Photophysical Processes in the Gas Phase at High Levels of Vibrational Excitation of Triplet Molecules of Benzophenone and Fluorenone |
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Authors: | G A Zalesskaya D L Yakovlev E G Sambor D V Prikhodchenko |
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Institution: | (1) Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70 F. Skorina Ave., Minsk, 220072, Belarus |
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Abstract: | By the delayed fluorescence activated by direct multiphoton excitation of triplet molecules by CO2–laser radiation we have studied the prevailing deactivation pathways of triplet molecules with a high store of vibrational energy E
vib. The dependences of the kinetic characteristics of delayed fluorescence on the presence of vapors and foreign gases have been used to estimate the rates and efficiencies of intermolecular vibrational relaxation in the vibrational quasi–continuum of the triplet state T
1. By the changes in the intensities and decay rates over a wide range of vibrational energies we have established the E
vib dependences of reversible intercombination conversion between the states T
1 and S
1 and interconversion from T
1 to the ground electronic state S
0 for both the case of isolated excited molecules and at a steady vibrational temperature. It is shown that at high vibrational temperatures the radiationless transition from the T
1 state to S
0 has an activation character and is accomplished through the energy barrier. The conditions for going to an exponential dependence have been determined. It has been found that the obtained dependences are in good agreement with the known experimental results. The influence of molecular and environmental characteristics on the decay rate of triplet molecules is compared. |
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Keywords: | delayed fluorescence radiation processes vibrational excitation polyatomic molecules |
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