Sequential-impact mass spectrometry; pressure dependence of ion currents from trapped-ion sources

1970 ◽  
Vol 48 (16) ◽  
pp. 1906-1916 ◽  
Author(s):  
P. A. Redhead
Keyword(s):  
Cross Sections ◽  
Ion Source ◽  
High Electron ◽  
Ion Currents ◽  
Trapped Ion ◽  
Positive Ions ◽  
Ion Escape ◽  
Electron Current Density ◽  
12 Steps ◽  
Ion Collision

Positive ions can be trapped by electron space–charge fields in the ion-source of a mass spectrometer resulting in electron–ion collision sequences. With high electron current density (~0.5 A cm−2) and potential barriers to prevent ion escape along the axis of the electron beam, the trapping time can be increased sufficiently so that collision sequences with as many as 12 steps are observed.A simple model of the behavior of a trapped-ion source has been developed and solutions for the ion currents as a function of pressure obtained. The predictions of the model are compared with experimental results for neon and argon and approximate agreement obtained. Approximate values of cross sections for ionization and excitation of ions can be obtained by fitting the predictions of the model to the measured ion current vs. pressure curves.

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 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 Identification of N-glycans with GalNAc-containing antennae from recombinant HIV trimers by ion mobility and negative ion fragmentation

2021 ◽  
Author(s):  
David J. Harvey ◽  
Anna-Janina Behrens ◽  
Max Crispin ◽  
Weston B. Struwe
Keyword(s):  
Cross Sections ◽  
Ion Mobility ◽  
Travelling Wave ◽  
Negative Ion ◽  
Ion Fragmentation ◽  
Structural Identity ◽  
Immunodeficiency Virus ◽  
Different Types ◽  
Complex Glycans ◽  
Ion Collision

AbstractNegative ion collision-induced dissociation (CID) of underivatized N-glycans has proved to be a simple, yet powerful method for their structural determination. Recently, we have identified a series of such structures with GalNAc rather than the more common galactose capping the antennae of hybrid and complex glycans. As part of a series of publications describing the negative ion fragmentation of different types of N-glycan, this paper describes their CID spectra and estimated nitrogen cross sections recorded by travelling wave ion mobility mass spectrometry (TWIMS). Most of the glycans were derived from the recombinant glycoproteins gp120 and gp41 from the human immunodeficiency virus (HIV), recombinantly derived from human embryonic kidney (HEK 293T) cells. Twenty-six GalNAc-capped hybrid and complex N-glycans were identified by a combination of TWIMS, negative ion CID, and exoglycosidase digestions. They were present as the neutral glycans and their sulfated and α2→3-linked sialylated analogues. Overall, negative ion fragmentation of glycans generates fingerprints that reveal their structural identity.

Electron impact excitation of positive ions

1970 ◽  
Vol 266 (1175) ◽  
pp. 225-279 ◽  
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Nuclear Charge ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Positive Ions ◽  
Relativistic Coulomb ◽  
Hydrogenic Ions

Non-relativistic Coulomb-Born-Oppenheimer reactance matrices and cross-sections are given for all transitions between the Is, 2s and 2p states in He+ and in hydrogen-like ions of large nuclear charge. From these results some cross-sections for intercombination transitions in highly charged non-hydrogenic ions are estimated.

Negative-Ion Implantation

1994 ◽  
Vol 354 ◽  
Author(s):  
Junzo Ishikawa
Keyword(s):  
Ion Implantation ◽  
Negative Ions ◽  
Ion Source ◽  
Negative Ion ◽  
Rf Plasma ◽  
Ion Currents ◽  
Promising Technique ◽  
Surface Charging ◽  
Silicon Carbon ◽  
A Charge

AbstractNegative-ion implantation is a promising technique for forthcoming ULSI (more than 256 M bits) fabrication and TFT (for color LCD) fabrication, since the surface charging voltage of insulated electrodes or insulators implanted by negative ions is found to saturate within so few as several volts, no breakdown of insulators would be expected without a charge neutralizer in these fabrication processes. Scatter-less negative-ion implantation into powders is also possible. For this purpose an rf-plasma-sputter type heavy negative-ion source was developed, which can deliver several milliamperes of various kinds of negative ion currents such as boron, phosphor, silicon, carbon, copper, oxygen, etc. A medium current negative-ion implanter with a small version of this type of ion source has been developed.

scholarly journals Online parallel accumulation − serial fragmentation (PASEF) with a novel trapped ion mobility mass spectrometer

2018 ◽  
Author(s):  
Florian Meier ◽  
Andreas-David Brunner ◽  
Scarlet Koch ◽  
Heiner Koch ◽  
Markus Lubeck ◽  
...  
Keyword(s):  
Cross Sections ◽  
Ion Mobility ◽  
Large Scale ◽  
High Efficiency ◽  
Low Voltage ◽  
Shotgun Proteomics ◽  
Trapped Ion ◽  
Operating Modes ◽  
Third Dimension ◽  
Mobility Device

ABSTRACTIn bottom-up proteomics, peptides are separated by liquid chromatography with elution peak widths in the range of seconds, while mass spectra are acquired in about 100 microseconds with time-of-fight (TOF) instruments. This allows adding ion mobility as a third dimension of separation. Among several formats, trapped ion mobility spectrometry (TIMS) is attractive due to its small size, low voltage requirements and high efficiency of ion utilization. We have recently demonstrated a scan mode termed parallel accumulation – serial fragmentation (PASEF), which multiplies the sequencing speed without any loss in sensitivity (Meier et al., PMID: 26538118). Here we introduce the timsTOF Pro instrument, which optimally implements online PASEF. It features an orthogonal ion path into the ion mobility device, limiting the amount of debris entering the instrument and making it very robust in daily operation. We investigate different precursor selection schemes for shotgun proteomics to optimally allocate in excess of 100 fragmentation events per second. More than 800,000 fragmentation spectra in standard 120 min LC runs are easily achievable, which can be used for near exhaustive precursor selection in complex mixtures or re-sequencing weak precursors. MaxQuant identified more than 6,400 proteins in single run HeLa analyses without matching to a library, and with high quantitative reproducibility (R > 0.97). Online PASEF achieves a remarkable sensitivity with more than 2,900 proteins identified in 30 min runs of only 10 ng HeLa digest. We also show that highly reproducible collisional cross sections can be acquired on a large scale (R > 0.99). PASEF on the timsTOF Pro is a valuable addition to the technological toolbox in proteomics, with a number of unique operating modes that are only beginning to be explored.

Merging beams study of ionization of positive ions by electrons

1972 ◽  
Vol 327 (1570) ◽  
pp. 317-328 ◽  
Keyword(s):  
Experimental Data ◽  
Energy Range ◽  
Cross Sections ◽  
Atomic Nitrogen ◽  
Efficiency Curve ◽  
Entire Energy Range ◽  
Positive Ions ◽  
Entire Energy ◽  
Product Ions ◽  
Scaling Rule

The technique of beam superposition is employed in the experimental study of ionization of He+, N+ and 0+ by electrons. The electron energy range extends up to 300 eV. The primary and product ions are mass selected. Relative cross-sections for ionization are obtained as a function of the laboratory energy of the electrons. The experimental data for He+ and N+ are quite consistent with published values of the absolute cross-sections for these systems. By using Thomson’s classical scaling rule for isoelectronic systems, the cross-sections for ionization of O+ are calculated from those for ionization of atomic nitrogen. These values, when normalized to the relative ionization efficiency curve obtained experimentally here, show close overlap over the entire energy range.

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