State‐Selected and State‐to‐State Ion‐Molecular Reaction Dynamics by Photoionization and Differential Reactivity Methods

Ng, C. Y.

doi:10.1002/9780470141397.ch6

Cited by 45 publications

(12 citation statements)

References 301 publications

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“…In addition, the peak intensity of the sharp component at the m / z = 29 position is higher than that when there is no C 2 H 4 gas in the gas cell, which is verified by the reaction cross section measurements, indicating that new species with m / z of 29 are formed through reactions rather than C 2 H 5 + / 15 N 14 N + . On the basis of the energetic analysis and previous studies, as well as our experimental observations, the fast and sharp component can be assigned as N 2 H + product ions and the unreacted 15 N 14 N + ions. The TOF peak profile for N 2 H + product ions formed via the H atom transfer stripping mechanism is observed to broaden only mildly compared to that of 15 N 14 N + reactant ions (as well as 14 N 14 N + reactant ions).…”

Section: Resultssupporting

confidence: 70%

“…The development of quantum-state-selected ion–molecule reaction studies in the past decades has rendered a major platform for the investigation of the E cm and the quantum-rovibronic-state effects on chemical reactivity − of ions. The most challenging task for these experiments is to prepare reactant ions into single quantum-rovibronic states and still maintain a sufficiently high intensity for the state-selected ions to undergo single-collision measurements .…”

Section: Introductionmentioning

confidence: 99%

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Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N₂⁺(X²Σ_g⁺: ν⁺= 0–2) + C₂H₄in the Collision Energy Range of 0.05–10.00 eV

Xiong

Chang

et al. 2018

J. Phys. Chem. A

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By implementing a vacuum ultraviolet laser-pulsed field ionization-photoion ion source with a double quadrupole-double octopole ion guide mass filter, we have obtained detailed quantum-vibrational-state-selected integral cross sections σ, ν = 0-2, for the ion-molecule reaction of N(XΣ: ν = 0-2) + CH in the center-of-mass kinetic energy range of E = 0.05-10.00 eV. Three primary product channels corresponding to the formation of CH, CH, and NH ions are identified with their σ values in the order of σ(CH) > σ(CH) > σ(NH). The minor σ(NH) channel is strongly inhibited by E and observed only at E < 0.70 eV. The high σ(CH) and σ(CH) values indicate that CH and CH product ions are formed by prompt dissociation of internally excited CH (CH*) intermediates produced via the near-energy-resonance charge-transfer mechanism. The σ(CH) and σ(CH) are found to drop only mildly or stay nearly constant as a function of E in the range of 0.05-6.00 eV. This observation is contrary to the expectation of a steep decline for the σ value commonly observed for an exothermic reaction pathway as E is increased. Significant vibrational enhancement is observed for the σ(CH) and σ(CH) at ν = 2 and in the E range of ∼0.20-7.00 eV. The branching ratios σ(CH):σ(CH):σ(NH) are also determined with high precision by measuring the intensities of product CH, CH, and NH ions simultaneously at fixed E values. The σ and branching ratio values reported here are useful contributions to the database needed for realistic modeling of the chemical compositions and evolutions of planetary atmospheres, such as the ionosphere of Titian. The quantum-state-selective results can also serve as experimental benchmarks for theoretical calculations on fundamental chemical reaction dynamics.

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Section: Resultssupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N₂⁺(X²Σ_g⁺: ν⁺= 0–2) + C₂H₄in the Collision Energy Range of 0.05–10.00 eV

Xiong

Chang

et al. 2018

J. Phys. Chem. A

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“…The experimental arrangement and procedures of the triple-quadrupole, double-octopole (TQDO) photoionization apparatus for cross-section measurements of state-selected ion−molecule reactions have been described in detail previously. − Briefly, the TQDO apparatus essentially consists of, in sequential order, a vacuum ultraviolet (VUV) photoionization ion source, a reactant quadrupole mass spectrometer (QMS), a lower radio frequency (RF) octopole ion guide reaction gas cell, a middle QMS, an upper RF octopole ion guide reaction gas cell, a product QMS, and a modified Daly-type scintillation ion detector. The TQDO apparatus is partitioned into five chambers, which are separately evacuated by liquid nitrogen or Freon-trapped diffusion pumps.…”

Section: Methodsmentioning

confidence: 99%

Study of the Dissociation of CH₃SCH₃⁺ by Collisional Activation: Evidence of Nonstatistical Behavior

et al. 2002

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The collision-induced dissociation (CID) reaction of CH 3 SCH 3 + + Ar was studied in a triple-quadrupole, double-octopole ion-molecule reaction apparatus. The absolute total cross sections for the product ions CH 2 SH + /CH 3 S + , CH 2 S + , CHS + , and CH 3 + formed in the CID reaction have been measured in the centerof-mass kinetic energy (E cm ) range of 1-19 eV. Using the charge-transfer probing technique, we found that mass-47 product ions are formed in both the CH 2 SH + and CH 3 S + structures. The onsets for CH 2 SH + , CH 3 S + , CH 2 S + , CHS + , and CH 3 + are consistent with their thermochemical thresholds. The formation of the higherenergy product channel CH 3 S + + CH 3 , which involves C-S bond scission, is found to dominate in the E cm range immediately above its onset. The lower-energy channel corresponding to the formation CH 3 SCH 2 + + H is not found. The strong preference observed for the higher-energy channel is in accordance with the conclusions obtained from the CID studies of CH 3 SH + and CH 3 CH 2 SH + , providing further evidence that the CID of CH 3 SCH 3 + is also nonstatistical. The high yield of CH 3 S + + CH 3 is attributed to the more efficient translational-to-vibrational energy transfer for the C-S stretching modes with lower frequencies than to those for the C-H stretching modes with higher frequencies, along with weak coupling between these vibrational modes with significantly different frequencies of CH 3 SCH 3 + . In addition, the dissociation pathways deduced are consistent with the results of ab initio calculations at the G3 level.

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“…The arrangement of the triple−quadrupole double-octopole (TQDO) photoionization ion−molecule reaction apparatus (Figure ) and procedures used to perform state-selected absolute total cross-section measurements have been described in detail previously. − The TQDO apparatus essentially consists of, in sequential order, a vacuum ultraviolet (VUV) photoionization ion source, an electron impact ion source (1), a reactant quadrupole mass spectrometer (QMS) (5), a lower radio frequency (rf) octopole ion guide reaction gas cell (RFOIGGC) [(6) + (7)], a middle QMS (10), an upper RFOIGGC [(11) + (14)], a product QMS (15), and a modified Daly-type scintillation ion detector [(17) + (19) + (20)]. The electron impact ion source is not used in this experiment.…”

Section: Experiments Sectionmentioning

confidence: 99%

Dissociation of CH₃SH⁺by Collisional Activation: Evidence of Nonstatistical Behavior

et al. 1997

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We have measured the absolute total cross sections for CH2SH+(CH3S+), CH2S+, HCS+, HS+, CH3 +, and CH2 + produced by the collision-induced dissociation (CID) reaction of CH3SH+(12A‘‘) + Ar in the center-of-mass collision energy range of 1−36 eV. While the onset for CH3 + is consistent with the thermochemical threshold for the formation of CH3 + + SH, the onsets for other product ions are higher than their corresponding thermochemical thresholds. Using a charge transfer probing technique, we conclude that the m/e = 47 amu ions observed in the CID reaction have mostly the CH2SH+ structure. The relative yields for CH2SH+, CH2S+, HCS+, HS+, CH3 +, and CH2 + formed in the CID reaction, which strongly favor the C−S bond scission process leading to the formation of CH3 + + SH, are significantly different from those measured in previous photoionization and charge exchange studies. Since the CH3 + + SH channel is not among the most stable product channels, this observation suggests that the collision-activated dissociation of CH3SH+ is nonstatistical. The high yield for CH3 + + SH observed in CID is attributed to the more efficient translational to vibrational energy transfer for the C−S stretch than for the C−H stretches of CH3SH+, and to weak couplings between the low-frequency C−S and the high-frequency C−H stretching vibrational modes of CH3SH+. The differences in excitation mechanisms for CH3SH+ via collision activation, photoionization, and charge exchange are responsible for the different fragment ion distributions from CH3SH+ observed in these experiments.

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State‐Selected and State‐to‐State Ion‐Molecular Reaction Dynamics by Photoionization and Differential Reactivity Methods

Cited by 45 publications

References 301 publications

Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N₂⁺(X²Σ_g⁺: ν⁺= 0–2) + C₂H₄in the Collision Energy Range of 0.05–10.00 eV

Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N₂⁺(X²Σ_g⁺: ν⁺= 0–2) + C₂H₄in the Collision Energy Range of 0.05–10.00 eV

Study of the Dissociation of CH₃SCH₃⁺ by Collisional Activation: Evidence of Nonstatistical Behavior

Dissociation of CH₃SH⁺by Collisional Activation: Evidence of Nonstatistical Behavior

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State‐Selected and State‐to‐State Ion‐Molecular Reaction Dynamics by Photoionization and Differential Reactivity Methods

Cited by 45 publications

References 301 publications

Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N2+(X2Σg+: ν+= 0–2) + C2H4in the Collision Energy Range of 0.05–10.00 eV

Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N2+(X2Σg+: ν+= 0–2) + C2H4in the Collision Energy Range of 0.05–10.00 eV

Study of the Dissociation of CH3SCH3+ by Collisional Activation: Evidence of Nonstatistical Behavior

Dissociation of CH3SH+by Collisional Activation: Evidence of Nonstatistical Behavior

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Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N₂⁺(X²Σ_g⁺: ν⁺= 0–2) + C₂H₄in the Collision Energy Range of 0.05–10.00 eV

Quantum-State-Selected Integral Cross Sections and Branching Ratios for the Ion–Molecule Reaction of N₂⁺(X²Σ_g⁺: ν⁺= 0–2) + C₂H₄in the Collision Energy Range of 0.05–10.00 eV

Study of the Dissociation of CH₃SCH₃⁺ by Collisional Activation: Evidence of Nonstatistical Behavior

Dissociation of CH₃SH⁺by Collisional Activation: Evidence of Nonstatistical Behavior