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Existence of an exceptional reaction pathway for H3 + formation observed in collision-induced dissociation of methane ions at 1000 eV
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10.1063/1.3553200
/content/aip/journal/jcp/134/6/10.1063/1.3553200
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/6/10.1063/1.3553200

Figures

Image of FIG. 1.
FIG. 1.

Schematic of the experimental setup. The scattered ions were analyzed at the detection angle θ using an electrostatic energy analyzer A, which rotated around the center of the ion–gas crossing point. The energy resolution EE of the analyzer is 100. The inset shows detail of the ion–gas collision space. Ar or He gas was introduced into the chamber using a gas flow tube B, and the energetic CH4 + or CH3 + ion beam was directed into the chamber through the ion beam hole.

Image of FIG. 2.
FIG. 2.

A typical ion spectrum of methane ions selected using the magnetic sector mass-analyzer as a function of the magnet current, which was obtained using the electron bombardment ion gun operated at bias voltage (acceleration voltage) of 500 V.

Image of FIG. 3.
FIG. 3.

(a) The full range spectrum of the collision-induced dissociation of CH4 + at 1000 eV with Ar, which was measured at a detection angle of 15°. (b) and (c) Low and high energy regions of spectrum (a), respectively, and the solid curves show Gaussian fitting of each peak.

Image of FIG. 4.
FIG. 4.

Spectra in the collision-induced dissociation of CH4 + at 1000 eV with Ar, which were measured at a detection angle of 0°. Solid curves are from Gaussian fitting. (a) The high energy region spectrum. The peaks of CH3 + and CH4 + are not shown because they were too intense. (b) The low energy region spectrum.

Image of FIG. 5.
FIG. 5.

Energies of the five hydrocarbon fragments as a function of scattering angle. The marked points indicate the energies of the peaks obtained by Gaussian fitting of the experimental data. The solid marked points correspond to the experiments performed with a CH4 + beam current of 10 nA, and the open marked points are for a CH4 + beam current of 1nA. The solid and dotted lines are theoretical values calculated by Eqs. (1) and (2), and the dotted line includes the energy loss due to C–H bond breaking.

Image of FIG. 6.
FIG. 6.

Energies of the three hydrogen fragments as a function of scattering angle. The solid marked points are the energies of the peaks obtained by Gaussian fitting from experimental spectra obtained with a CH4 + ion beam current of 10 nA. The solid lines are theoretical values calculated by Eqs. (1) and (2).

Image of FIG. 7.
FIG. 7.

The spectra for the collision-induced dissociation of CH4 + at 1000 eV with Ar at a beam current of 1 nA, which were measured at a detection angle of 0°. Solid curves are from Gaussian fitting. (a) The high energy region spectrum and (b) an enlargement of the high energy region spectrum.

Image of FIG. 8.
FIG. 8.

The 12–6–4 potential (Ref. 17) V(r) for the CH4 + + Ar system derived from the equation, V(r) = ε|(1 + γ)(r m  /r)12 − 4γ(r m /r)6 − 3 (1 − γ)(r m /r)4|/2, where ε is the depth of the potential well, r m is the interatomic distance at the potential minimum, and γ is an adjustable force parameter ranging from 1 to 0. For the calculation, ε = 3.0 eV, r m = 2.4 Å, and γ = 0.5 were used.

Image of FIG. 9.
FIG. 9.

The deflection function θ(b)for the 1000 eV CH4 +–Ar system which is calculated using the interaction potential V(r) of Fig. 8, where it is assumed that no attractive force works between partners when the impact parameter is over 40 Å.

Image of FIG. 10.
FIG. 10.

(a) The full range spectrum of the collision-induced dissociation of CH3 + at 1000 eV with Ar, which were measured at a scattering angle of 15°. (b) and (c) Low and high energy regions of spectrum (a), respectively. Solid curves are the result of Gaussian fitting.

Image of FIG. 11.
FIG. 11.

The H+, H2 +, and H3 + fragments as a function of the scattering angle during collision of 1000 eV CH4 + with Ar. The CH4 + ion beam current was 10 nA.

Image of FIG. 12.
FIG. 12.

(a) The H+, H2 +, and H3 + fragments obtained after collision of 1000 eV CH3 + with Ar at a scattering angle of zero. The CH3 + ion beam current was 10 nA. (b) The enlarged spectrum of the region from 100 to 300 eV. The solid lines show the result of Gaussian fitting.

Image of FIG. 13.
FIG. 13.

(a) Schematic illustration of the fragmentation in the collision-induced dissociation of CH4 + under the rainbow scattering (θ = 0.21°). (b) Structure of CH4 + with T d symmetry. (c) Structure of CH4 + with C 2v symmetry.

Tables

Generic image for table
Table I.

Observed peak energies (Obs.) of the ionized fragments from 1000 eV CH4 + at the beam current of 10 nA. Calc. shows the calculated energies at the scattering angle of 15° using Eqs. (1) and (2) in text, and Calc.* shows the calculated energies by taking into account the energy loss due to the breaking of C–H bond, respectively, All energies are in eV.

Generic image for table
Table II.

The values of Obs., Calc., and Calc.* for the ionized fragments from 1000 eV CH4 + at the beam current of 10 nA taken at the scattering angle of 12°. All energies are in eV.

Generic image for table
Table III.

The values of Obs., Calc., and Calc.* for the ionized fragments from 1000 eV CH4 + at the beam current of 10 nA taken at the scattering angle of 6°. All energies are in eV.

Generic image for table
Table IV.

The values of Obs., Calc., and Calc.* for the ionized fragments from 1000 eV CH4 + at the beam current of 10 nA taken at the scattering angle of 3°. All energies are in eV.

Generic image for table
Table V.

The values of Obs., Calc., and Calc.* for the ionized fragments from 1000 eV-CH4 + at the beam current of 10 nA taken at the scattering angle of 0°. All energies are in eV.

Generic image for table
Table VI.

The values of Obs., Calc. and Calc.* for the ionized hydrocarbon fragments from 1000eV-CH4 + at the beam current of 1nA taken at the scattering angle of 0°. All energies are in eV.

Generic image for table
Table VII.

The values of Obs., Calc., and Calc.* for the ionized fragments from 1000 eV-CH3 + at the beam current of 10 nA taken at the scattering angle of 15°. All energies are in eV.

Generic image for table
Table VIII.

Observed peak intensity of the ionized hydrogen fragments for 1000 eV-CH4 + ions at the beam current of 10 nA under the scattering angle conditions of 0°, 3°, and 9°.

Generic image for table
Table IX.

Counters of the T d and C 2v symmetries in CH4 + ion on the H3 + potential surface (Ref. 29) in the S a S x plane of distortions (R 23 = R 31: isosceles triangle).

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/content/aip/journal/jcp/134/6/10.1063/1.3553200
2011-02-10
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Existence of an exceptional reaction pathway for H3+ formation observed in collision-induced dissociation of methane ions at 1000 eV
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/6/10.1063/1.3553200
10.1063/1.3553200
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