# Differential Studies of Argon Particle and Antiparticle Interactions: Present Status and Future Possibilities

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## Abstract

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## 1. Introduction

_{o}) greater than 2 a.u., in order to avoid electron capture, positronium formation, and electron exchange processes. The overall message from these comparisons is to show where future studies on the single and double differential level might provide useful information for testing theoretical predictions regarding how simply changing the sign of the projectile charge or the projectile mass alters the inelastic cross-section.

## 2. Theory

_{max}, ${N}_{t}$is the number of trajectories that satisfy the criteria for ionization, and ${b}_{i}$ is the actual impact parameter for the trajectory corresponding to the ionization process under consideration in the energy interval ΔE and the emission angle interval ΔΩ of the electron.

## 3. Antiparticle and Particle Impact Comparisons

#### 3.1. Total Cross-Sections (TCS)

#### 3.2. Single Differential Cross-Sections (SDCS)

_{post}, with respect to the impact velocity, v

_{p}, is used. Thus, for leptons, the maximum-scaled velocity is 1 and for protons, there is a rapid decrease in the cross-sections beginning at a scaled velocity of 2, i.e., the value obtained classically for elastic collisions between a massive projectile and a light target.

#### 3.3. Double Differential Cross-Sections (DDCS)

## 4. Summary and Possible Future Investigations

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**Bethe scaled single differential cross-section energy distributions for 100, 250, and 500 eV electron (blue circles) [20,21], positron (green triangles, scaled; see text) [23] (0.2 Crooks and Rudd, ref. [22]; 0.5 Gabler et al., ref. [22]; 1.0 MeV Toburen; ref. [22]), and proton impacts (red symbols); and our CTMC results for 500 eV electron and positron impacts (blue and green lines, respectively). Individual curves are shown for the ejected electrons and the scattered projectile CTMC results.

**Figure 2.**Single differential cross-section angular distributions for 100, 250, and 500 eV electron impacts (half-filled blue circles) [20,21]; 120 eV positron impact (open and filled green circles, scaled; see text) [25] (0.2 Crooks and Rudd, ref. [22]; 0.5 Gabler et al., ref. [22]; 1.0 MeV Toburen, ref. [22]) and proton impact (red symbols); and our CTMC results for 500 eV electron and positron impact (blue and green lines, respectively). The solid curves are the ejected electrons and the dashed curves the scattered projectile contributions. The intermediate and high energy data are divided by 10 and 100, respectively, for display purposes.

**Figure 3.**Double differential cross-sections for 100 eV electrons (half-filled blue circles) [20,21] and positrons (open red circles and stars) [27]; 0.2 MeV protons (red x) (Crooks and Rudd, ref. [22]); and our CTMC results for electron and positron impact (blue and red lines, respectively). The solid curves are for the ejected electrons and the dashed curves for the scattered projectile contributions.

**Figure 5.**Double differential cross-sections for 15 eV electron emission from argon resulting from 100 eV electron (blue-filled circles [20] and open triangles [29]), positron (green-filled triangles [29] and open stars [27]), and 200 keV proton [22] impact (red cross). The positron data of Schmitt et al. [29] were adjusted in magnitude and shape. See text for details.

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**MDPI and ACS Style**

DuBois, R.D.; Tőkési, K.
Differential Studies of Argon Particle and Antiparticle Interactions: Present Status and Future Possibilities. *Atoms* **2023**, *11*, 151.
https://doi.org/10.3390/atoms11120151

**AMA Style**

DuBois RD, Tőkési K.
Differential Studies of Argon Particle and Antiparticle Interactions: Present Status and Future Possibilities. *Atoms*. 2023; 11(12):151.
https://doi.org/10.3390/atoms11120151

**Chicago/Turabian Style**

DuBois, Robert D., and Károly Tőkési.
2023. "Differential Studies of Argon Particle and Antiparticle Interactions: Present Status and Future Possibilities" *Atoms* 11, no. 12: 151.
https://doi.org/10.3390/atoms11120151