MULTIPLE IONIZATION OF THE RARE GASES BY SUCCESSIVE ELECTRON IMPACTS (0–250 eV): I. APPEARANCE POTENTIALS AND METASTABLE ION FORMATION

1967 ◽  
Vol 45 (5) ◽  
pp. 1791-1812 ◽  
Author(s):  
P. A. Redhead
Keyword(s):  
Electron Emission ◽  
Ion Source ◽  
Metastable States ◽  
Rare Gases ◽  
Trapped Ion ◽  
Sharp Maximum ◽  
Multiple Ionization ◽  
Metastable Ions ◽  
Charge Multiplicity ◽  
Charged Ions

Multiple ionization of the rare gases has been examined in a mass spectrometer with a trapped-ion source. Ions with charge multiplicity up to n = 2 (He), n = 5 (Ne), n = 6 (Ar), n = 7 (Kr), and n = 10 (Xe) were observed with electron energies less than 250 eV. For He and Ne the thresholds agree with spectroscopic values of the ionization potentials, indicating a process of the form eN/ee(N + 1), where N represents an ion of charge multiplicity n. For Ar, Kr, and Xe, processes involving metastable states of the ion are also observed, eN/eNm; eNm/ee(N + 1). The estimated energies of the metastable levels of Ar+, Kr+, Xe+, Ar2+, and Xe2+ are in agreement with spectroscopic values. The energies of the metastable states of Ar+, Kr+, and Xe+ are in agreement with measurements of Auger electron emission from metals by metastable ions. The metastable levels estimated for the more highly charged ions (up to n = 5 for Ar, n = 6 for Kr, and n = 8 for Xe) have not been observed previously. The excitation functions of the metastable levels of Ar+, Kr+, and Xe+ are very similar and show a very sharp maximum near threshold.

Sequential Impact Mass Spectrometry: Estimates of Metastable Ion Cross Sections

1971 ◽  
Vol 49 (24) ◽  
pp. 3059-3063 ◽  
Author(s):  
P. A. Redhead
Keyword(s):  
Experimental Data ◽  
Mass Spectrometry ◽  
Cross Sections ◽  
Ion Source ◽  
Metastable States ◽  
Ionization Cross ◽  
Trapped Ion ◽  
Charge Multiplicity ◽  
Ionization Cross Sections ◽  
Impact Mass

A trapped-ion source has been developed in which ions can undergo as many as 12 consecutive collisions with electrons; ions leaking out of the trap are analyzed with a mass spectrometer. When long-lived metastable states of the ions exist, the collision sequence may involve metastable states of the ions, e.g.[Formula: see text]where Xn represents an ion of charge multiplicity n, and Xn* represents a metastable ion. In a previous paper an approximate method was developed to estimate ionization cross sections for the case where the collision sequence involved only the ground states of the ions. The present paper extends this model to the case where metastable states are involved, and permits rough estimates of cross sections for excitation to and from the metastable states. The method is applied to experimental data for argon in the electron energy range of 40 to 100 eV.

Multiple ionization of mercury by successive electron impacts

1968 ◽  
Vol 46 (17) ◽  
pp. 1905-1913 ◽  
Author(s):  
P. A. Redhead ◽  
S. Feser
Keyword(s):  
High Current Density ◽  
Ionization Probability ◽  
Ion Current ◽  
High Current ◽  
Mercury Ions ◽  
Multiply Charged ◽  
Multiple Ionization ◽  
Charge Multiplicity ◽  
Slow Electrons ◽  
Charged Ions

Mercury ions of charge multiplicity up to n = 9 have been formed by repeated collisions of slow electrons (less than 150 eV) with ions trapped in an electron beam of high current density (~5 × 10−2 A cm−2). Ion current is observed at electron energies below the ionization potential for all multiply charged ions up to n = 8 and is ascribed to collision sequences involving metastable states of the ions (eN/eNm/ee(N + 1), where N represents an ion of charge multiplicity n). All the breaks observed in the ionization probability curves for [Formula: see text] can be explained in terms of collision sequences involving spectroscopically known metastable levels as limiting steps. Measured ionization potentials of the highly ionized species up to n = 9 are in reasonable agreement with extrapolation of spectroscopic values.

Multiple ionization of the rare gases by successive electron impacts (0–250 eV). II. 1S–2S transition in 3He+

1968 ◽  
Vol 46 (7) ◽  
pp. 865-869 ◽  
Author(s):  
P. A. Redhead ◽  
S. Feser
Keyword(s):  
Electron Energy ◽  
Cross Section ◽  
Mass Spectrometer ◽  
Ion Current ◽  
Rare Gases ◽  
Close Coupling ◽  
Trapped Ion ◽  
Multiple Ionization ◽  
Electron Impacts ◽  
Autoionizing States

The tertiary collision sequence of electrons with helium (He → He+ → He+m(2S) → He2+) has been observed with a trapped-ion mass spectrometer. The variation of He2+ ion current with electron energy shows a threshold at 40.8 eV, and structure, which results from excitation to autoionizing states of the atom below the n = 3 threshold of He+, is observed in the range 45–49 eV. Estimates of the cross section for the 1S–2S transition in He+ lie slightly below the values from close-coupling calculations.

Multiple ionization in carbon monoxide by successive electron impacts

1969 ◽  
Vol 47 (22) ◽  
pp. 2449-2457 ◽  
Author(s):  
P. A. Redhead
Keyword(s):  
Reasonable Agreement ◽  
Energy Levels ◽  
Ion Sources ◽  
Mass Spectrometers ◽  
Trapped Ion ◽  
Appearance Potential ◽  
Multiply Charged ◽  
Multiple Ionization ◽  
Charged Ions ◽  
Potential Curves

Appearance potential curves for the multiply-charged ions of carbon and oxygen (up to C4+ and O6+ for electron energies less than 200 eV) have been measured in two mass spectrometers fitted with trapped-ion sources. Trapping of the C+ and O+ ions is not as efficient as for ions produced without dissociation because of the initial kinetic energies of the dissociatively produced ions. The predominant collision sequences involve the formation of CO+ as the first step rather than the dissociative ionization of CO. Ionization potentials estimated from measured appearance potential curves are in agreement with spectroscopically determined values. Most of the other breaks that were repeatedly observed in the appearance potential curves are in reasonable agreement with energy-limiting steps in the collision sequences corresponding to transitions between spectroscopically known energy levels of the ions. Two observed transitions (in O4+ and O5+ appearance potential curves) cannot be explained in terms of spectroscopically known energy levels and may result from highly-excited, long-lived states of O2+ and O4+, respectively. The threshold of the C4+ appearance potential curve indicates the existence of a metastable state of C3+ not previously observed.

Multiple Ionization of Cesium and Barium by Successive Electron Impacts

1971 ◽  
Vol 49 (5) ◽  
pp. 585-593 ◽  
Author(s):  
P. A. Redhead ◽  
C. P. Gopalaraman
Keyword(s):  
Energy Levels ◽  
Ion Source ◽  
Ionization Potentials ◽  
Ion Currents ◽  
Extrapolation Methods ◽  
Trapped Ion ◽  
Multiply Charged ◽  
Multiple Ionization ◽  
Combined Uncertainty ◽  
Potential Curves

The electron energy dependence of the multiply-charged ion currents of cesium and barium (up to Cs10+ and Ba10+) has been measured in a trapped-ion source mass spectrometer. Approximate values of the higher ionization potentials have been measured which agree with the values predicted by extrapolation methods, to within the combined uncertainty of the experimental and extrapolation methods (~5 V), except for the ionization potential of Ba9+. Improved estimates of higher ionization potentials of ions with atomic number 53–56 have been obtained by the extrapolation method. The energy levels of some long-lived metastable states of Cs and Ba ions were estimated from the measured appearance potential curves.

scholarly journals Upgrading the ECR ion source within FAMA

2018 ◽  
Vol 33 (1) ◽  
pp. 47-52
Author(s):  
Andrey Efremov ◽  
Sergey Bogomolov ◽  
Vladimir Bekhterev ◽  
Aleksandar Dobrosavljevic ◽  
Nebojsa Neskovic ◽  
...  
Keyword(s):  
Electron Cyclotron Resonance ◽  
Ion Beam ◽  
Ion Source ◽  
Vacuum System ◽  
Multiply Charged Ions ◽  
Inlet System ◽  
Multiply Charged ◽  
Microwave System ◽  
Beam Currents ◽  
Charged Ions

Recent upgrading of the Facility for Modification and Analysis of Materials with Ion Beams - FAMA, in the Laboratory of Physics of the Vinca Institute of Nuclear Sciences, included the modernization of its electron cyclotron resonance ion source. Since the old ion source was being extensively used for more than 15 years for production of multiply charged ions from gases and solid substances, its complete reconstruction was needed. The main goal was to reconstruct its plasma and injection chambers and magnetic structure, and thus intensify the production of multiply charged ions. Also, it was decided to refurbish its major subsystems - the vacuum system, the microwave system, the gas inlet system, the solid substance inlet system, and the control system. All these improvements have resulted in a substantial increase of ion beam currents, especially in the case of high charge states, with the operation of the ion source proven to be stable and reproducible.

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