Scintillation process in three-component systems: mechanism of the luminescence minimum

Journal Article · Thu Apr 21 04:00:00 EDT 1988 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100319a031· OSTI ID:7004458

Yoshida, Y; Lipsky, S

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), Journal Name: J. Phys. Chem.; (United States) Vol. 92:8; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400500* -- Photochemistry
400600 -- Radiation Chemistry
ALKANES
ALKYLATED AROMATICS
AMINES
AROMATICS
AZOLES
BEAMS
BENZENE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BUTANE
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
CYCLOALKANES
CYCLOHEXANE
DATA
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ELECTRON BEAMS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
HEPTANE
HETEROCYCLIC COMPOUNDS
HOURS LIVING RADIOISOTOPES
HYDROCARBONS
INFORMATION
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KRYPTON 85
KRYPTON ISOTOPES
LEPTON BEAMS
LUMINESCENCE
MEASURING INSTRUMENTS
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXAZOLES
PARTICLE BEAMS
RADIATION CHEMISTRY
RADIATION DETECTORS
RADIATION EFFECTS
RADIATIONS
RADIOISOTOPES
RADIOLYSIS
SCINTILLATION COUNTERS
SCINTILLATIONS
TOLUENE
ULTRAVIOLET RADIATION
YEARS LIVING RADIOISOTOPES