The contribution of electronically excited states to the radiation chemistry of organic systems. Progress report, January 1, 1991--April 30, 1992
At low concentrations ({le}10{sup {minus}3}M) of aromatic solutes in saturated. hydrocarbon solvents, very efficient transport of electronic energy from photo-excited solvent to aromatic is observed. Effects of temperature, dilution, and quenching additives are being studied. Two-photon pulsed laser excitation gives no evidence of long lived metastable states. The fluorescence quantum yields of saturated hydrocarbon liquids have been studied for excitation wavelengths from 200 to 120 nm. For many compounds, the quantum yields for fluorescence are observed to decline to a minimum value at, or near, previously reported ionization thresholds. At higher energies, the magnitude of the quantum yield for fluorescence begins to increase. Magnetic field effects on intensity of steady-state recombination fluorescence have been observed both for photo-generated and {Beta}{sup {minus}} generated, electron and positive ion geminate pairs in saturated hydrocarbon liquids. The comparison indicates an important contribution . to observed recombination fluorescence from multiple ion-pairs under radiation chemical conditions. For photo-excited aromatic solutes dissolved in saturated hydrocarbon liquids, no magnetic field effect could be observed until surprisingly large excess energies above the threshold for ionization were achieved. This suggests a much smaller average range for the thermalized electron than expected from photoconductivity.
- Research Organization:
- Minnesota Univ., Minneapolis, MN (United States). Dept. of Chemistry
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-85ER13404
- OSTI ID:
- 10182070
- Report Number(s):
- DOE/ER/13404-7; ON: DE92040465
- Resource Relation:
- Other Information: PBD: [1992]
- Country of Publication:
- United States
- Language:
- English
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