Deviations from Lindemann behaviour: photoisomerization dynamics of trans-stilbene under collisional gas phase conditions

Meyer, A.; Schroeder, J.; Troe, J.; Votsmeier, Martin

doi:10.1016/s1010-6030(96)04542-x

Cited by 9 publications

(13 citation statements)

References 47 publications

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“…In another approach to experimentally determine the high pressure limit of the photoisomerization rate coefficient of trans-4, we presently measure its fluorescence decay in thermal vapor and with added buffer gas, again in the single photon counting set-up described above using a suitable sample cell [49,76]. First preliminary experiments indicate that in thermal trans-4 vapor under collision free conditions the decay consists of two components: a dominant fast one contributing about 95 percent to the signal amplitude that may be characterized by a lifetime of 47 ps, and a slow component whose time constant is about 10 times as large.…”

Section: Discussionmentioning

confidence: 99%

Fluorescence Excitation Spectrum, Lifetimes and Photoisomerization of Jet-Cooled Conformers of 1,1´-bi(benzocyclobutylidene)

Ernst¹,

Rupp²,

Frank³

et al. 2002

Zeitschrift Für Physikalische Chemie

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Fluorescence Excitation Spectra / 1,1 -bi(benzocyclobutylidene) / PhotoisomerizationFirst measurements of fluorescence excitation spectra of the recently synthesized rigid stilbene analogue 1,1 -bi(benzocyclobutylidene) in a supersonic jet expansion show that, in contrast to the parent compound, both the trans-and the cis-conformer fluoresce under these conditions. The excitation energy dependence of fluorescence lifetimes indicates the onset of an efficient non-radiative decay channel above energy thresholds of 1340 cm −1 and 990 cm −1 for the trans-and cis-form, respectively, which is assigned to photoisomerization in the singlet state. From an RRKM analysis of the microcanonical rate coefficients an estimate of the high pressure limit of the thermal photoisomerization rate coefficient is obtained and compared with photoisomerization rate coefficients measured in low viscosity solution and in thermal vapor. There are strong indications that for this compound there are no dynamic or static solvent induced effects that lead to an anomalous acceleration of the reaction in solution.

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Section: Discussionmentioning

confidence: 99%

Fluorescence Excitation Spectrum, Lifetimes and Photoisomerization of Jet-Cooled Conformers of 1,1´-bi(benzocyclobutylidene)

Ernst¹,

Rupp²,

Frank³

et al. 2002

Zeitschrift Für Physikalische Chemie

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“…Fluorescence decays of trans -stilbene after laser excitation at 310.4 nm were measured with a standard single photon counting system described in more detail elsewhere. , Stilbene crystals were introduced into the heated stainless steel sample cell shown in Figure such that the concentration was determined by the vapor pressure of stilbene of about 10 μbar. The cell could be evacuated to pressures below 50 μbar, and its temperature was controlled to within 0.5 °C between 20 °C and 100 °C.…”

Section: Methodsmentioning

confidence: 99%

“…This is the falloff regime of the unimolecular photoisomerization reaction of trans-stilbene in the S 1 state and it is located well below the densities of the so-called Kramers turnover region which was investigated in great detail in the past. 14,18,[28][29][30][31][32] Whereas determinations of microcanonical rate coefficients k(E) from supersonic jets, 21,23,24,[33][34][35][36] fluorescence decay measurements under thermal collision-free conditions, [37][38][39][40] and studies of the density dependence of the photoisomerization rate coefficients at bath gas pressures above 5-10 bar in different solvents are available, 18,28,29,31,35,41 systematic studies at lower pressure are scarce. 39,40 As one may expect to find essential clues to the discussed problem in this density regime, we investigated trans-stilbene fluorescence decays in a variety of fluid solvents in the relevant pressure range in great detail.…”

Section: Introductionmentioning

confidence: 99%

“…14,18,[28][29][30][31][32] Whereas determinations of microcanonical rate coefficients k(E) from supersonic jets, 21,23,24,[33][34][35][36] fluorescence decay measurements under thermal collision-free conditions, [37][38][39][40] and studies of the density dependence of the photoisomerization rate coefficients at bath gas pressures above 5-10 bar in different solvents are available, 18,28,29,31,35,41 systematic studies at lower pressure are scarce. 39,40 As one may expect to find essential clues to the discussed problem in this density regime, we investigated trans-stilbene fluorescence decays in a variety of fluid solvents in the relevant pressure range in great detail. The analysis of the observed decays required a complete master equation simulation, taking into account the details of collisional energy transfer to the solvent environment.…”

Section: Introductionmentioning

confidence: 99%

“…The analysis of the observed decays required a complete master equation simulation, taking into account the details of collisional energy transfer to the solvent environment. 40…”

Section: Introductionmentioning

confidence: 99%

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Photoisomerization of trans-Stilbene in Moderately Compressed Gases: Pressure-Dependent Effective Barriers

1999

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A systematic experimental study of the bath gas and pressure dependence of the photoisomerization of transstilbene in the low to intermediate pressure regime is presented. The analysis of the results by a detailed numerical master equation simulation reveals specific bath gas influences in the effective specific rate constants for isomerization that are already observable at pressures of about 1 bar. The low-pressure regime of the unimolecular reaction in the S 1 state can be located in the pressure range well below 1 bar for most of the bath gases. The effective "high-pressure limit" of the photoisomerization rate constant that can be extracted from the simulation is found to be pressure dependent, approaching a bath gas specific plateau value in the 10 bar range for bath gases such as methane, ethane, propane, or xenon. The existence of a bath gas dependent plateau of the effective high-pressure limit is consistent with the proposition of a pressure-or density-dependent effective barrier of the reaction. The values obtained for the pressure-dependent barrier height agree with the trend observed in earlier experiments in highly compressed gases and liquids and confirm a substantial contribution of "static" lowering of the reaction barrier. Additional "dynamic" lowering of the effectice barrier due to collision-induced intramolecular vibrational energy redistribution cannot be ruled out, however, and the relative importance of these two contributions remains an open question. The recently proposed effect of vibrational Franck-Condon cooling upon optical excitation of trans-stilbene definitely is not consistent with the experimental results.

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Ab initio CI study on electronically excited stilbene

Amatatsu

1999

Journal of Molecular Structure: THEOCHEM

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Deviations from Lindemann behaviour: photoisomerization dynamics of trans-stilbene under collisional gas phase conditions

Cited by 9 publications

References 47 publications

Fluorescence Excitation Spectrum, Lifetimes and Photoisomerization of Jet-Cooled Conformers of 1,1´-bi(benzocyclobutylidene)

Fluorescence Excitation Spectrum, Lifetimes and Photoisomerization of Jet-Cooled Conformers of 1,1´-bi(benzocyclobutylidene)

Photoisomerization of trans-Stilbene in Moderately Compressed Gases: Pressure-Dependent Effective Barriers

Ab initio CI study on electronically excited stilbene

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