Temperature effects in the collisional deactivation of highly vibrationally excited pyrazine by unexcited pyrazine

Miller, Laurie A.; Cook, Carolyn; Barker, John R.

doi:10.1063/1.472173

Cited by 38 publications

(42 citation statements)

References 41 publications

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“…[20][21][22][23][24] Others have monitored the uptake of energy in the bath medium during the relaxation by various techniques [25][26][27][28][29][30][31][32][33][34] or even identified state-specifically the energy transferred, e.g., to CO 2 colliders in single collisions. [35][36][37][38][39][40][41][42] The vast majority of those data are on ͗⌬E͘, the average amount of energy transferred per collision.…”

Section: Introductionmentioning

confidence: 99%

Collisional energy transfer probabilities of highly excited molecules from kinetically controlled selective ionization (KCSI). II. The collisional relaxation of toluene: P(E′,E) and moments of energy transfer for energies up to 50 000 cm−1

Lenzer

Luther

Reihs

et al. 2000

The Journal of Chemical Physics

108

156

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Complete and detailed experimental transition probability density functions P(E′,E) have been determined for the first time for collisions between a large, highly vibrationally excited molecule, toluene, and several bath gases. This was achieved by applying the method of kinetically controlled selective ionization (KCSI) (Paper I [J. Chem. Phys. 112, 4076 (2000), preceding article]). An optimum P(E′,E) representation is recommended (monoexponential with a parametric exponent in the argument) which uses only three parameters and features a smooth behavior of all parameters for the entire set of bath gases. In helium, argon, and CO2 the P(E′,E) show relatively increased amplitudes in the wings—large energy gaps |E′−E|—which can also be represented by a biexponential form. The fractional contribution of the second exponent in these biexponentials, which is directly related to the fraction of the so-called “supercollisions,” is found to be very small (<0.1%). For larger colliders the second term disappears completely and the wings of P(E′,E) have an even smaller amplitude than that provided by a monoexponential form. At such low levels, the second exponent is therefore of practically no relevance for the overall energy relaxation rate. All optimized P(E′,E) representations show a marked linear energetic dependence of the (weak) collision parameter α1(E), which also results in an (approximately) linear dependence of 〈ΔE〉 and of the square root of 〈ΔE2〉. The energy transfer parameters presented in this study form a new benchmark class in certainty and accuracy, e.g., with only 2%–7% uncertainty for our 〈ΔE〉 data below 25 000 cm−1. They should also form a reliable testground for future trajectory calculations and theories describing collisional energy transfer of polyatomic molecules.

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Section: Introductionmentioning

confidence: 99%

Collisional energy transfer probabilities of highly excited molecules from kinetically controlled selective ionization (KCSI). II. The collisional relaxation of toluene: P(E′,E) and moments of energy transfer for energies up to 50 000 cm−1

Lenzer

Luther

Reihs

et al. 2000

The Journal of Chemical Physics

108

156

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“…At higher kinetic energies, the up-step size becomes much larger, but the internal energy down-step size is almost independent of kinetic energy, and the net step size becomes positive; on average more energy is deposited in the internal degrees of freedom, the molecule is excited. Therefore the model indicates that the almost linear increase in the internal energy deposition, as found in many CID experiments [14,34,35], can be compatible with a down-step size which is almost independent of the collision temperature, as determined by experiments combined with modeling in thermal systems [19,20]. However, the model predicts such a dependence of the down-step size on kinetic energy only for relatively large up-step efficiencies Ͼ 0.2; for smaller efficiencies the magnitude of the down-step size also increases with kinetic energy.…”

Section: Results For Single Collisions (Non-steady State)mentioning

confidence: 94%

“…This dependence has been reproduced by a state-to-state statistical dynamical theory developed by Barker [7] and is used for the down-step side in most thermal energy transfer models [17,18]. Other approaches that could have been employed are a double exponential dependence [20] or a Gaussian dependence [1] of the probability density on the step size. Experiments and trajectory calculations have suggested a roughly linear dependence of the internal energy up-step size on the collision energy for some ion species [14,34,35], and an approximately square-root dependence for others [36,37].…”

Section: Theory and Implementationmentioning

confidence: 99%

“…This model also fails to yield realistic steady state distributions for the internal energy without additional arbitrary restrictions on the energy transfer. (2) Models have been developed to describe the collisional energy transfer in thermal unimolecular systems [1,4,5,17,18] and applied in particular to the collisional de-excitation of highly vibrationally excited molecules [19,20] and to resonance excitation experiments in RF ion traps [21]. However, they are suitable only for a steady state Maxwell distribution of collision energies.…”

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confidence: 99%

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A model for energy transfer in inelastic molecular collisions applicable at steady state or non-steady state and for an arbitrary distribution of collision energies

Plaß

Cooks

2003

J. Am. Soc. Mass Spectrom.

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A new model for energy exchange between translational and internal degrees of freedom in atom-molecule collisions has been developed. It is suitable for both steady state conditions (e.g., a large number of collisions with thermal kinetic energies) and non-steady state conditions with an arbitrary distribution of collision energies (e.g., single high-energy collisions). In particular, it does not require that the collision energies be characterized by a quasi-thermal distribution, but nevertheless it is capable of producing a Boltzmann distribution of internal energies with the correct internal temperature under quasi-thermal conditions. The energy exchange is described by a transfer probability density that depends on the initial relative kinetic energy, the internal energy of the molecule, and the amount of energy transferred. The probability density for collisions that lead to excitation is assumed to decrease exponentially with the amount of transferred energy. The probability density for de-excitation is obtained from microscopic reversibility. The model has been implemented in the ion trap simulation program ITSIM and coupled with an Rice-Rampsberger-Kassel-Marcus (RRKM) algorithm to describe the unimolecular dissociation of populations of ions. Monte Carlo simulations of collisional energy transfer are presented. The model is validated for non-steady state conditions and for steady state conditions, and the effect of the kinetic energy dependence of the collision cross-section on internal temperature is discussed. Applications of the model to the problem of chemical mass shifts in RF ion trap mass spectrometry are shown.

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“…It is rather of similar character to the "weak" collisional energy transfer observed for excited neutral molecules. [28][29][30][31][32] The results of Ref. 2 with the bath gas N 2 , extending over the temperature range 300-423 K and employing pressures up to 1 bar, have been evaluated previously in part I.…”

Section: Modeled Stabilization Fractionsmentioning

confidence: 99%

Electron attachment to POCl3. III. Measurement and kinetic modeling of branching fractions

Shuman

Miller

Viggiano

et al. 2011

The Journal of Chemical Physics

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Analysis by kinetic modeling of the temperature dependence of thermal electron attachment to CF3Br J. Chem. Phys. 137, 024303 (2012) Electron attachment to POCl 3 was studied in the bath gas He over the pressure range 0.4-3.1 Torr and the temperature range 300-1210 K. Branching fractions of POCl 3 − , POCl 2 − , Cl − , and Cl 2 − were measured. The results are analyzed by kinetic modeling, using electron attachment theory for the characterization of the nonthermal energy distribution of the excited POCl 3 −* anions formed and chemical activation-type unimolecular rate theory for the subsequent competition between collisional stabilization of POCl 3 −* and its dissociation to various dissociation products. Primary and secondary dissociations and/or thermal dissociations of the anions are identified. The measured branching fractions are found to be consistent with the modeling results based on molecular parameters obtained from quantum-chemical calculations.

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Temperature effects in the collisional deactivation of highly vibrationally excited pyrazine by unexcited pyrazine

Cited by 38 publications

References 41 publications

Collisional energy transfer probabilities of highly excited molecules from kinetically controlled selective ionization (KCSI). II. The collisional relaxation of toluene: P(E′,E) and moments of energy transfer for energies up to 50 000 cm−1

Collisional energy transfer probabilities of highly excited molecules from kinetically controlled selective ionization (KCSI). II. The collisional relaxation of toluene: P(E′,E) and moments of energy transfer for energies up to 50 000 cm−1

A model for energy transfer in inelastic molecular collisions applicable at steady state or non-steady state and for an arbitrary distribution of collision energies

Electron attachment to POCl3. III. Measurement and kinetic modeling of branching fractions

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