Measurement of Dipole Moments and Lifetimes of Triplet States of Fluorenone and Its Derivatives by Time Resolved Microwave Dielectric Absorption.
15 Apr 1998-Journal of the Physical Society of Japan (THE PHYSICAL SOCIETY OF JAPAN)-Vol. 67, Iss: 4, pp 1220-1225
TL;DR: In this paper, the authors used microwave dielectric absorption to study the excited triplet states formed by the laser flash photolysis and reported the triplet state lifetime and dipole moments of fluorenone and its derivatives.
Abstract: The technique of time resolved microwave dielectric absorption has been used to study the excited triplet states formed by the laser flash photolysis. The details of the experimental method and apparatus are discussed. The triplet state lifetimes and triplet state dipole moments of fluorenone and its derivatives are reported. The triplet state lifetime of fluorenone agrees with that obtained by optical absorption. The lifetime measurements with argon purging and with air equilibrated solution confirm the formation of triplet states. A marked increase in the triplet state dipole moment of fluorenone and its derivatives is observed and implies that their lowest triplet state is of (π, π * ) in nature.
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TL;DR: In this article, a 2D finite difference time domain (FDTD) was used to evaluate the forward problem and the inverse problem was solved via a Bayesian approach via a posterior distribution over the model parameters such as complex permittivity.
Abstract: : The motivation of this work is to quantify the degradation of aging electrical cables. The dielectric material parameter of insulation can be correlated with degradation. In this paper, the forward problem is posed as a microwave nondestructive evaluation (NDE) problem. A 2D finite difference time domain (FDTD) was used to evaluate the forward problem. The inverse problem is solved via a Bayesian approach. The Bayesian formulation describes the solution as a posterior distribution over the model parameters such as complex permittivity. Since there is no analytical solution for the posterior distribution, the Markov Chain Monte Carlo (MCMC) method is employed to numerically solve for it. The Metropolis-Hasting algorithm is used in particular. Results for computational experiments are demonstrated to show feasibility of this approach.
1 citations
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17 Oct 2011
TL;DR: In this paper, a stochastic inversion technique based on the Metropolis-Hasting algorithm was applied to the problem of quantitative nondestructive evaluation (QNDE) of material aging parameters.
Abstract: : The quantitative nondestructive evaluation (QNDE) of material aging parameters continues to be a very challenging problem. In our approach, we formulated a forward problem arising in specific micro guided wave test. A stochastic inversion technique based on the Metropolis-Hasting algorithm was applied to the problem. The feasibility and validity of the approach was demonstrated through computational experiments.
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References
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TL;DR: In this article, the excited-state dipole moments of aminobenzonitriles have been determined in cyclohexane, benzene, and 1,4-dioxane using time-resolved microwave conductivity (TRMC) and fluorescence spectroscopy techniques.
Abstract: Singlet excited-state dipole moments of a number of aminobenzonitriles have been determined in cyclohexane, benzene, and 1,4-dioxane, using time-resolved microwave conductivity (TRMC) and fluorescence spectroscopy techniques. For the 4-(dialkylamino)benzonitriles (methyl, ethyl, propyl, and decyl) intramolecular charge transfer (ICT) occurs in the excited singlet state even in the nonpolar solvent cyclohexane
339 citations
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01 Dec 1982
TL;DR: In this paper, the application of the time-resolved microwave conductivity (TRMC) technique to the quantitative measurement of charge separation in flash-photolysed molecular systems is desecribed.
Abstract: The application of the time-resolved microwave conductivity (TRMC) technique to the quantitative measurement of charge separation in flash-photolysed molecular systems is desecribed. The apparatus required, background theory and problems involved in deriving absolute values related to the charge-separation process are fully discussed. The use of the technique is illustrated by experiments carried out on the flash photolysis of 4-dimethylamino-4′-nitrostilbene (DMANS) in several solvents. Values of the dipole moments of the T 1 and S 1 states have been estimated and for S 1 are in good agreement with literature values derived in other ways. Other parameters important to the understanding of the photophysics of DMANS are also derived.
225 citations
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TL;DR: In this paper, the flash transient spectrum is given over a wide spectral range in acetonitrile and hydrocarbon solvents, and is assigned to the triplet on the basis of both its decay kinetics and accompanying delayed emission.
Abstract: Flash-photolytic measurements of photophysical parameters of fluorenone are presented. The flash transient spectrum is given over a wide spectral range in acetonitrile and hydrocarbon solvents, and is assigned to the triplet on the basis of both its decay kinetics and accompanying delayed emission. This corresponds spectrally to prompt fluorescence and is accurately second order in transient concentration. Relative triplet quantum yields (phi/sub T/) are obtained from the dependence of the transient absorption on flash energy. Measurements of florescence lifetimes, quantum yields, and phi/sub T/'s give rate constants for all degradative processes of the lowest excited singlet. In acetonitrile the rates of intersystem crossing and internal conversion to the ground state from the lowest excited singlet are comparable. The absence of phosphorescence and the measured triplet lifetime (approximately 2 ms) in rigid media at 77K give a lower limit for the radiative lifetime (tau/sub o/ > 0.2s) which is compatible with a ..pi..-..pi..* assignment for the lowest triplet.
96 citations