Calculation of electron-impact ionization cross sections: Bottom-up inductive vs. top-down deductive approaches

Abstract. We report electron impact ionisation cross sections (EICSs) of iron oxide molecules, FexOx and FexOx+1 with x = 1, 2, 3, from the ionisation threshold to 10 keV, obtained with the Deutsch-Märk (DM) and binary-encounter-Bethe (BEB) methods. The maxima of the EICSs range from 3.10 to 9.96 × 10 −16 cm 2 located at 59-72 eV and 5.06 to 14.32 × 10 −16 cm 2 located at 85-108 eV for the DM and BEB approaches, respectively. The orbital and kinetic energies required for the BEB method are obtained by employing effective core potentials for the inner core electrons in the quantum chemical calculations. The BEB cross sections are 1.4-1.7 times larger than the DM cross sections which can be related to the decreasing population of the Fe 4s orbitals upon addition of oxygen atoms, together with the different methodological foundations of the two methods. Both the DM and BEB cross sections can be fitted excellently to a simple analytical expression used in modelling and simulation codes employed in the framework of nuclear fusion research.

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“…nl (u) becomes a constant ensuring the high-energy dependence of the cross sections predicted by the Born-Bethe theory [45,46].…”

Section: The Dm Formalismmentioning

confidence: 99%

Electron impact ionisation cross sections of iron oxides

et al. 2017

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“…The efficiency of dissociative electron attachment as a function of electron energy was simulated by resonance theory for a few molecules, e.g., HBr [ 41 ], isocyanic acid HNCO [ 42 ], methylformate HCOOCH 3 [ 43 ], and acetylene C 2 H 2 [ 44 ]. The efficiency of dissociative ionization has been modeled by the quasi-equilibrium theory for dimethyl silane (CH 3 ) 2 SiH 2 [ 45 ] by binary encounter Bethe formalism for small polyatomic atmospheric gases and hydrocarbons [ 46 ], or using the Deutsch-Märk (DM) formalism for noble gases [ 47 ]. Experimental approaches to explore the fragmentation behavior mechanisms of metalorganic molecules include ultra-high vacuum (UHV) gas phase [ 12 , 13 , 48 , 49 ] or condensed-phase investigations at cryogenic UHV conditions [ 50 , 51 , 52 , 53 , 54 ].…”

Section: Introductionmentioning

confidence: 99%

In Situ Time-of-Flight Mass Spectrometry of Ionic Fragments Induced by Focused Electron Beam Irradiation: Investigation of Electron Driven Surface Chemistry inside an SEM under High Vacuum

et al. 2022

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Recent developments in nanoprinting using focused electron beams have created a need to develop analysis methods for the products of electron-induced fragmentation of different metalorganic compounds. The original approach used here is termed focused-electron-beam-induced mass spectrometry (FEBiMS). FEBiMS enables the investigation of the fragmentation of electron-sensitive materials during irradiation within the typical primary electron beam energy range of a scanning electron microscope (0.5 to 30 keV) and high vacuum range. The method combines a typical scanning electron microscope with an ion-extractor-coupled mass spectrometer setup collecting the charged fragments generated by the focused electron beam when impinging on the substrate material. The FEBiMS of fragments obtained during 10 keV electron irradiation of grains of silver and copper carboxylates and shows that the carboxylate ligand dissociates into many smaller volatile fragments. Furthermore, in situ FEBiMS was performed on carbonyls of ruthenium (solid) and during electron-beam-induced deposition, using tungsten carbonyl (inserted via a gas injection system). Loss of carbonyl ligands was identified as the main channel of dissociation for electron irradiation of these carbonyl compounds. The presented results clearly indicate that FEBiMS analysis can be expanded to organic, inorganic, and metal organic materials used in resist lithography, ice (cryo-)lithography, and focused-electron-beam-induced deposition and becomes, thus, a valuable versatile analysis tool to study both fundamental and process parameters in these nanotechnology fields.

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“…where a 0 is the Bohr radius of 5.29x10 -11 m, u=E e /E i , and A, B and C are Bethe coefficients for hydrogen equal to 0.2834, 1.2566 and -2.63 respectively [8]. This yields σ TICS of 7.94x10 -19 and 1.24 x10 -19 cm 2 for 20 and 150 keV respectively.…”

Section: Charge Breeder Specificationmentioning

confidence: 98%

High performance charge breeder for HIE-ISOLDE and TSR@ISOLDE applications

Shornikov¹,

Beebe²,

Mertzig³

et al. 2015

AIP Conference Proceedings

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Abstract. We report on the development of the HEC 2 (High Energy Compression and Current) charge breeder, a possible high performance successor to REXEBIS at ISOLDE. The new breeder would match the performance of the HIE-ISOLDE linac upgrade and make full use of the possible installation of a storage ring at ISOLDE (the TSR@ISOLDE initiative [1]). Dictated by ion beam acceptance and capacity requirements, the breeder features a 2-3.5 A electron beam. In many cases very high charge states, including bare ions up to Z=70 and Li/Na-like up to Z=92 could be requested for experiments in the storage ring, therefore, electron beam energies up to 150 keV are required. The electron-beam current density needed for producing ions with such high charge states at an injection rate into TSR of 0.5-1 Hz is between 10 and 20 kA/cm 2 , which agrees with the current density needed to produce A/q<4.5 ions for the HIE-ISOLDE linac with a maximum repetition rate of 100 Hz. The first operation of a prototype electron gun with a pulsed electron beam of 1.5 A and 30 keV was demonstrated in a joint experiment with BNL [2]. In addition, we report on further development aiming to achieve CW operation of an electron beam having a geometrical transverse ion-acceptance matching the injection of 1 + ions (11.5 μm), and an emittance/energy spread of the extracted ion beam matching the downstream mass separator and RFQ (0.08 μm normalized / ± 1% ). HIE-ISOLDE FACILITY OVERVIEWAfter more than 20 years of successful operation of ISOLDE at the PS Booster, CERN's radioactive ion beam (RIB) facility is undergoing another major upgrade. The improvement program, called HIE-ISOLDE (where HIE stands for High Intensity and Energy), includes the study of an intensity upgrade of the radioactive ion production stage, beam quality improvement and construction of a higher energy superconducting postaccelerating linac. An overview of the ongoing program has been given in ref. [3]. Part of the beam quality improvement concerns the charge breeder, which should ideally suit the new superconducting linac and provide a beam with improved time structure to the users.An independent parallel proposal related to post-accelerated RIBs at ISOLDE is the relocation of the Test Storage Ring (TSR) from MPIK (Heidelberg, Germany) to ISOLDE [1]. This project would enable a wide range of new experiments, thanks to a unique combination of an ISOL-facility and a heavy ion storage ring. The interfacing of TSR and the HIE-ISOLDE linac will put several stringent constraints on the RIB injection system and in particular on the charge breeder.At ISOLDE the radioactive ions are produced continuously at the target-ion-sources. Extracted ions are magnetically mass separated and injected into a Penning-type ion trap called REXTRAP. The ion beam is accumulated in the trap and the beam is cooled using buffer-gas and RF excitation schemes [4]. The minimum cooling time is 20 ms, but in case a longer breeding time is required, or the injection rate into TSR is lower, the

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Calculation of electron-impact ionization cross sections: Bottom-up inductive vs. top-down deductive approaches

Cited by 5 publications

References 65 publications

Electron impact ionisation cross sections of iron oxides

Electron impact ionisation cross sections of iron oxides

In Situ Time-of-Flight Mass Spectrometry of Ionic Fragments Induced by Focused Electron Beam Irradiation: Investigation of Electron Driven Surface Chemistry inside an SEM under High Vacuum

High performance charge breeder for HIE-ISOLDE and TSR@ISOLDE applications

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