Electronic and vibrational excitation of N2 by O+ and N+

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

doi:10.1016/0009-2614(90)80084-q

Chemical Physics Letters

1990

DOI: 10.1016/0009-2614(90)80084-q

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Electronic and vibrational excitation of N2 by O+ and N+

A.R. Lee

C.S. Enos

A.G. Brenton

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Cited by 5 publications

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“…9 Early studies [42][43][44][45][46][47] highlighted its utility as a spectroscopic tool for the study of ionic species directly, for example, the 'Raman-like' vibronic excitation/de-excitation bands seen for NO 2 + . 48 Some systems were found to be less tractable, where dissociation occurs rapidly after excitation; CO 2 + 45 shows a featureless TES spectrum indicating no evidence for long-lived states ( ≥ 0.1 µs) amongst the manifold of low-lying singlet and triplet states.…”

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confidence: 99%

The design and performance of a high resolution translational energy loss spectrometer

Brenton

Lock

1997

Rapid Commun. Mass Spectrom.

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An instrumental development is described that achieved high energy resolving power when studying collisions between fast ion beams, at keV energies, interacting with thermal molecular and atomic gaseous targets. This technique is referred to as translational energy spectroscopy (TES) and can reveal spectroscopic information on the states of the participating species, the dynamics of the collision, lifetimes of species formed, state-to-state collision cross-sections and populations of states. The instruments described are based on an unique symmetrical arrangement of cylindrical electrostatic analysers. These are placed in a double focusing ion-optical geometry leading to very small first and second order image aberrations, sufficient to obtain a primary energy resolving power of 10 5 . Two such instruments were developed and their relative performances are compared experimentally and through computer modelling; the second, and larger, instrument has an improved sensitivity by an order of magnitude and a three times increase in resolving power. This has enabled collision spectroscopy to achieve performance similar to electron energy-loss spectroscopy and photoelectron spectroscopy, with a resolution on the unscattered ion beam measured to be 0.01 eV, at 3 keV collision energy, on energy loss processes of ≥ 0.03 eV. These developments allow TES to observe, (i) the vibrational/electronic spectroscopy of keV ion/molecule collisions; (ii) spin-selective spectra; (iii) the highly excited states close to and beyond the ionization limit of the target species; and (iv) involatile targets using a high temperature cell. The validity of optical quantum selection rules, relying on the electric-dipole interaction governing photon-induced transitions, has been tested for TES, which relies on the more general ion/neutral interaction potential responsible for collisional excitation. Spin conservation was found to be strongly adhered to, whilst orbital angular momentum and total angular momentum were not. The specific selection rules for homonuclear diatomics g < -> g and u < -> u were found to be allowed in TES, in contradiction to the case of optical spectroscopy, whilst there was some preliminary evidence that the optical Σ + -Σ -symmetry-forbidden transition was also forbidden for the TES reactions studied. For H 2 + projectiles, excitation to triplet states is strongly favoured over excitation to singlet states.

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confidence: 99%

The design and performance of a high resolution translational energy loss spectrometer

Brenton

Lock

1997

Rapid Commun. Mass Spectrom.

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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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Breakdown of spin conservation for collisions of chlorine ions with atomic and molecular gases

Enos

Lee

Brenton

1991

International Journal of Mass Spectrometry and Ion Processes

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Electronic and vibrational excitation of N2 by O+ and N+

Cited by 5 publications

References 4 publications

The design and performance of a high resolution translational energy loss spectrometer

The design and performance of a high resolution translational energy loss spectrometer

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

Breakdown of spin conservation for collisions of chlorine ions with atomic and molecular gases

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