Bimolecular Ionization of the Triplet State of Aromatic Hydrocarbons in Solution

1968 ◽  
Vol 49 (4) ◽  
pp. 1577-1587 ◽  
Author(s):  
L. P. Gary ◽  
Klaas de Groot ◽  
R. C. Jarnagin
Keyword(s):  
Triplet State ◽  
Aromatic Hydrocarbons

The polymerization of styrene sensitized by molecules in the triplet state II. Kinetics and mechanism

1959 ◽  
Vol 251 (1264) ◽  
pp. 4-26 ◽  
Keyword(s):  
Triplet State ◽  
Aromatic Hydrocarbons ◽  
Flash Photolysis ◽  
Radical Addition ◽  
Photochemical Reactions ◽  
Kinetics And Mechanism ◽  
Qualitative Investigation ◽  
Initiation Mechanism ◽  
Initial Formation ◽  
Mechanism Of The Reaction

The kinetics and mechanism of the reaction between anthracene and styrene have been fully investigated. By means of flash photolysis techniques, it has been confirmed that it is the triplet state of anthracene which sensitizes the polymerization. It has also been shown that both triplet and unexcited singlet anthracene copolymerize with styrene, the former with a zero activation energy. The work has been extended to the polymerizations sensitized by pyrene and chrysene, and to the unsensitized photopolymerization of styrene. It has been shown that in every case an initiation mechanism, involving the initial formation of a triplet-monomer complex, satisfactorily explains the observed results. The copolymerization rates of pyrene and chrysene were undetectable; these results, coupled with those obtained for the copolymerization of anthracene with styrene, are in agreement with the conclusions of Kooyman & Farenhorst, Szwarc, and others, concerning the reactivity of olefinic and aromatic hydrocarbons to radical addition. Finally, a qualitative investigation of the photochemical reactions between the sensitizers, and cumene and 9 .10-dihydroanthracene, has been made.

Triplet state formation efficiencies of aromatic hydrocarbons in solution

1968 ◽  
Vol 306 (1485) ◽  
pp. 257-273 ◽  
Keyword(s):  
Triplet State ◽  
State Formation ◽  
Aromatic Hydrocarbons ◽  
Rate Constants ◽  
Internal Conversion ◽  
Transition Probability ◽  
Radiative Transition ◽  
Excited Singlet ◽  
Radiative Transitions ◽  
Solvent Systems

The triplet state formation efficiencies,ф T , of ten aromatic hydrocarbons have been deter­mined in ethanol and, in some cases, in other solvents. Fluorescence yields, ф F , for the various hydrocarbon-solvent systems were measured where literature values were not available. With the exception of coronene the sum of ф F + ф T was found to be unity within experi­mental error, which indicates little or no internal conversion from the first excited singlet state of each hydrocarbon. Rate constants for intersystem crossing, k IS and the ratio k IS / k F , where k F is the radiative transition probability, have been calculated for each hydrocarbon in ethanol. The ratio varies much less than do the separate rate constants and the significance of this is discussed in terms of possible selection rules for spin forbidden non-radiative transitions.

The radiation-induced formation of excited states of aromatic hydrocarbons in benzene and cyclohexane. III. Effect of singlet state quenchers

1972 ◽  
Vol 328 (1575) ◽  
pp. 481-496 ◽  
Keyword(s):  
Triplet State ◽  
Excited States ◽  
State Formation ◽  
Aromatic Hydrocarbons ◽  
Extinction Coefficient ◽  
Singlet State ◽  
Excited Singlet State ◽  
Intersystem Crossing ◽  
Excited Singlet ◽  
Radiation Induced

The contribution to naphthalene and pyrene triplet state formation of intersystem crossing from the excited singlet state has been determined for both cyclohexane and benzene solutions using the singlet state quenchers nitromethane and xenon. In agreement with the conclusions reported in part II, intersystem crossing plays an important role; under certain conditions up to 50 % of the total triplet yield in naphthalene-cyclohexane solutions has this origin. The extinction coefficient for naphthalene triplet absorption in cyclohexane at λ max = 412.5 nm is 20 000 ± 5000 1 mol -1 cm -1 .

Sign in / Sign up

Export Citation Format

Share Document