Time resolved measurement of CF2 formation in the infrared multiphoton dissociation of CF2HCl

Duperrex, R.; Bergh, Hubert van den

doi:10.1063/1.438820

Cited by 55 publications

(9 citation statements)

References 25 publications

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“…The parameter h 10 , which accounts for the contribution from the pressure independent dissociation of CF 2 HCl, takes on small values for both fluences. Even at the lowest initial concentration, P 0 = 0.2 mbar, h 10 is smaller than the fraction of molecules dissociated per pulse (Figure ), f , which is defined by 4 This result indicates that collisional effects provide a significant contribution to the final observed yield, even within fluence and pressure ranges for which some authors claim that the MPD of CF 2 HCl is collisionless. The importance of the laser beam fluence in the weakening of the anharmonic barrier is also shown by the fact that h 10 increases up to four times its original value when the fluence is doubled.…”

Section: Resultsmentioning

confidence: 91%

Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

Torresano

Santos

1996

J. Phys. Chem.

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An extension of the method of McRae et al. is proposed to quantify the contribution of the distinct collisional processes to the total yield obtained in infrared multiphoton dissociation experiments. The extension consists of the introduction of a substrate pressure dependence in the parameter representing one homogeneous collision. This allows the application of the method at a pressure where the collision time is of the order of the temporal width of the laser pulse and the discrimination between the different processes associated in a given collisional sequence. We have tested the reliability of this extended method by applying it to the multiphoton dissociation of CF 2 HCl, where the dependence of the dissociation yield on initial pressure and laser fluence has been investigated. We have shown that the homogeneous collisions occurring during the laser pulse may play a fundamental role in the weakening of the bottleneck absorption effects. It has been also suggested that fluence is the main excitation parameter for fixing the pressure interval along which dissociation can be regarded as collisionless.

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Section: Resultsmentioning

confidence: 91%

Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

Torresano

Santos

1996

J. Phys. Chem.

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“…We consider these results indicative but only semiquantitative. Deviations of up to 10% in λ max have been reported for a large number of small- to medium-sized molecules. , For example, the experimental data for CF 2 from refs − led to λ max = 248 nm and f = 0.024–0.034 (see refs , , , , and ) in comparison with the theoretical values given above. One complication arises from the possibility that higher electronic transitions at high temperatures may extend their absorptions to longer wavelengths.…”

Section: Quantum-chemical Characterization Of Absorption Spectramentioning

confidence: 77%

Kinetic and Spectroscopic Studies of the Reaction of CF₂ with H₂ in Shock Waves

et al. 2017

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The reaction of CF with H was studied in shock waves by monitoring UV absorption signals. CF was prepared by thermal dissociation of CF (or of c-CF). The rate constant of the reaction CF + H → CHF + HF near 2000 K was found to be close to 10 cm mol s, consistent with earlier information on the reverse reaction CHF + HF → CF + H and a modeled equilibrium constant. The kinetic studies were accompanied by spectroscopic investigations. Absorption cross sections of CF between 190 and 220 nm were measured near 1000 K and compared with room-temperature values from the literature. Likewise, absorption cross sections of CF near 2000 K were measured between 210 and 300 nm and compared with room-temperature data. Additional superimposed absorption signals were recorded during the reaction and identified by their time dependence and by quantum-chemical calculations employing time-dependent density functional theory. A previously unknown absorption spectrum of CHF radicals near 200 nm was identified and its wavelength dependence determined. Further strong absorptions between 190 and 300 nm were attributed to CHF and CF radicals. Absorptions at longer wavelengths, reaching up to 510 nm, were postulated to arise from C radicals formed at later stages of the reaction.

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“…As an alternative to model calculations, the approximate method outlined by Quack may be used. 3 (d),3(e) In the method described by Quack, the steady -state system of differential equations can be solved to give -In(1 -F) = k.(I) rp , (9) where ka(I) is an intensity-dependent phenomenological rate constant for depletion of the reactant; F is either F p or F T, as defined ear lier . A plot of -In( 1 -F) vs rp should give a straight line of slope k(I) and zero intercept.…”

Section: Steady-state Systemsmentioning

confidence: 99%

IR photochemistry: A unified approach for single-channel reactions. II. Treatment of experimental data

Baldwin

Barker

1981

The Journal of Chemical Physics

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IR photochemistry: A unified approach for singlechannel reactions. I. Theory and computational examplesIn the preceding paper of this series [I. Chern. Phys. 74,3813 (1981)], it was shown that multiphoton decomposition yields versus fluence or time can be expressed as cumulative log-normal distribution functions (CLNDF). In the present paper, this idea is exploited for the purpose of presenting and analyzing experimental data. Such data from several different laboratories are used to show the effects of convolution of the laser spatial profile. Also shown are examples of homogeneous behavior, "active/inactive" population subsets, and more general cases. This approach permits a unified description of the experimental system, regardless of the potential complexities.

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Time resolved measurement of CF2 formation in the infrared multiphoton dissociation of CF2HCl

Cited by 55 publications

References 25 publications

Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

Kinetic and Spectroscopic Studies of the Reaction of CF₂ with H₂ in Shock Waves

IR photochemistry: A unified approach for single-channel reactions. II. Treatment of experimental data

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Time resolved measurement of CF2 formation in the infrared multiphoton dissociation of CF2HCl

Cited by 55 publications

References 25 publications

Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

Kinetic and Spectroscopic Studies of the Reaction of CF2 with H2 in Shock Waves

IR photochemistry: A unified approach for single-channel reactions. II. Treatment of experimental data

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Kinetic and Spectroscopic Studies of the Reaction of CF₂ with H₂ in Shock Waves