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Photoelectron-imaging spectroscopy, flowing afterglow-photoelectron spectroscopy and the flowing afterglow-selected ion flow tube technique and electronic structure calculations are used for studying the mechanism of the reaction of the hydroxide ion (H[O.sup.-]) with 1H-1,2,3-triazole. Deprotonation of 1H-1,2,3-triazole at the C5 position has initiated fragmentation of the ring structure to yield a minor product, the ketenimine anion.

The reactions of hydrated electron with various radicals are studied in pulse radiolysis experiments. The rate constants of hydrated electron reactions with various reactive radicals are measured over a temperature range of 5-75 degree C, which helps in understanding the hydrated electron radical reaction rates.

The photosensitive Belousov-Zhabotinsky (BZ) reaction was studied on a circular ring that was drawn using computer software and then projected on a film soaked with BZ solution. It was observed that a chemical wave propagated with a constant velocity on the black ring under a bright background under initial conditions and when the background was rapidly changed to dark, coexistence of the oscillation on part of the ring and propagation of the chemical wave on the other part was observed.

The electron affinity (EA), photoelectron spectrum and the spectral analysis of 1-pyrazolide are presented. The thermodynamic properties of the pyrazole system, as well as the electronic structure of the corresponding radicals are discussed.

The photoelectron spectra of AuO(super -) and an isovalent system, AuS(super -) are reported. The results are discussed in relation to the other coinage metal oxides, CuO and AgO and a comparison between gold and other coinage metal oxides reveals the strong relativistic effects in the gold system.

The photosensitive Belousov-Zhabotinsky (BZ) reaction with Ru(bpy)(sub 3)(super 2+) catalyst is used to examine wave propagation and annihilation at the boundaries of excitable and inhibitory regions of an active medium. A boundary layer is formed because of molecular diffusion, where the concentrations of the species are different from those far from the boundary.

Research into spacer dependence of intersystem crossing rates of the free base porphyrin moiety in gable-type copper(II)-free base porphyrin heterodimers involving a new dimer with a phenanthrene bridge is presented. The through-bond interaction is likely to be dominant in controlling the intersystem crossing rate.

In an attempt to expand the utility of the model Hamiltonian technique developed by Köppel, Domcke, and Cederbaum (KDC) [Adv. Chem. Phys. 57, 59 (1984)], an ansatz for quasidiabatic wave functions is introduced in the framework of equation-of-motion coupled-cluster (EOM-CC) theory. Based on the ansatz, the theory for the analytic first derivative of the off-diagonal element of the quasidiabatic potential matrix is developed by extending the theory for the analytic gradient of the EOM-CC energy. This analytic derivative is implemented for EOM-CCSD (singles and doubles approximation) calculations of radicals subject to pseudo-Jahn–Teller and Jahn–Teller interactions. Its applicability in construction of the KDC quasidiabatic model potential is discussed. [ABSTRACT FROM AUTHOR]

The 351.1 nm photoelectron spectrum of the cyclopentadienide ion has been measured, which reveals the vibronic structure of the X 2E1″ state of the cyclopentadienyl radical. Equation-of-motion ionization potential coupled-cluster (EOMIP-CCSD) calculations have been performed to construct a diabatic model potential of the X 2E1″ state, which takes into account linear Jahn–Teller effects along the e2′ normal coordinates as well as bilinear Jahn–Teller effects along the e2′ and ring-breathing a1′ coordinates. A simulation based on this ab initio model potential reproduces the spectrum very well, identifying the vibronic levels with linear Jahn–Teller angular momentum quantum numbers of ±1/2. The angular distributions of the photoelectrons for these vibronic levels are highly anisotropic with the photon energies used in the measurements. A few additional weak photoelectron peaks are observed when photoelectrons ejected parallel to the laser polarization are examined. These peaks correspond to the vibronic levels for out-of-plane modes in the ground X 2E1″ state, which arise due to several pseudo-Jahn–Teller interactions with excited states of the radical and quadratic Jahn–Teller interaction in the X 2E1″ state. A variant of the first derivative of the energy for the EOMIP-CCSD method has been utilized to evaluate the strength of these nonadiabatic couplings, which have subsequently been employed to construct the model potential of the X 2E1″ state with respect to the out-of-plane normal coordinates. Simulations based on the model potential successfully reproduce the weak features that become conspicuous in the 0° spectrum. The present study of the photoelectron spectrum complements a previous dispersed fluorescence spectroscopic study by Miller and co-workers [J. Chem. Phys. 114, 4855 (2001); 114, 4869 (2001)] to provide a detailed account of the vibronic structure of X 2E1″ cyclopentadienyl. The electron affinity of the cyclopentadienyl radical is determined to be 1.808±0.006 eV. This electron affinity and the gas-phase acidity of cyclopentadiene have been combined in a negative ion thermochemical cycle to determine the C–H bond dissociation energy of cyclopentadiene; D0(C5H6,C–H)=81.5±1.3 kcal mol-1. The standard enthalpy of formation of the cyclopentadienyl radical has been determined to be ΔfH298(C5H5)=63.2±1.4 kcal mol-1. [ABSTRACT FROM AUTHOR]

The 351.1 nm photoelectron spectrum of the 1-pyrazolide-d3 anion has been measured. The photoelectron angular distributions indicate the presence of nearly degenerate electronic states of the 1-pyrazolyl-d3 radical. Equation-of-motion ionization potential coupled-cluster singles and doubles (EOMIP-CCSD) calculations have been performed to study the low-lying electronic states. The calculations strongly suggest that three electronic states, energetically close to each other, are accessed in the photodetachment process. Strong interactions of the pseudo-Jahn-Teller type in each pair of the three states are evident in the calculations for the radical at the anion geometry. Model diabatic potentials of the three states have been constructed around the anion geometry in terms of the anion reduced normal coordinates up to the second order. An analytic method to parametrize the quadratic vibronic coupling (QVC) model potentials has been introduced. Parameters of the QVC model potentials have been determined from the EOMIP-CCSD and CCSD(T) calculations. Simulations of the 1-pyrazolide-d3 spectrum have been performed with the model Hamiltonian, treating all vibronic interactions amongst the three states simultaneously. The simulation reproduces the fine structure of the observed spectrum very well, revealing complicated nonadiabatic effects in the low-lying states of the radical. The ground state of the 1-pyrazolyl-d3 radical is 2A2 and the electron affinity is 2.935±0.006 eV. The first excited state is 2B1 with a term energy of 32±1 meV. While the high-symmetry (C2v) stationary points of the X 2A2 and à 2B1 states are minima, that of the state is a saddle point as a result of the pseudo-Jahn-Teller interactions with the other two states. The topology of the adiabatic potential energy surfaces is discussed. [ABSTRACT FROM AUTHOR]

Recently, it has been proposed that various kinds of time operations can be performed using an excitable field, mainly based on computer simulation. In this study, we performed experiments toward the realization of a time operation, such as time-difference detection. We used the photosensitive Belousov–Zhabotinsky reaction as a spatially distributed excitable field. We found that a single geometrical circuit can perform different operations with changes in the intensity of light illumination. The experimental results are discussed in relation to the idea of a non-Neumann-type computational device. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The 351.1 nm photoelectron spectra of the N-methyl-5-pyrazolide anion and the N-methyl-5-imidazolide anion are reported. The excellent agreement is found with the calculated FC factors for the N-methyl-5-pyrazolyl radical.

The 351.1nm photoelectron spectrum of imidazolide anion is measured. The thermodynamic parameters for imidazole and imidazolyl radical are compared with those for pyrrole and pyrrolyl radical and the effects of the additional N atom in the five-membered ring are discussed.

An excitable field in the shape of a circular ring or figure '8' that was drawn by the computer software and then projected on a film soaked with Belousov-Zhabotinsky (BZ) solution using a liquid-crystal projector is used to investigate the propagation of chemical waves in the photosensitive BZ reaction. The results suggest that the photosensitive BZ reaction is useful for creating spatio-temporal patterns depending on the geometric arrangement of excitable fields.

The photoelectron spectrum of pyrrolide was measured and the EA of pyrrolyl was determined to be 2.145 plus minus 0.010 eV. The EA value and the N-H BDE of pyrrole were combined in a thermochemical cycle to determine the gas-phase acidy of pyrrole.

Inverted (A/E) chemically induced dynamic electron polarization (CIDEP) is observed for random encounters of radical pairs such as the phenoxyl radical together with either e(sub aq)(super -) or the radical anion of benzoate. Inverted polarization (A/E) was found for e(sub aq)(super -) or the radical anions of benzoateand 4-methyl, 4-methoxy, and 4-carboxybenzoates in the presence of phenoxyl or 4-methylphenoxyl radicals.