Vibrational excitation of N<sub>2</sub> by C<sup>+</sup> ions

Lee, A. R.; Enos, C.S.; Brenton, A.G.

doi:10.1002/rcm.1290040704

Cited by 10 publications

(5 citation statements)

References 6 publications

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“…Moreover, as we have already pointed out in some previous papers, the quantification limits claimed were always extrapolated from a non-significant 3 : 1 signal-to-noise ratio, or more often from a much higher tested concentration. These quantification limits were not calculated on the basis of a suitable repeatability assay combined with a commonly accepted statistical test, as required by most of the regulatory agencies like the Food and Drug Administration.8-' 6 We have developed a GC/MS assay in the NICI mode with methane as the reagent gas. GC was performed using a falling needle injector connected to a non-polar high-resolution capillary column.…”

Section: Introductionmentioning

confidence: 99%

A highly sensitive assay of melatonin at the femtogram level in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry

Fourtillan

Gobin

Faye

et al. 1994

Biol. Mass Spectrom.

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A highly sensitive and specific assay was developed for routine analysis of melatonin at the femotogram level in human plasma. Melatonin and the deuterated internal standard [(2H4)melatonin] were measured by gas chromatography/negative ion chemical ionization mass spectrometry with methane as the reagent gas. A simple liquid-liquid extraction procedure was used to isolate the two compounds of interest from the complex biological matrix. Melatonin was converted to the fluorinated derivative with pentafluoropropionic anhydride. The mass spectrometer was tuned to monitor the very intense and stable ions at m/z 320 and 323 which were generated into the ion source by a dissociative capture process. This assay was conducted with 1 ml of plasma and the quantification limit of the method was statistically calculated as 0.5 pg ml-1. The very low relative standard deviations and mean percentages of error calculated during the within-day or between-day repeatability assays have clearly demonstrated the ruggedness of the technique for the routine quantitative measurement of melatonin in plasma. Some results on the melatonin circadian rhythm are presented to illustrate the applicability of this powerful gas chromatographic/mass spectrometric method.

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Section: Introductionmentioning

confidence: 99%

A highly sensitive assay of melatonin at the femtogram level in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry

Fourtillan

Gobin

Faye

et al. 1994

Biol. Mass Spectrom.

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“…Intriguingly, features 11-V, which peak at energy losses of 11.2 eV, 6.2 eV, ~4 . 5 eV and ~2 . 8 eV respectively, appear to result from excitation of the X'Cg+-+B311g (Wilkinson) system There are seven main features in the translational energy spectrum of 3 keV Cl+ ions scattered off N2 (Fig.…”

Section: Translational-energy Spectra Of Singlet Ground State Targetsmentioning

confidence: 99%

“…35 are shown in Figs 1 to 7 and are interpreted with the aid of the spin rule. The observed reaction channels are identified and summarized in Table 1.…”

Section: Translational-energy Spectra Of Singlet Ground State Targetsmentioning

confidence: 99%

Translational energy spectroscopy. Spin‐conservation studies in collisional excitation processes

Enos

Lee

Brenton

1995

Rapid Comm Mass Spectrometry

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High-resolution translational energy spectroscopy is an effective means of obtaining detailed state-selective information, permitting systematic investigation of spin conservation in collisional processes. In this paper, we examine collisional excitation of one selected singlet (N3 and one non-singlet ( 0 3 target by a variety of projectile ions, providing a kaleidoscope of assorted effects.The concept of spin conservation in collisional processes first appeared in an article on quantum mechanics written by Eugene Wigner during his Goettingen period,' and has been the subject of numerous studies ever since. Early experimental support for spin conservation came from the work of Beutler and Eisenschimme12 who monitored the triplet and singlet radiations emitted by excited mercury atoms in a gaseous discharge. They found that addition of metastable krypton ('P) to the discharge enhanced the triplet radiation without substantially affecting the intensity of the singlet radiation. This can be understood in terms of the multiplicities of the participating atoms in the two processes:The first of these is in accord with the spin-conservation requirement and therefore leads to enhancement of the triplet radiation, whereas the second process violates spin conservation and is accordingly suppressed. Contemporary investigations by M~o r e~.~ for inelastic collisions of N+ ions with inert gas atoms and diatomic molecules (N, and 0,) revealed that spin conservation was generally observed for all excitation and deexcitation processes, except for some weak spin violation attributed to strong spin-orbit coupling in the relevant ion-atom/ion-molecule systems. However, one of their reported spin non-conserved processes, involving the simultaneous atomic N+('D+ IS) and molecular 0,(X3X;+ G 'Ag) transitions in N+-02, was not detected in our recent high-resolution studies of this collision ~y s t e m .~ In single electron capture, studies by Sat0 and Moore6 on capture by N2+ in He and Ne also confirmed spin conservation in all observed channels. This is in accord with our own recent investigation of single electron capture (SEC) by N2+ ions, as well as SEC by C2+, C3+ and 02+ from He, Ne and Ar By contrast, double electron capture (DEC) processes are often associated with spin violation. This is exemplified by the observation of Fourier et a[." in DEC collisions of H' with Xe atoms in translationalenergy studies. Our own studies involving double electron capture by Xe3+ and Kr3+ in Ar and KrI2 and Ar4+ states is strictly forbidden with the 2H+ and He2+ product target ions being permanent singlets. They found that the results for collisions of He2+ with H2 were in accord with the spin rule, but significant triplet emissions following He2+/He collisions indicated a spin violation and were attributed to the dominations of short range effects. Our current observations", l3 appear to support this view.The Wigner spin-conservation rule', 4, l9 requires that the total spin angular momentum should remain unchanged in the course of a collision...

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“…2.4) were resolved by electrophoresis under NR conditions on 12% polyacrylamide gels.The gels were then briefly stained with 0 . 3~ CuC12 [22], and the bands corresponding to gp23, gp45 and gp90 were excised. When rerun on a 10% SDS gel, all three glycoproteins resolved as single, welldefined bands (not shown).…”

Section: Purification Of Individual Glycoproteinsmentioning

confidence: 99%

A novel thymic epithelial adhesion molecule

1990

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Interactions between thymocytes and thymic stromal cells are responsible for positive and negative selection of T cell, their differentiation, maturation and proliferation. The signals required for these events to occur often necessitate close contact, and indeed adhesion, between the cell types involved. The identification of specific adhesion molecules in this context, is, therefore, a vital first step in determining the nature of the signal they mediate or facilitate at a given stage of differentiation. In the present work we identify, isolate and partially characterize a ligand present on thymic medullary epithelial cells which selectively binds CD4+ CD8+ thymocytes found primarily in the thymic cortex. This adhesion molecule is composed of two non-covalently associated glycoproteins of 23 kDa and 45 kDa, respectively, both of which are needed to bind to thymocytes. The importance of the finding is that the ligand, in isolated immobilized form, binds the same thymocyte subset as the original epithelial cell line from which it was isolated. The CD4+ CD8+ thymocyte subset is the precursor of single-positive mature T cells; hence the putative biological activity of the ligand in question takes place at a pivotal stage of T cell differentiation.

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Vibrational excitation of N₂ by C⁺ ions

Cited by 10 publications

References 6 publications

A highly sensitive assay of melatonin at the femtogram level in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry

A highly sensitive assay of melatonin at the femtogram level in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry

Translational energy spectroscopy. Spin‐conservation studies in collisional excitation processes

A novel thymic epithelial adhesion molecule

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Vibrational excitation of N2 by C+ ions

Cited by 10 publications

References 6 publications

A highly sensitive assay of melatonin at the femtogram level in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry

A highly sensitive assay of melatonin at the femtogram level in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry

Translational energy spectroscopy. Spin‐conservation studies in collisional excitation processes

A novel thymic epithelial adhesion molecule

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Vibrational excitation of N₂ by C⁺ ions