A study of the excited electronic states of 9-fluorenone |
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Authors: | R Zwarich A Bree |
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Institution: | Chemistry Department, State University of New York at Albany, Albany, New York 12222 USA;Chemistry Department, University of British Columbia, Vancouver 8, B. C., Canada |
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Abstract: | Some spectroscopic properties of the low-energy electronic states of 9-fluorenone have been examined. The spectra in paraffin matrices at 4.2°K show detailed vibrational spectra. Two fluorescence spectra are observed; a diffuse emission arises from 9-fluorenone crystals in the paraffin matrix, and a sharp emission is characteristic of the molecule. The sharp fluorescence is analyzed in terms of known a1 vibrational fundamentals. The sharp absorption is a near mirror-image to the fluorescence, so Herzberg-Teller vibrations are not prominent. The polarization in the crystal spectrum allows this low-energy transition near 23 000 cm?1 to be assigned . Because there is no vibronic perturbation in fluorescence, and certainly no out-of-plane modes, a transition seen at about 26 000 cm?1 is tentatively assigned . Another sharp absorption system is seen at 31 000 cm?1 in the paraffin matrices at 4.2°K (linewidth 6 cm?1) but no fluorescence was detected. The polarized crystal spectrum indicated the assignment of this system and another very strong system at 40 000 cm?1 to be , while other systems at about 34 000 cm?1 and 44 000 cm?1 are .The phosphorescence spectrum of pyrene-d10 held in a single crystal of 9-fluorenone at 4.2°K has been recorded. No delayed fluorescence from the host crystal is observed at 4.2°K but is intense at 77°K. The energy difference between host and guest triplet levels is estimated to be about 900 cm?1 allowing the lowest triplet state of 9-fluorenone to be placed at 17 800 cm?1. |
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