Pulsed CO2 laser induced multiphoton decomposition of cyclobutanone: A comparison of predictions for three models of decomposition probability vs. fluence

Nicol, Gordon; Evans, Douglas E.; McAlpine, Robert D.

doi:10.1007/bf00695589

Cited by 15 publications

(4 citation statements)

References 23 publications

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“…These either represent the yield by averaging over all the pulses used in the irradiation (e.g. the fraction of molecules dissociated per laser pulse, f , or the reaction volume, V R ) or take the number of pulses as a continuous temporal variable and derive kinetic equations to represent the dissociation process. , Problems with these procedures have already been pointed out elsewhere . Actually dissociation products may significantly affect the subsequent excitation process through their collisions with parent molecules.…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

Torresano

Santos

1996

J. Phys. Chem.

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“…7. These results were modeled with (8), which results from integrating (6) with the probability of dissociation per pulse defined in (4) and the fluence distribution described in (2) Fig. 7 Fluence dependence of the effective volume of dissociation.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, deconvolution procedures must be used to obtain the fluence dependence of the dissociation probability. Several deconvolution models have been proposed [4][5][6][7][8][9][10][11][12]. However, a two-parameter model based on the cumulative log-normal distribution has demonstrated to satisfactorily describe the dissociation probabilities of molecules over a wide fluence range in IRMPD [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Direct determination of the dissociation probability in highly focused IR multiple photon dissociation

et al. 2011

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Laser-induced fluorescence (LIF) has been used to directly determine the dissociation probability per pulse in highly focused infrared multiple-photon dissociation (IRMPD). The fluence dependence of CDCl 3 IRMPD has been determined by LIF and FTIR spectrometry. The particular LIF irradiation and detection system's geometry implemented allowed us to monitor the local CCl 2 radicals concentration in the intersection zone of the observation and the dissociation volumes. The fluence dependence of the LIF intensity was modeled with the cumulative log-normal distribution. The dependence of the global values of the fraction of molecules dissociated per pulse on fluence was obtained from FTIR spectrometry. The dissociation probabilities per pulse were derived from the deconvolution of these values using the cumulative log-normal distribution. A very good agreement between the values of the parameters σ and Φ sat obtained from the deconvolution technique with those resulting from the fluorescence intensity fit was found, showing the validity of the method proposed.

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“…These are not available, and an average 7 was used in the least -squares fit of relation (10) to the low pressure CF3Br data, yielding (with Fthr = 0.25 J /pulse) : w13(13CF3Br, 0.10 torr) = (3.6 ± 0.8) x 10-4 x exp [-0.25/(0.14 ± 0.01) E ] (16) u13(13CF3Rr, 0.25 torr) = (3.2 ± 0.5) x 10-4 x exp [-0.25/(0.17 ± 0.01) E ] (17) Relations (16) and (17) are shown as full and dashed lines, resp., on fig. 8.…”

Section: Dissociation Probabilitiesmentioning

confidence: 99%

Multiphoton Dissociation Of CP 3 C1 And CF 3 Br Under CO 2 Laser Pulses

Mévergnies¹

1986

SPIE Proceedings

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Multiphoton dissociation of CP3C1 and CF3Br induced by CO2 laser pulses has been studied in the (0.1 -60 torr) pressure range and (5 -30 Joule /cm2) average energy density rance. The laser was adjusted on 1071.9 cm -1 and 1052.2 cm -1, resp., so as to excite preferentially the 13C isotopic molecules.The effects of pressure and energy on the isotopic selectivity were measured and a remarkable difference was found between the two molecules. As for the dissociation probabilities, they vary exponentially with the inverse of the energy. The applicability of such an Arrhenius -type relation is discussed and semi -quantitatively justified.* preliminary results on CF3C1 were presented at the 90 Int. AbstractMultiphoton dissociation of CF 3 C1 and CF^Rr induced by CO2 laser pulses has been studied in the (0.1 -60 torr) pressure ranqe and (5 -30 Joule/cm2 ) averaae enerqy density ranae. The laser was adjusted on 1071.9 cm"" 1 and 1052.2 cm" 1 , resp., so as to excite preferentially the 13 C isotopic molecules.The effects of pressure and energy on the isotopic selectivity were measured and a remarkable difference was found between the two molecules. As for the dissociation probabilities, they vary exponentially with the inverse of the enerqy. The applicability of such an Arrhenius-type relation is discussed and semi-quantitatively justified.

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Pulsed CO2 laser induced multiphoton decomposition of cyclobutanone: A comparison of predictions for three models of decomposition probability vs. fluence

Cited by 15 publications

References 23 publications

Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

Direct determination of the dissociation probability in highly focused IR multiple photon dissociation

Multiphoton Dissociation Of CP 3 C1 And CF 3 Br Under CO 2 Laser Pulses

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