THE EFFECT OF VIBRATIONAL EXCITATION OF H2+ ON ITS COLLISION-INDUCED DISSOCIATION

1964 ◽  
Vol 42 (5) ◽  
pp. 972-979 ◽  
Author(s):  
J. Wm. McGowan ◽  
Larkin Kerwin
Keyword(s):  
Electron Energy ◽  
Cross Section ◽  
Vibrational Excitation ◽  
Collision Induced Dissociation ◽  
Relative Population ◽  
Ion Energy ◽  
Ion Energies ◽  
Vibrational Levels ◽  
Fast Protons ◽  
Franck Condon

A study is reported of the production of fast protons resulting from the collision-induced dissociation of H2+ in collision with H2. Ion energies between 0.6 and 2 kev are considered. For fixed ion energy, a direct relationship is observed between the relative population of the vibrational levels (a function of the ionizing electron energy) and the cross section. As the electron energy is increased, the relative population of the upper states is increased, which gives rise to a marked increase in total cross section. Several mechanisms of ion collisional dissociation obtain. One involves a vertical Franck–Condon transition between electronic states; the other appears to involve a diagonal transition which may occur when Franck–Condon conditions do not apply.

scholarly journals Cross-Section for Proton Transfer from a Large Peptide Ion to Ammonia in the Gas Phase

1990 ◽  
Vol 45 (9-10) ◽  
pp. 1151-1157
Author(s):  
Stephen C. Davis ◽  
Peter J. Derrick ◽  
Christoph Ottinger
Keyword(s):  
Proton Transfer ◽  
Cross Section ◽  
Cyclic Peptide ◽  
Source Region ◽  
Relative Molecular Mass ◽  
Optical Lens ◽  
Ion Energy ◽  
Ion Energies ◽  
Large Peptide ◽  
Large Research

Abstract Proton transfer between ions of the cyclic peptide valinomycin (relative molecular mass 1110.6) and ammonia molecules has been studied over a range of ion energies from 50 eV to 8 keV. Valinomycin ions were produced by field desorption. Collisions of valinomycin ions with ammonia molecules at controlled energies were carried out using an ion-optical lens system situated in the source region of a large research mass spectrometer. The maximum cross-section for proton transfer occurred when the valinomycin ion possessed 1500 eV of kinetic energy. This maximum cross-sec-tion for proton transfer was 3 orders of magnitude smaller than the cross-section for collision-in-duced dissociation of the valinomycin ion at the same ion energy (2.4 • 10-17 cm2 molecule-1 as compared to 2 • 10-14 cm2 molecule-1). A stereospecific stripping model can explain the observa-tions.

Electron capture by fast protons and α-particles in hydrogen

1963 ◽  
Vol 272 (1351) ◽  
pp. 542-556 ◽  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Wave Functions ◽  
Final States ◽  
Resonance Case ◽  
Ion Energies ◽  
The Cross ◽  
Proper Allowance ◽  
Fast Protons ◽  
Α Particles

Cross-sections are calculated for the accidental resonance reaction, He 2+ + H(ls) -> He + (2s or 2p) + H + , and the non-resonance reaction, H + + H (ls)-> H(2s or 2p) + H + by means of the method due to Bates in which account is taken of the non-orthogonality of the wave functions describing the initial and final states. Proper allowance is made for the effects of distortion and of momentum transfer. The calculations are carried out for incident ion energies in the range 25 to 800 keV. In the accidental resonance case, the cross-section is small at low velocities of relative motion, and tends rapidly towards zero as the velocity is decreased in accordance with the prediction of Bates & Lynn. In all processes investigated the effect of distortion is considerable. Using the results of McCarroll & McElroy and of McCarroll for capture into the ground states of He + and H, the cross-sections for capture into all states are estimated. Comparisons are made with the experimental data of Fite, Smith & Stebbings for the incident alpha particle case and with that of Fite, Stebbings, Hummer & Brackman for the incident proton case. The highest energy for which cross-sections are measured in either case is however only 40 keV.

Vibrational excitation influence on the H + BrO → HBr + O reaction: a quasi-classical trajectory investigation

2015 ◽  
Vol 93 (6) ◽  
pp. 602-606 ◽  
Author(s):  
Yingying Zhang ◽  
Ying Shi ◽  
Tingxian Xie ◽  
Zerui Li ◽  
Zhan Hu ◽  
...  
Keyword(s):  
Cross Section ◽  
Rate Constant ◽  
Cross Sections ◽  
Collision Energy ◽  
Vibrational Excitation ◽  
Chem Phys ◽  
Classical Trajectory ◽  
Reaction Probability ◽  
Generalized Polarization ◽  
Vibrational Levels

Quasi-classical trajectory calculations are employed to investigate the vibrational excitation effect on the scalar and vector properties of the H + BrO → HBr + O reaction using a X1A′ state ab initio potential energy surface (J. Chem. Phys. 2000, 113, 4598). The reaction probability, cross section, and rate constant are carried out with the effect of the collision energy (Ecol = 0.1–6 kcal/mol) and vibrational levels (v = 0–3). A significant vibrational dependency has been observed in the reaction probability and cross section at a relatively low collision energy area and has also been found in a low-temperature (T < 150 K) region of the rate constant. In addition, two product angular distributions, P(θr) and P(ϕr), and two generalized polarization-dependent differential cross sections, PDDCS00 and PDDCS20, are calculated as well. All of these scalar and vector properties have shown sensitive behaviors to the vibrational levels.

A Poor Man’s Approach to Semi-Quantitative Analysis with Electron Energy Loss Spectroscopy

1980 ◽  
Vol 38 ◽  
pp. 110-111
Author(s):  
M. Isaacson
Keyword(s):  
Quantitative Analysis ◽  
Energy Loss ◽  
Electron Energy ◽  
Cross Section ◽  
Electron Energy Loss Spectroscopy ◽  
Excitation Cross Section ◽  
Incident Electron ◽  
Integral Cross Section ◽  
Image Position ◽  
Electron Energy Loss

In an earlier paper1 it was found that to a good approximation, the efficiency of collection of electrons that had lost energy due to an inner shell excitation could be written as where σE was the total excitation cross-section and σE(θ, Δ) was the integral cross-section for scattering within an angle θ and with an energy loss up to an energy Δ from the excitation edge, EE. We then obtained: where , with P being the momentum of the incident electron of velocity v. The parameter r was due to the assumption that d2σ/dEdΩ∞E−r for energy loss E. In reference 1 it was assumed that r was a constant.

Altitude dependence of the vibrational distribution of in the nightglow and the possible effects of vibrational excitation in the formation of O(1S)

1984 ◽  
Vol 62 (8) ◽  
pp. 780-788 ◽  
Author(s):  
I. C. McDade ◽  
E. J. Llewellyn ◽  
R. G. H. Greer ◽  
G. Witt
Keyword(s):  
Vibrational Relaxation ◽  
Vibrational Excitation ◽  
Relaxation Model ◽  
Terrestrial Atmosphere ◽  
Transfer Step ◽  
Vibrational Distribution ◽  
Altitude Dependence ◽  
Vibrational Levels ◽  
The Individual

A simple vibrational relaxation model that reproduces the observed vibrational distribution of the [Formula: see text] Herzberg II bands in the terrestrial nightglow is used to derive the altitude profiles of the fractional populations in the individual vibrational levels. Through consideration of these profiles it is shown that if [Formula: see text] is the Barth precursor of O(1S) in the nightglow then, at least in the terrestrial atmosphere, the higher vibrational levels appear to be more effective in the Barth transfer step than the lower vibrational levels.

Collision-Induced Dissociation by Helium:  A Piecewise Construction of the Cross Section

2002 ◽  
Vol 106 (9) ◽  
pp. 1714-1726 ◽  
Author(s):  
L. Poisson ◽  
P. de Pujo ◽  
V. Brenner ◽  
A.-L. Derepas ◽  
J.-P. Dognon ◽  
...  
Keyword(s):  
Cross Section ◽  
Collision Induced Dissociation ◽  
The Cross

scholarly journals The Cross Section for the J = 0 → 2 Rotational Excitation of Hydrogen by Slow Electrons

1969 ◽  
Vol 22 (6) ◽  
pp. 715 ◽  
Author(s):  
RW Crompton ◽  
DK Gibson ◽  
AI McIntosh
Keyword(s):  
Momentum Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Vibrational Excitation ◽  
The Cross ◽  
Excitation Processes ◽  
Slow Electrons ◽  
And Diffusion ◽  
Momentum Transfer Cross Section ◽  
Section Analysis

The results of electron drift and diffusion measurements in parahydrogen have been analysed to determine the cross sections for momentum transfer and for rotational and vibrational excitation. The limited number of possible excitation processes in parahydrogen and the wide separation of the thresholds for these processes make it possible to determine uniquely the J = 0 → 2 rotational cross section from threshold to 0.3 eV. In addition, the momentum transfer cross section has been determined for energies less than 2 eV and it is shown that, near threshold, a vibrational cross section compatible with the data must lie within relatively narrow limits. The problems of uniqueness and accuracy inherent in the swarm method of cross section analysis are discussed. The present results are compared with other recent theoretical and experimental determinations; the agreement with the most recent calculations of Henry and Lane is excellent.

Physical and Chemical Sputtering at Very Low Ion Energy: the Importance of the Sputtering Threshold

1988 ◽  
Vol 129 ◽  
Author(s):  
Christoph Steinbruchel
Keyword(s):  
Threshold Energy ◽  
Surface Binding ◽  
Ion Energy ◽  
Chemical Sputtering ◽  
Surface Binding Energy ◽  
Physical Sputtering ◽  
Chemical Etch ◽  
Ion Energies ◽  
The Difference ◽  
Physical And Chemical

ABSTRACTA variety of data for physical etching (i.e. sputtering) and for ion-enhanced chemical etching of Si and SiO2 is analyzed in the very-low-ion-energy regime. Bombardment by inert ions alone, by reactive ions, and by inert ions in the presence of reactiveneutrals is considered. In all cases the etch yield follows a square root dependence on the ion energy all the way down to the threshold energy for etching. At the same time, the threshold energy has a non-negligible effect on the etch yield even at intermediate ion energies. The difference between physical and ion-enhanced chemical etch yields can be accounted for by a reduction in the average surface binding energy of the etch products and a corresponding reduction in the threshold energy for etching. These results suggest that, in general, the selectivity for ion-enhanced etch processes relative to physical sputtering can be increased significantly at low ion energy.

A measurement of the ionization cross-section of Ne + to Ne 2+ by electron impact

1963 ◽  
Vol 274 (1359) ◽  
pp. 546-551 ◽  
Keyword(s):  
Electron Energy ◽  
Cross Section ◽  
Ionization Cross Section ◽  
Incident Electron Energy ◽  
Ionization Cross ◽  
Maximum Value ◽  
Beam Method ◽  
The Cross ◽  
Semi Empirical ◽  
Limits Of Error

The crossed-beam method described by the authors in 1961 was used to measure the cross-section of Ne + in the reaction Ne + + e → Ne 2+ + 2 e . The cross-section increases linearly with electron energy near the threshold and attains a maximum value of 3·13 x 10 -17 cm 2 at 200 eV. The errors in the measurements were estimated to be less than ± 10% and the highest incident electron energy used was 1000 eV. A semi-empirical formula proposed by Drawin in 1961 describes the measured cross-section within the above limits of error when the two adjustable parameters take the values ξf 1 = 5·25 and f 2 = 0·70.

Electron Energy Dependence of Amorphization in Zr3Fe

1993 ◽  
Vol 316 ◽  
Author(s):  
A.T. Motta ◽  
L.M. Howe ◽  
P.R. Okamoto
Keyword(s):  
Electron Energy ◽  
Cross Section ◽  
Sharp Increase ◽  
Low Dose ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
High Energies ◽  
Intermediate Energies ◽  
Low Energies ◽  
Order Of Magnitude

ABSTRACTThis paper reports the results from a study conducted to determine the effect of electron energy on the dose-to-amorphization of Zr3Fe at 23-30 K. Zr3Fe samples were irradiated in the HVEM at Argonne National Laboratory, at energies ranging from 200 to 900 keV. Amorphization occurred at electron energies from 900 keV down to 250 keV. Three distinct regions were observed: between 900 and 700 keV amorphization occurred at a constant low dose of ~ 4 × 1021 e cm-2; a higher plateau at 1022 was observed between 600 and 400 keV, and finally there was a sharp increase in the dose-to-amorphization below 400 keV, so that at 250 keV the necessary dose was an order of magnitude higher than that at 900 keV. In the region below 400 keV there was evidence of a dependence of the dose-to-amorphization on the orientation of the sample with respect to the electron beam. The results can be analyzed in terms of a composite displacement cross section dominated at high energies by displacements of Zr and Fe atoms, by displacements of Fe atoms at intermediate energies and of secondary displacements of lattice atoms by recoil impurities at low energies.

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