1 Introduction 2 Experimental methods 3 Theoretical methods 4 The H2+molecule 5 Diatomic hydride ions 6 Diatomic ions 7 The H3+ molecule 8 Polyatomic ions 9 Related processes 10 Applications

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Dissociative Recombination of Molecular Ions

Author(s): Bartoszek, L; et al. | Abstract: The Mu2e experiment at Fermilab will search for charged lepton flavor violation via the coherent conversion process mu- N --g e- N with a sensitivity approximately four orders of magnitude better than the current world's best limits for this process. The experiment's sensitivity offers discovery potential over a wide array of new physics models and probes mass scales well beyond the reach of the LHC. We describe herein the preliminary design of the proposed Mu2e experiment. This document was created in partial fulfillment of the requirements necessary to obtain DOE CD-2 approval.

Mu2e Technical Design Report

We review the gas-phase chemistry in extraterrestrial space that is driven by reactions with atomic and molecular ions. Ions are ubiquitous in space and are potentially responsible for the formation of increasingly complex interstellar molecules. Until recently, positively charged atoms and molecules were the only ions known in space; however, this situation has changed with the discovery of various molecular anions. This review covers not only the observation, distribution and reactions of ions in space, but also laboratory-based experimental and theoretical methods for studying these ions. Recent results from space-based instruments, such as those on the Cassini-Huygens space mission and the Herschel Space Observatory, are highlighted.

https://iopscience.iop.org/article/10.1088/0034-4885/75/6/066901/pdf

Ion chemistry in space

Atomic negative ions: structure, dynamics and collisions

A beam extraction method using a transverse rf electric field with amplitude and frequency modulation has been studied in order to develop an irradiation method which is synchronized with the breathing of a patient for high-quality charged particle therapy. The dependence of the extracted beam intensity on the voltage, the frequency band width and the center frequency of the transverse rf electric field has been investigated. The extracted beam intensity was slightly increased from that of the ordinary slow extraction method with a third order resonance. The response of the extracted beam intensity to the applied transverse rf electric field was as prompt as within 1 ms. The horizontal emittance of beams extracted by the present method was reduced by about 70% compared with that by the ordinary one due to utilizing a constant separatrix. Amplitude modulation can control the global beam spill structure. The frequency modulation reduced the effect of the current ripple of the main quadrupole magnets.

Slow beam extraction by a transverse RF field with AM and FM

Dissociative recombination of ${\mathrm{HeH}}^{+}$ has been studied for the ${\mathrm{HeH}}^{+}$ ion stored in a storage ring. A strong recombination resonance having a peak at around 20 eV center-of-mass energy has been found for the first time in addition to the known recombination at around 0 eV center-of-mass energy. The strength of the recombination rate changes depending on the storage time of ${\mathrm{HeH}}^{+}$ ions.

Dissociative recombination of HeH+ at large center-of-mass energies.

A slow beam extraction system using the third order resonance has been constructed at TARN II and beam extraction tests have been performed. By the ordinary scheme where the tune is shifted to the resonance with ramping the excitation strength of the lattice quadrupole magnets, an extraction efficiency of 90% is attained. A new scheme increasing the horizontal emittance of the circulating beam is applied to extract the beam. A very long beam spill of 800 s is obtained by this scheme. A method using a transverse rf field is also studied experimentally, resulting in an extracted beam with smaller emittance.

Slow beam extraction at TARN II

Dissociative recombination of ${\mathrm{HD}}^{+}$ was studied with an adiabatically expanded low-temperature electron beam in a cooler ring TARN II. Measurements were performed over a wide energy range from 0 to 40 eV in the center of mass system. The spectrum at low electron energies less than 1 eV clearly shows structures even in the energy region of the order of 1 meV. The results agree well with the theoretical calculations based on a multichannel quantum defect theory including rotational motions and off-the-energy-shell effects.

Dissociative Recombination of HD + with an Ultracold Electron Beam in a Cooler Ring

LETTER TO THE EDITOR: Dissociative recombination of ? isotopes with an ultra-cold electron beam from a superconducting electron cooler in a storage ring

Y. Arakaki

Papers

Dissociative recombination of HeH+ at large center-of-mass energies.

Slow beam extraction at TARN II

Dissociative Recombination of HD + with an Ultracold Electron Beam in a Cooler Ring

LETTER TO THE EDITOR: Dissociative recombination of ? isotopes with an ultra-cold electron beam from a superconducting electron cooler in a storage ring

Evidence of Superelastic Electron Collisions from H 2 + Studied by Dissociative Recombination Using an Ultracold Electron Beam from a Cooler Ring