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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05 May 2012
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
Cites background from "Measurement of Dipole Moments and L..."
...Time-Resolved Microwave Dielectric Absorption (TRMDA) enables the measurement of the evanescent electrical field leaking from the probe into the cable insulation by using cavity resonator [2]....
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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.
Cites background from "Measurement of Dipole Moments and L..."
...Time-Resolved Microwave Dielectric Absorption (TRMDA) enables to measure evanescent electrical field leaking from the probe into the cable insulation by using cavity resonator [2]....
[...]
References
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TL;DR: In this paper, the dipole moment of the benzylperoxyl radical in benzene, cyclohexane, and decane solutions was measured using microwave dielectric absorption.
Abstract: The technique of time-resolved microwave dielectric absorption has been used to measure the dipole moment of the benzylperoxyl radical in benzene, cyclohexane, and decane solutions. The radicals were produced by photolysis of dibenzyl ketone in oxygen-containing solutions with pulses of light at 280 nm from a frequency-doubled dye laser. Benzyl chloride and cyanide were used to model the rotational relaxation behavior of the radical. A dipole moment of 2.4 +/- 0.2 D was found. It is suggested that this polarity may be large enough to significantly affect the location of the portion of the molecule bearing the peroxyl group in radicals formed in heterogeneous systems as micelles or bilayers in water. 16 references, 1 figure, 4 tables.
38 citations
TL;DR: In this paper, the dipole moments of the lowest 3 nπ ∗ and 1 nπ∗ excited states of benzophenone have been determined by optical spectroscopic methods and are 1.79 D and 1.46 D respectively.
Abstract: The dipole moments of the lowest 3 nπ ∗ and 1 nπ ∗ excited states of benzophenone have been determined by optical spectroscopic methods and are 1.79 D and 1.46 D respectively; these values refer to the benzophenone molecules in a polar lattice assuming a ground state moment of 2.98 D. It was possible to obtain an accurate comparison of the change in dipole moment for the singlet and triplet states of Δ μ s Δ μ τ = 0.78 , and this number most likely does not depend so critically on the details of the microscopic part of the internal field.
24 citations
TL;DR: In this article, the transient conductivity of CdS has been studied by nanosecond time-resolved microwave conductivity, and the ratio of the electron-hole pair mobility to the pair formation energy is determined to be 42 − plus minus 6 − 6 − 1/eV.
Abstract: The transient conductivity resulting from pulsed irradiation (with 3-MeV electrons) of a single, high-resistivity (4 {times} 10{sup 7} {Omega} m) crystal of CdS has been studied by nanosecond time-resolved microwave conductivity. The ratio of the electron-hole pair mobility to the pair formation energy is determined to be 42 {plus minus} 6 {times} 10{sup {minus}4} m{sup 2} V{sup {minus}1} s{sup {minus}1}/eV. For end-of-pulse pair concentrations less than ca. 10{sup 19} m{sup {minus}3}, the half-life of electrons toward localization was 25 ns. With increasing pair concentration above this value, the lifetime was found to become longer. This effect is attributed to trap saturation with the trap concentration estimated to be 3 {times} 10{sup 19} m{sup {minus}3} (5 {times} 10{sup {minus}8} M) with a rate constant toward trapping of 1.1 {times} 10{sup {minus}12} m{sup 3} s{sup {minus}1} (6.6 {times} 10{sup 14} M{sup {minus}1} s{sup {minus}1}). The main trapping site is thought to be the singly ionized sulfur vacancy. No evidence was found for the occurrence of direct electron-hole recombination, and an upper limit of 3 {times} 10{sup {minus}14} m{sup 3} s{sup {minus}1} (ca. 2 {times} 10{sup 13} M{sup {minus}1} s{sup {minus}1}) could be placed on the second-order rate constant for this process.
24 citations
22 citations
TL;DR: In this paper, the formation and decay of charge transfer (CT) states resulting from photo-induced intramolecular electron transfer from carbazole to tetrachlorophthalimide joined by di-, tri-, tetra-, and hepta-methylene spacers has been studied by the time-resolved microwave conductivity (TRMC) technique in the solvents cyclohexane, trans-decalin, benzene, and para-dioxane.
Abstract: The formation and decay of charge transfer (CT) states resulting from photo-induced intramolecular electron transfer from carbazole to tetrachlorophthalimide joined by di-, tri-, tetra-, and hepta-methylene spacers has been studied by the time-resolved microwave conductivity (TRMC) technique in the solvents cyclohexane, trans-decalin, benzene, and para-dioxane. Both short-lived, singlet, and long-lived, triplet, CT states are observed. The triplet CT state can be formed by intersystem crossing from the singlet CT state subsequent to electron transfer, as is the case for the three shortest bridge compounds, and also via formation of the local acceptor triplet state prior to electron transfer, in the case of the hepta-methylene compound.
22 citations