Vibronic Structures of the Ground and Excited Singlet Electronic States of Dimethylnaphthalenes Cooled in a Supersonic Jet

Borisevich, N. A.; Vodovatov, L. B.; D'yachenko, G. G.; Petukhov, V. A.; Semenov, M. A.

doi:10.1080/00387019708001636

Cited by 5 publications

(2 citation statements)

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“…The fluorescence emission spectra obtained after the excitation of the origin of the transition S 2 rS 0 around 321 nm are shown in Figure 3 in comparison with the one measured by Numata et al 42 As expected, the excitation from S 0 to S 2 generates an emission fluorescence spectrum characterized by the presence of several vibronic bands with distinguishable broad band structures. These fluorescence emission spectra are found in good agreement with those issued from the literature, 38,42,43 whatever the concentration or the conditions of gaseous environment of the pyrene. As for the excitation spectra, we also note a slightly less structured and noisier shape, due to the less efficient cooling of our setup and above all the low concentrations of pyrene under flame conditions compared to the spectrum (Figure 3a) issued from the literature.…”

Section: ' Experimental Setupsupporting

confidence: 88%

“…This choice maximizes thus the sensitivity of the method but partly to the detriment of its spectral selectivity, the emission spectrum of fluorescence for a S 2 excitation leading indeed to a diffuse spectrum with less resolved structures compared to the fluorescence spectrum provided by a S 1 excitation. This point is clearly highlighted in the work of Borisevich et al where the structure of the fluorescence spectrum of pyrene after a S 2 ←S 0 excitation is shown to be wider and structureless than for a S 1 ←S 0 excitation. The reason of that loss of structure is mainly due to the large excess of energy involved for a S 2 excitation which implies a stronger contribution of nonradiative processes such as internal conversion (IC), intersystem crossing (ISC), and intravibrational redistribution (IVR).…”

Section: Methodsmentioning

confidence: 84%

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Pyrene Measurements in Sooting Low Pressure Methane Flames by Jet-Cooled Laser-Induced Fluorescence

et al. 2011

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This paper presents in detail the study we carried out concerning the pyrene measurement by jet-cooled laser-induced fluorescence (JCLIF) in different sooting low pressure methane flames. The aim of this paper is both to demonstrate the potentialities of this technique for the measurement of such moderately sized polycyclic aromatic hydrocarbons under sooting flame conditions and to provide new experimental data for the understanding and the development of chemical models of the soot formation processes. Several concentration profiles of pyrene measured in different sooting flame (various pressure and equivalence ratio) are presented. The validation of the JCLIF method for pyrene measurements is explained in detail as well as the calibration procedure, based on the standard addition method, which has been implemented for the quantification of the concentration profiles. Sensitivity lower than 1 ppb was obtained for the measurement of this species under sooting flame conditions.

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Section: ' Experimental Setupsupporting

confidence: 88%

Section: Methodsmentioning

confidence: 84%

Pyrene Measurements in Sooting Low Pressure Methane Flames by Jet-Cooled Laser-Induced Fluorescence

et al. 2011

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Comparative analysis of high-resolution spectra of naphthalene and its methyl-substituted derivatives cooled in a supersonic jet

2007

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We have carried out a comparative analysis of fine-structure fluorescence excitation and fluorescence spectra of naphthalene, 2,6-and 2,7-dimethylnaphthalene, and 2-methylnaphthalene molecules cooled in a supersonic jet. We have shown that both the frequencies and the intensities of most of the lines in the spectra of these molecules are correlated. Such a correlation facilitates interpretation of the spectra in the case when it is difficult to calculate the transition intensities and when lines corresponding to vibrations of different symmetry have close frequencies. For the considered molecules, a preliminary assignment of the lines in the fine-structure spectra is refined.Introduction. Fine-structure spectra of complex molecules obtained in a supersonic jet allow us to determine with high accuracy the frequencies of optically active vibrations in the electronic ground state and electronic excited states and the intensities of the corresponding vibronic transitions. Due to high characteristicity, such spectra are an important source of information for constructing theoretical models of the molecules and can be the basis for developing methods for identification of chemical compounds. But assignment of the lines in the measured spectra for complex molecules is not a simple problem and cannot always be solved correctly. So in the literature, we often encounter different or incomplete interpretations of the spectra for the same molecules. For interpretation of the fine-structure spectra, along with the calculations we need to draw on additional experimental data. In fact, the accuracy of the calculation of the vibrational frequencies (≈20 cm -1 ) available today does not allow us to distinguish lines with close frequencies. Calculation of the transition intensities could make this problem significantly easier to solve. However, to date there have been no satisfactory methods for calculating the transition intensities: the calculated values may differ from the experimental values by an order of magnitude or more. Such errors arise first of all due to the fact that for calculating the transition intensities, we need to more accurately know the geometry in the ground state and the excited states. This is connected with the fact that perturbations of the force field affect the intensities to first order in perturbation theory, while they affect the vibrational frequencies only to second order. Secondly, calculation of the intensities can be carried out in various approximations. In the Franck-Condon approximation, we can calculate the transition intensities only between totally symmetric vibrational states. For the more exact Herzberg-Teller approximation, we need additional vibronic coupling parameters, calculation of which is made more complicated by the need to solve the vibronic problem. In such a case, we need to know how to extract as much information as possible from the experimental data. For example, the problem can be made easier by simultaneous analysis of spectra of structurally similar molecules. Thus in ...

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Experimental measurement and calculation of the line intensities in vibronic spectra of jet-cooled anthracene

et al. 2000

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Vibronic Structures of the Ground and Excited Singlet Electronic States of Dimethylnaphthalenes Cooled in a Supersonic Jet

Cited by 5 publications

References 10 publications

Pyrene Measurements in Sooting Low Pressure Methane Flames by Jet-Cooled Laser-Induced Fluorescence

Pyrene Measurements in Sooting Low Pressure Methane Flames by Jet-Cooled Laser-Induced Fluorescence

Comparative analysis of high-resolution spectra of naphthalene and its methyl-substituted derivatives cooled in a supersonic jet

Experimental measurement and calculation of the line intensities in vibronic spectra of jet-cooled anthracene

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