounter-Bethe Model

#### 2.1. Elastic Cross-Sections

#### 2.2. Direct Ionisation Cross-Sections

## 3. Computational Details

## 4. Results

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Abbreviations

SCE | Single-Centre Expansion |

ECS | Elastic Cross-Sections |

DCS | Differential Cross-Sections |

TCS | Total Cross-Sections |

TICS | Total Ionisation Cross-Sections |

IE | Ionisation Energy |

BEB | Binary–Encounter–Bethe |

HF | Hartree–Fock |

DFT | Density Functional Theory |

IE | Ionisation Energy |

CC | Close-Coupling |

eV | Electron Volt |

au | Atomic Unit |

IAM | Independent Atom Approximation |

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**Figure 1.**DCS at different energies: circles, folded DCS of Palihawadana et al. [44]; line curve, Born-corrected DCS (this work); dashed dotted curve, Born cross-sections; open squares with dotted dashed curve, Sanz et al. with dipole potential [29]; dashed curve, Sanz et al. with dipole and quadrupole potentials [29]; dashed curve with cross, DCS results without Born correction; double dotted dashed curve, unfolded DCS of Barbosa et al. [12]. Their folded DCS are shown as a double dotted dashed curve with plus symbol.

**Figure 2.**ECS: (

**a**) Born-uncorrected; (

**b**) Born-corrected. Experimental results are denoted by symbols and the theoretical results by line curves or line curves with symbols. The notation “R-matrix, SP” in (

**b**) stands for “static-polarisation model”. “CC” model means the ground state and excited states included in the total wave function [29,30,43,44,45].

**Figure 3.**BEB ionisation cross-sections. The comparison is made with inelastic cross-sections (excitation plus ionisation) reported by Palihawadana et al. [44] and ionisation cross-sections due to electron impact. Squares: direct measurements of inelastic cross-sections (excitation plus ionisation) by Palihawadana et al. [44] denoted as A; stars: inelastic cross-sections as a difference of grand total and Ps and elastic cross-sections from Palihawadana et al. [44] denoted as B; line curve: BEB for positron (this work); dashed curve, inelastic cross-sections (excitation plus ionisation) due to positron impact of Singh et al. [30]; dotted dashed curve, positron impact total inelastic cross-sections of Sanz et al. [29]; double dotted dashed curve, electron ionisation of Bug et al. [76].

**Figure 4.**TCS: line curve, this work (sum of ECS+Ps+BEB); dashed curves, this work (sum of ECS+BEB); dashed dotted curve, Sanz et al. [29]; dotted dashed curve, Singh et al. [30]; diamonds, uncorrected TCS of Zecca et al. [43]; circles, uncorrected results of Palihawadana et al. [44]; squares, recommended data of Brunger et al. [45]; triangles, forward-angle-corrected TCS of Palihawadana et al. [44].

**Table 1.**Experimental values of a few important target parameters of pyrimidine. The SCE value of the dipole moment is also shown.

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**MDPI and ACS Style**

Prashant, A.; Luthra, M.; Goswami, K.; Bharadvaja, A.; Baluja, K.L.
Positron Scattering from Pyrimidine. *Atoms* **2023**, *11*, 55.
https://doi.org/10.3390/atoms11030055

**AMA Style**

Prashant A, Luthra M, Goswami K, Bharadvaja A, Baluja KL.
Positron Scattering from Pyrimidine. *Atoms*. 2023; 11(3):55.
https://doi.org/10.3390/atoms11030055

**Chicago/Turabian Style**

Prashant, Abhishek, Meetu Luthra, Kanupriya Goswami, Anand Bharadvaja, and Kasturi Lal Baluja.
2023. "Positron Scattering from Pyrimidine" *Atoms* 11, no. 3: 55.
https://doi.org/10.3390/atoms11030055