Scintillation process in three-component systems: mechanism of the luminescence minimum
Three-component systems consisting of a saturated hydrocarbon solvent, C, an aromatic solvent, B, and a fluorescent solute, T, are excited either optically (in the absorption band of C and below its ionization potential) or with 0.67-MeV ..beta../sup -/ particles. The luminescence of T is detected and studied as a function of the B/C concentration ratio. Systems studied are C = cyclohexane, trans-decalin, methylcyclohexane, bicyclohexyl, n-heptane, or 2,3-dimethylbutane; B - benzene or toluene; and T = N,N,N',N'-tetramethylphenylenediamine (TMPD), p-terphenyl, or 2,5-diphenyloxazole (PPO). The luminescence behavior is observed under both aerated and nitrogenated conditions. For B = benzene, the luminescence of T is depressed by the replacement of C with B, at low B/C concentration ratios. This occurs for both modes of excitation for all C except bicyclohexyl and 2,3-dimethylbutane. At higher B/C concentration ratios, the luminescence of T recovers and ultimately exceeds its intensity in pure C + T. Thus there is observed a luminescence minimum. At low T concentrations the position and depth of the minimum are very sensitive to the presence of O/sub 2/, but at higher concentrations this sensitivity is lost. For B = toluene, the luminescence minimum is only observed under ..beta../sup -/ particle excitation conditions. A mechanism is developed to accommodate these observations. Its analysis indicates that production of S/sub 1/ states of B (i.e., B*) via either energy transfer from C* or via charge transfer from C/sup +/ followed by the geminate recombination B/sup +/ + e/sup -/ ..-->.. B* is intrinsically inefficient in dilute cyclohexane solutions. For B = benzene this inefficiency resides mainly in the electronic energy transfer process and for toluene in the ion-recombination process. Also, the analysis indicates that there must be two states of C that can transfer energy to B and/or T.
- Research Organization:
- Univ. of Minnesota, Minneapolis (USA)
- OSTI ID:
- 7004458
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 92:8
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
AMINES
LUMINESCENCE
RADIOLYSIS
SCINTILLATIONS
BENZENE
BUTANE
CYCLOHEXANE
HEPTANE
OXAZOLES
TOLUENE
ELECTRON BEAMS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXPERIMENTAL DATA
KRYPTON 85
SCINTILLATION COUNTERS
ULTRAVIOLET RADIATION
ALKANES
ALKYLATED AROMATICS
AROMATICS
AZOLES
BEAMS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
CYCLOALKANES
DATA
DECOMPOSITION
ELECTROMAGNETIC RADIATION
EVEN-ODD NUCLEI
HETEROCYCLIC COMPOUNDS
HOURS LIVING RADIOISOTOPES
HYDROCARBONS
INFORMATION
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KRYPTON ISOTOPES
LEPTON BEAMS
MEASURING INSTRUMENTS
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PARTICLE BEAMS
RADIATION CHEMISTRY
RADIATION DETECTORS
RADIATION EFFECTS
RADIATIONS
RADIOISOTOPES
YEARS LIVING RADIOISOTOPES
400500* - Photochemistry
400600 - Radiation Chemistry