Bio: G. Porter is an academic researcher. The author has contributed to research in topics: Absorption spectroscopy & Flash photolysis. The author has an hindex of 1, co-authored 1 publications receiving 43 citations.
TL;DR: The absorption spectrum of triplet benzene has been observed by flash photolysis studies of benzene in rigid hydrocarbon glasses at 77°K as mentioned in this paper, which is the same as the absorption spectrum observed for triplet triplet polycyclic benzene.
Abstract: The absorption spectrum of triplet benzene has been observed by flash photolysis studies of benzene in rigid hydrocarbon glasses at 77°K.
TL;DR: A large number of electrochemical techniques are available for producing and studying cation radicals (or other electrogenerated) and their instrumentation, techniques, and theory are described in this paper.
Abstract: Publisher Summary This chapter discusses chemical oxidations, oxidations on acidic surfaces, and photoionizations. The formation of cation radicals in solution is also discussed. The chapter outlines the experimental techniques that have been used to study cation radicals and the type of information that can be obtained about their behavior. Examples of such investigations are provided. A large number of electrochemical techniques is available for producing and studying cation radicals (or other electrogenerated). Their instrumentation, techniques, and theory are described. The electrochemical techniques can be separated into two classes: the microelectrode or voltammetric techniques and the bulk electrolysis or coulometric techniques. Detailed descriptions of physical properties of cation radicals are presented in the chapter. Cation radicals react with a variety of nucleophiles. Substitution often occurs, but there are many examples in which electron transfer occurs either entirely or in part.
TL;DR: In this article, a double-ζ basis set of contracted Gaussian functions augmented by two diffuse π functions on each carbon atom was used to study the π-electron states of benzene.
Abstract: Ab initio configuration interaction studies of the π-electron states of benzene were carried out with a double-ζ basis set of contracted Gaussian functions augmented by two diffuse π functions on each carbon atom. The core potential of the σ electrons was obtained from an all-electron SCF calculation on the ground state. Vertical excitation energies of 5.00, 7.64, and 8.34 eV were obtained for the 1B2u, 1B1u, and 1E1u states, respectively, corresponding to the e1g→e2u excitation; the first two of these levels have a valencelike electron distribution, but the 1E1u state was found to have a diffuse 1e2u natural orbital, with = 38 bohr2. The analogous set of triplet states, all of which are valencelike, have calculated vertical excitation energies of 3.83 (3B1u), 4.98 (3E1u), and 7.00 eV (3B2u). The low-lying valence states 1E2g (8.33 eV) and 3E2g (7.28 eV) were found to have substantial double-excitation character, but no additional valence E2g states were obtained. Many other states, including quinte...
TL;DR: In this article, it was suggested that the low yields of fluorescence and intersystem crossing in dry solvents are due to dissociation of excited singlet dimer chlorophyll into ground state monomer species.
Abstract: The method of flash photolysis has been used for direct measurement of the quantum yields of triplet formation in dilute chlorophyll solutions at 23 $^\circ$C. In ether solution, the triplet yields were found to be 0.64 and 0.88 for chlorophyll a and b, respectively. In very dry hydrocarbon solution, the yields decrease by at least a factor of 5. It is suggested that the low yields of fluorescence and intersystem crossing in dry solvents are due to dissociation of excited singlet dimer chlorophyll into ground state monomer species.
TL;DR: In this article, the authors determined the quantum yields of triplet state formation and extinction coefficients of the triplet states for solutions of anthracene, phenanthrene, 1,2,5,6-dibenzanthracene and fluorescein.
Abstract: Quantum yields of triplet state formation and extinction coefficients of the triplet states have been determined by direct depletion methods for solutions of anthracene, phenanthrene, 1,2,5,6-dibenzanthracene, fluorescein, dibromofluorescein, eosin and erythrosin. The values obtained for the hydrocarbons are in reasonable agreement with those obtained by other workers using energy transfer and heavy atom perturbation techniques. In all cases which we have studied, the sum of the quantum yields of fluorescence and triplet state formation is equal to unity within the limits of experimental error, showing that radiationless transfer from the excited singlet to the ground state is negligible.
TL;DR: In this paper, a dilute solution of benzene was photolyzed with a KrF excimer laser and the Sn←S1 and Tn←T1 absorption spectra were measured with time-resolved spectroscopy.
Abstract: A dilute solution of benzene was photolyzed with a KrF excimer laser. The Sn←S1 and Tn←T1 absorption spectra are measured with time‐resolved spectroscopy. The Sn←S1 absorptions in the energy range between 850 and 220 nm were analyzed. The transient absorption band at 500 nm, which was observed previously by several workers disappeared completely upon dilution of the sample, and thus was assigned to be the excimer band. We assigned the other states as follows: 620 nm (1E1u, f∼0.003), 540–325 nm (11E2g, f∼0.04), and 270 nm (21E2g, f∼0.12). The observed energies from the ground state to the 11E2g and 21E2g states 7.8 and 9.2 eV, respectively. The Tn←T1 spectrum showed a single peak at 235 nm (f∼0.35) and a shoulder around 310 nm (f∼0.12).