Some observations on the ion–molecule reactions in ethylene

1968 ◽  
Vol 46 (2) ◽  
pp. 101-109 ◽  
Author(s):  
J. J. Myher ◽  
A. G. Harrison
Keyword(s):  
Kinetic Energy ◽  
Ground State ◽  
Relative Importance ◽  
Collision Complex ◽  
Ion Molecule Reactions ◽  
Secondary Ions ◽  
Secondary Ion

The ion–molecule reactions in ethylene have been studied under conditions where C2H4+ was the only primary ion. In addition to the expected secondary ions C3H5+ and C4H7+, the C3H4+, C2H2+, and C2H3+ ions have been detected, presumably formed by the reactions[Formula: see text]Reactions [b] and [c] are endothermic for ground state reactants and it has been shown that the kinetic energy of the reactant ion plays a major role in determining the relative importance of these endothermic reactions.The C5H9+ ion has been shown to originate by further reaction of the C3H5+ secondary ion rather than by reaction of the (C4H8+)* collision complex. The reversion of the (C4H8+)* complex to reactants has been confirmed by the observation of isotopically mixed ethylene ions in C2H4–C2D4 mixtures.

Applications of Time-OF-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)

1990 ◽  
Vol 48 (2) ◽  
pp. 308-309
Author(s):  
Bruno Schueler ◽  
Robert W. Odom
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Structural Information ◽  
Time Of Flight ◽  
Biological Tissues ◽  
Polymer Surfaces ◽  
Tof Sims ◽  
Secondary Ions ◽  
Ion Mass Spectrometry ◽  
Secondary Ion

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) provides unique capabilities for elemental and molecular compositional analysis of a wide variety of surfaces. This relatively new technique is finding increasing applications in analyses concerned with determining the chemical composition of various polymer surfaces, identifying the composition of organic and inorganic residues on surfaces and the localization of molecular or structurally significant secondary ions signals from biological tissues. TOF-SIMS analyses are typically performed under low primary ion dose (static SIMS) conditions and hence the secondary ions formed often contain significant structural information.This paper will present an overview of current TOF-SIMS instrumentation with particular emphasis on the stigmatic imaging ion microscope developed in the authors’ laboratory. This discussion will be followed by a presentation of several useful applications of the technique for the characterization of polymer surfaces and biological tissues specimens. Particular attention in these applications will focus on how the analytical problem impacts the performance requirements of the mass spectrometer and vice-versa.

scholarly journals Some Key Issues in Hypersonic Propulsion

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3690
Author(s):  
Claudio Bruno ◽  
Antonella Ingenito
Keyword(s):  
Kinetic Energy ◽  
Constant Volume ◽  
Supersonic Combustion ◽  
Relative Importance ◽  
Friction Drag ◽  
Wave Versus ◽  
Hypersonic Propulsion ◽  
Key Issues ◽  
Drag Ratio ◽  
Critical Aspects

This paper summarizes and discusses some critical aspects of flying hypersonically. The first is the L/D (lift over drag) ratio determining thrust and that in turn depends on the slenderness Küchemann’s τ parameter. This second parameter is found to depend on the relative importance of wave versus friction drag. Ultimately, all engineering drag is argued to depend on vorticity formed at the expense of the vehicle kinetic energy, thus requiring work by thrust. Different mixing strategies are discussed and shown to depend also on mechanisms forming vorticity when the regime is compressible. Supersonic combustion is briefly analyzed and found, at sufficiently high combustor Mach, to take place locally at constant volume, unlike conventional Brayton cycles.

VUV FRAGMENTATION OF SOME HYDROFLUOROCARBON CATIONS STUDIED USING COINCIDENCE TECHNIQUES

2002 ◽  
Vol 09 (01) ◽  
pp. 153-158 ◽  
Author(s):  
WEIDONG ZHOU ◽  
D. P. SECCOMBE ◽  
R. Y. L. CHIM ◽  
R. P. TUCKETT
Keyword(s):  
Kinetic Energy ◽  
Ab Initio ◽  
Ground State ◽  
Lower Energy ◽  
Lone Pair ◽  
Electronic States ◽  
Photoelectron Spectra ◽  
Highest Occupied Molecular Orbital ◽  
Impulsive Model ◽  
Lone Pair Electrons

Threshold photoelectron–photoion coincidence (TPEPICO) spectroscopy has been used to investigate the decay dynamics of the valence electronic states of the parent cation of several hydrofluorocarbons (HFC), based on fluorine-substituted ethane, in the energy range 11–25 eV. We present data for CF 3– CHF 2, CF 3– CH 2 F , CF 3– CH 3 and CHF 2– CH 3. The threshold photoelectron spectra (TPES) of these molecules show a common feature of a broad, relatively weak ground state, associated with electron removal from the highest-occupied molecular orbital (HOMO) having mainly C–C σ-bonding character. Adiabatic and vertical ionisation energies for the HOMO of the four HFCs are presented, together with corresponding values from ab initio calculations. For those lower-energy molecular orbitals associated with non-bonding fluorine 2pπ lone pair electrons, these electronic states of the HFC cation decay impulsively by C–F bond fission with considerable release of translational kinetic energy. Appearance energies are presented for formation of the daughter cation formed by such a process (e.g. CF 3– CHF +), together with ab initio energies of the corresponding dissociation channel (e.g. CF 3– CHF + + F ). Values for the translational kinetic energy released are compared with the predictions of a pure-impulsive model.

Fragmentation of alkoxide ions following collisional activation. An energy-resolved study

1988 ◽  
Vol 66 (11) ◽  
pp. 2947-2953 ◽  
Author(s):  
Roger S. Mercer ◽  
Alex G. Harrison
Keyword(s):  
Kinetic Energy ◽  
Collisional Activation ◽  
Collision Energy ◽  
Relative Importance ◽  
Elimination Reaction ◽  
Proton Abstraction ◽  
Relative Stabilities ◽  
Collisionally Activated Dissociation ◽  
Reaction Channels ◽  
Alkane Elimination

The collisionally activated dissociation reactions of the C2 to C5 alkoxide ions have been studied for collisons occurring at 8 keV kinetic energy and also over the range 5 to 100 eV kinetic energy. The alkoxide ions fragment by 1,2-elimination of H2 and/or an alkane. Thus, primary alkoxide ions fragment by elimination of H2 only, secondary alkoxide ions show elimination of H2 and alkane molecules, while tertiary alkoxide ions show elimination of alkanes only. In alkane elimination, loss of CH4 is much more facilie than loss of larger alkanes. For secondary alkoxide ions, where more than one elimination reaction occurs, the energy dependence of fragmentation has been explored over the collision energy range 5 to 100 eV. The results are interpreted in terms of a step-wise mechanism involving formation of an anion-carbonyl compound ion-dipole complex, followed by proton abstraction by the H− or alkyl anion leading to the final products. The relative importance of the reaction channels is determined by the relative stabilities of these ion-dipole complexes.

scholarly journals Stimulated Processes in a Half-collision

1986 ◽  
Vol 5 (6) ◽  
pp. 393-406
Author(s):  
H. H. Telle
Keyword(s):  
Kinetic Energy ◽  
Quantum State ◽  
Ground State ◽  
Diatomic Molecules ◽  
Dye Laser ◽  
Interatomic Potentials ◽  
Repulsive Potential ◽  
Induced Absorption ◽  
Tunable Dye Laser

Selective photodissociation of diatomic molecules is used to prepare the separating species in a well defined quantum state with narrowly determined final kinetic energy of the particles. During the course of separation to products the repulsive potential is probed by a tunable dye laser, that is by induced absorption in case the dissociation proceeds on a potential leading to ground state products, or by induced emission or absorption for all other cases. The determination of interatomic potentials from the observed spectra is discussed.

Dissociative Electron Attachment Processes in SO2 and NO2

1971 ◽  
Vol 49 (9) ◽  
pp. 1571-1574 ◽  
Author(s):  
D. A. Rallis ◽  
J. M. Goodings
Keyword(s):  
Kinetic Energy ◽  
Ground State ◽  
Electronic Excitation ◽  
Electron Attachment ◽  
Negative Ion ◽  
Dissociation Limit ◽  
Dissociative Electron Attachment ◽  
Zero Kinetic Energy ◽  
Trapped Electron ◽  
Second Peak

A trapped electron apparatus has been used to identify the processes involved in negative ion formation for the triatomic oxides SO2 and NO2. Two O− peaks are observed in SO2 with onset values at 4.2 ± 0.15 and 6.3 ± 0.2 eV, and peak values at 5.0 ± 0.15 and 7.4 ± 0.15 eV, respectively. From kinetic energy analysis of the O− ions, both peaks are found to have the same dissociation limit involving SO in its ground state. For NO2, two dissociative electron attachment peaks are observed with onset values at 1.6 ± 0.2 and 7.3 ± 0.3 eV, and peak values at 3.0 ± 0.2 and 8.1 ± 0.2 eV, respectively. The first broad peak is explained by overlapping contributions from two processes having the same dissociation limit involving ground state NO; they differ only in the amount of kinetic energy possessed by the fragments. The second peak appears to involve electronic excitation of the neutral fragment NO* with zero kinetic energy at onset.

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