WorldCat Identities

Kropp, John L.

Overview
Works: 7 works in 9 publications in 1 language and 9 library holdings
Roles: Author
Publication Timeline
.
Most widely held works by John L Kropp
Triplet to triplet absorption in organic molecules for use in photochromic devices by J.L Kropp( Book )

3 editions published between 1968 and 1971 in English and held by 3 WorldCat member libraries worldwide

The photochromic properties of several substituted aromatics and heterocyclics have been investigated. The absorption spectra, phosphorescence lifetime T-T absorption spectra and the product of triplet extinction coefficient and triplet formation efficiency, were evaluated for representative compounds. Using these data the photochromic properties of heterocyclics are compared to their hydrocarbon analogs. The values of the maximum triplet formation efficiency are lower for heterocyclics than for aromatics. However, broader T-T absorption and more efficient absorption for pumping light suggest that, on balance, heterocyclics are comparable to aromatic hydrocarbons in their effectiveness as photochromic materials. The variation of solvent induces large changes in the photochromic properties of heterocyclics thus providing a useful additional parameter for adjusting their properties. These differences also promise to shed light on the mechanism of radiationless transitions in these compounds. Recommendations for further studies to improve the photochromic properties of heterocyclics are made. (Author)
Radiationless deactivation and anomalous fluorescence of singlet 1,12 benzperylene( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

Values of the rate constants for processes that deactivate the lowest excited singlet state of 1,12 benzperylene were determined between -196C and 23C from measurements of the quantum yields of triplet formation, fluorescence, and the fluorescence lifetime. The rate constant for intersystem crossing to the triplet state is nearly same at -196C and +23C. The rate constant for direct radiationless deactivation to the lowest singlet is probably zero at -196C but increases to 600000/sec at +23C. This is similar to results obtained for other aromatic hydrocarbons. However, the fluorescence of 1,12 benzperylene is atypical. An increase in the rate constant of fluorescence, k1, from -196C to +23C is observed resulting from an increase in fluorescence with temperature while fluorescence lifetime decreases over the same temperature range. The increase in k1 with increasing temperature is attributed to a temperature dependent emission from the second excited singlet state. Since the second excited singlet state of 1,12 benzperylene lies only 1275 to 1400/cm above the (1)Lb state, there is significant thermal population of the (1)La state of +23C. The observation of a temperature dependent anti stokes fluorescence supports this interpretation. The effect of solvent upon the energy gap between the (1)La and (1)Lb state and the fluorescence properties of 1,12 benzperylene is discussed. (Author)
The Temperature Dependence of Ovalene Fluorescence( Book )

1 edition published in 1970 in English and held by 1 WorldCat member library worldwide

The fluorescence yield, the fluorescence lifetime, and the changes in fluorescence spectrum of ovalene were measured at temperatures ranging from -196 to 50C in various solvents and plastic matrices. (Author)
Fluorescence and phosphorescence of aromatic hydrocarbons in poly(methylmethacrylate) as a function of temperature( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

Fluorescence lifetimes (t) and fluorescence yields(P) of poly(methylmethacrylate) samples containing coronene-h12, coronene-d12, pyrene-h10, pyrene-d10, 1,2;5,6 dibenzanthracene, 1,2;7,8 dibenzanthracene, 1,2;3,4 dibenzanthracene, 1,2 benzcoronene and 1,12 benzperylene were measured. For all compounds studied, except coronene-h12 and coronene-d12, t decreases with increasing temperature. For all compounds except 1,12 benzperylene and 1,2;3,4 dibenzanthracene, P decreases proportionally with t so that the radiative lifetime (t) is temperature independent. For the two last mentioned compounds t varies with temperature. This may be due to the closeness of the p band to the lowest-lying alpha band. The activation energies of temperature dependent quenching of t are all similar. The quenching is related to Lin's theory of radiationless transitions and it is suggested that this temperature dependent quenching is due to S1 -- So transitions. (Author)
Effect of Propanol upon the Absorption and Emission of Benzquinolines in 3 Methyl Pentane( Book )

1 edition published in 1970 in English and held by 1 WorldCat member library worldwide

The authors report the variation of fluorescence, phosphorescence and of T-T absorption intensities as propanol is added to a 3-methylpentane (MP) solutions of benzoquinolines. (Author)
Triplet to triplet absorption in organic molecules for use in photochromic devices by John L Kropp( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

The photochromic properties of several substituted aromatics and heterocyclics have been investigated. The absorption spectra, phosphorescence lifetime T-T absorption spectra and the product of triplet extinction coefficient and triplet formation efficiency, were evaluated for representative compounds. Using these data the photochromic properties of heterocyclics are compared to their hydrocarbon analogs. The values of the maximum triplet formation efficiency are lower for heterocyclics than for aromatics. However, broader T-T absorption and more efficient absorption for pumping light suggest that, on balance, heterocyclics are comparable to aromatic hydrocarbons in their effectiveness as photochromic materials. The variation of solvent induces large changes in the photochromic properties of heterocyclics thus providing a useful additional parameter for adjusting their properties. These differences also promise to shed light on the mechanism of radiationless transitions in these compounds. Recommendations for further studies to improve the photochromic properties of heterocyclics are made
Triplet to triplet absorption in organic molecules for use in photochromic devices by John L Kropp( Book )

1 edition published in 1969 in English and held by 1 WorldCat member library worldwide

This report describes a continuing program of research whose aim is to investigate and evaluate new classes of triplet state photochromic materials. This work is centered upon studies of substituted aromatics and heterocyclic compounds. The effect of solvent composition upon fluorescence, phosphorescence ant T-t absorption has been investigated for several compounds with the aim of determining the conditions for which the photochromic behavior of a compound will be maximized. Studies have been made for benquinolines, dibenzacridines, 6 amino chrysene VII and dibenzo-[c, g]carbazole VIII. Results of these studies are presented and discussed in terms of the solvent influence upon the lone pair of electrons on the nitrogen in aza-aromatics and for VII and VIII in terms of a change in excited state properties compared to the ground state. The photochromic properties of several new compounds, including phenanthrolines and some oxygen containing heterocyclics ; have been investigated. Results reveal one compound, 2,3 dimethyl; 1,4 phenanthroline, shows good promise as a photochromic. Some uses of triplet state photochromics are discussed and conclusions of this work and recommendations for future studies are given
 
Audience Level
0
Audience Level
1
  Kids General Special  
Audience level: 0.95 (from 0.84 for Triplet to ... to 0.99 for Fluorescen ...)

Languages