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14 pages, 2339 KB

Open AccessArticle

Experimental and Theoretical Studies of Dissociative Electron Attachment to Metabolites Oxaloacetic and Citric Acids

by Janina Kopyra, Paulina Wierzbicka, Adrian Tulwin, Guillaume Thiam, Ilko Bald, Franck Rabilloud and Hassan Abdoul-Carime

Int. J. Mol. Sci. 2021, 22(14), 7676; https://doi.org/10.3390/ijms22147676 - 18 Jul 2021

Cited by 6 | Viewed by 3499

Abstract

In this contribution the dissociative electron attachment to metabolites found in aerobic organisms, namely oxaloacetic and citric acids, was studied both experimentally by means of a crossed-beam setup and theoretically through density functional theory calculations. Prominent negative ion resonances from both compounds are observed peaking below 0.5 eV resulting in intense formation of fragment anions associated with a decomposition of the carboxyl groups. In addition, resonances at higher energies (3–9 eV) are observed exclusively from the decomposition of the oxaloacetic acid. These fragments are generated with considerably smaller intensities. The striking findings of our calculations indicate the different mechanism by which the near 0 eV electron is trapped by the precursor molecule to form the transitory negative ion prior to dissociation. For the oxaloacetic acid, the transitory anion arises from the capture of the electron directly into some valence states, while, for the citric acid, dipole- or multipole-bound states mediate the transition into the valence states. What is also of high importance is that both compounds while undergoing DEA reactions generate highly reactive neutral species that can lead to severe cell damage in a biological environment. Full article

(This article belongs to the Special Issue Electron and Photon Interactions with Bio(Related) Molecules)

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14 pages, 1057 KB

Open AccessArticle

Analysis of Multipolar Linear Paul Traps for Ion–Atom Ultracold Collision Experiments

by M. Niranjan, Anand Prakash and S. A. Rangwala

Atoms 2021, 9(3), 38; https://doi.org/10.3390/atoms9030038 - 29 Jun 2021

Cited by 9 | Viewed by 4320

Abstract

We evaluate the performance of multipole, linear Paul traps for the purpose of studying cold ion–atom collisions. A combination of numerical simulations and analysis based on the virial theorem is used to draw conclusions on the differences that result, by considering the trapping details of several multipole trap types. Starting with an analysis of how a low energy collision takes place between a fully compensated, ultracold trapped ion and an stationary atom, we show that a higher order multipole trap is, in principle, advantageous in terms of collisional heating. The virial analysis of multipole traps then follows, along with the computation of trapped ion trajectories in the quadrupole, hexapole, octopole and do-decapole radio frequency traps. A detailed analysis of the motion of trapped ions as a function of the amplitude, phase and stability of the ion’s motion is used to evaluate the experimental prospects for such traps. The present analysis has the virtue of providing definitive answers for the merits of the various configurations, using first principles. Full article

(This article belongs to the Special Issue Low Energy Interactions between Ions and Ultracold Alkali Atoms)

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17 pages, 4070 KB

Open AccessArticle

Thermometry in a Multipole Ion Trap

by Markus Nötzold, Saba Zia Hassan, Jonas Tauch, Eric Endres, Roland Wester and Matthias Weidemüller

Appl. Sci. 2020, 10(15), 5264; https://doi.org/10.3390/app10155264 - 30 Jul 2020

Cited by 22 | Viewed by 5999

Abstract

We present a characterization of the ions’ translational energy distribution in a multipole ion trap. A linear mapping between the energy distribution of the trapped ions onto the ions’ time-of-flight (TOF) to a detector is demonstrated. For low ion temperatures, a deviation from linearity is observed and can be attributed to the emergence of multiple potential minima. The potential landscape of the trapped ions is modeled via the finite element method, also accounting for subtleties such as surface-charge accumulation. We demonstrate the validity of our thermometry method by simulating the energy distribution of the ion ensemble thermalized with buffer gas using a Molecular Dynamics (MD) simulation. A comparison between the energy distribution of trapped ions in different multipole trap configurations—i.e., with hyperbolic rods, cylindrical rods, and cylindrical wires—is provided. With these findings, one can map the temperature of the trapped ions down to the Kelvin regime using their TOF distributions. This enables future studies on sympathetic cooling and chemical reactions involving ions in multipole traps. Full article

(This article belongs to the Special Issue Optical Trapping of Ions and Atoms 2020: Novel Advances and Prospects)

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10 pages, 4421 KB

Open AccessArticle

Particle-in-Cell Simulation of Quasi-Neutral Plasma Trapping by RF Multipole Electric Fields

by Nathaniel K. Hicks, Amanda Bowman and Katarina Godden

Physics 2019, 1(3), 392-401; https://doi.org/10.3390/physics1030028 - 3 Dec 2019

Cited by 4 | Viewed by 5009

Abstract

Radio-frequency (RF) charged particle traps, such as the Paul trap or higher order RF multipole traps, may be used to trap quasi-neutral plasma. The presence of positive and negative plasma species mitigates the ejection of particles that occurs due to space charge repulsion. For symmetric species, such as a pair plasma, the trapped particle distribution is essentially equal for both species. For plasma with species of disparate charge-to-mass ratio, the RF parameters are chosen to directly trap the lighter species, leading to loss of the heavier species until sufficient net space charge develops to prevent further loss. Two-dimensional (2D) electrostatic particle-in-cell simulations are performed of cases with mass ratio m₊/m₋ = 10, and also with ion–electron plasma. Multipole cases including order N = 2 (quadrupole) and higher order N = 8 (hexadecapole) are considered. The light ion-heavy ion N = 8 case exhibits particles losses less than 5% over 2500 RF periods, but the N = 8 ion–electron case exhibits a higher loss rate, likely due to non-adiabaticity of electron trajectories at the boundary, but still with low total electron loss current on the order of 10 μA. The N = 2 ion-electron case is adiabatic and stable, but is subject to a smaller trapping volume and greater initial perturbation of the bulk plasma by the trapping field. Full article

(This article belongs to the Section Applied Physics)

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