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Fractionalization is a phenomenon in which strong interactions in a quantum system drive the emergence of excitations with quantum numbers that are absent in the building blocks. Outstanding examples are excitations with charge e/3 in the fractional quantum Hall effect.sup.1,2, solitons in one-dimensional conducting polymers.sup.3,4 and Majorana states in topological superconductors.sup.5. Fractionalization is also predicted to manifest itself in low-dimensional quantum magnets, such as one-dimensional antiferromagnetic S = 1 chains. The fundamental features of this system are gapped excitations in the bulk.sup.6 and, remarkably, S = 1/2 edge states at the chain termini.sup.7-9, leading to a four-fold degenerate ground state that reflects the underlying symmetry-protected topological order.sup.10,11. Here, we use on-surface synthesis.sup.12 to fabricate one-dimensional spin chains that contain the S = 1 polycyclic aromatic hydrocarbon triangulene as the building block. Using scanning tunnelling microscopy and spectroscopy at 4.5 K, we probe length-dependent magnetic excitations at the atomic scale in both open-ended and cyclic spin chains, and directly observe gapped spin excitations and fractional edge states therein. Exact diagonalization calculations provide conclusive evidence that the spin chains are described by the S = 1 bilinear-biquadratic Hamiltonian in the Haldane symmetry-protected topological phase. Our results open a bottom-up approach to study strongly correlated phases in purely organic materials, with the potential for the realization of measurement-based quantum computation.sup.13. Using scanning tunnelling microscopy and spectroscopy, fractional edge excitations are observed in nanographene spin chains, enabling the potential to study strongly correlated phases in purely organic materials., Author(s): Shantanu Mishra [sup.1] [sup.9] , Gonçalo Catarina [sup.2] [sup.3] , Fupeng Wu [sup.4] , Ricardo Ortiz [sup.3] , David Jacob [sup.5] [sup.6] , Kristjan Eimre [sup.1] , Ji Ma [...]

In this work, the excited state dynamical behavior of a novel [pi]-conjugated dye 2,2'-((5-(2-(4-methoxyphenyl)ethenyl)-benzene-1,1-diyl)-bis-(nitrilomethylylidene)-diphenol) (C1) has been investigated. Two intramolecular hydrogen bonds of C1 are tested to pre-existing in the ground state via AIM and reduced density gradient. Using a time-dependent density functional theory (TDDFT) method, it has been substantiated that the intramolecular hydrogen bonds of C1 should be strengthened in the S1 state via analyzing fundamental bond length, bond angles, and corresponding infrared vibrational modes. The most obvious variation of these two hydrogen bonds is the O4-H5***N6 bond, which might play important roles in excited state behavior for the C1 system. Furthermore, based on electronic excitation, charge transfer could occur. Just due to this kind of charge re-distribution, two hydrogen bonds should be tighter in the first excited state, which is consistent with the variation of hydrogen bond lengths. Thus, the phenomenon of charge transfer is reasonable evidence for confirming the occurrence of the excited state proton transfer (ESPT) process in the [S.sub.1] state. Our theoretically constructed potential energy surfaces of C1 show that excited state single proton transfer should occur along with the O4-H5***N6 hydrogen bond rather than the O1-H2***N3 bond. We not only clarify the ESIPT mechanism for C1 but put forward new affiliation and explain a previous experiment successfully. Key words: ESIPT, AIM, MOs, potential energy surfaces. Resume : Dans le cadre des presents travaux, nous avons soumis un nouveau colorant a conjugaison[pi], le2,2' ((5-(2-(4-methoxyphenyl) ethenyl)benzene-1,1-diyl)-bis-(nitrilomethylylidene)diphenol) (C1), a une etude theorique en vue d'examiner son comportement dynamique a l'etat excite. Nous avons analyse deux liaisons hydrogene intramoleculaires du C1 par rapport a la forme preexistante a l'etat fondamental au moyen de la theorie quantique des atomes dans les molecules (AIM) et du gradient de densite reduite. A l'aide de la methode de la theorie de la fonctionnelle de la densite dependante du temps (TD DFT), nous avons etabli, par analyse de la longueur fondamentale des liaisons, des angles de liaison et des modes vibrationnels correspondants en infrarouge, que les liaisons hydrogene intramoleculaires du C1 seraient renforcees dans l'etat [S.sub.1]. La forme la plus evidente de ces deux liaisons hydrogene est la forme O4 H5***N6, qui pourrait jouer un role important dans le comportement a l'etat excite du systeme C1. De plus, selon l'excitation electronique, un transfert de charge pourrait avoir lieu. En raison seulement de ce type de redistribution de charge, les deux liaisons hydrogene devraient etre plus rigides dans le premier etat excite, ce qui concorde avec les variations de longueur des liaisons hydrogene. Par consequent, le phenomene de transfert de charge est une preuve acceptable que le transfert de proton a l'etat excite (TPEE) se produit dans l'etat [S.sub.1]. Les surfaces d'energie potentielle theoriques que nous avons generees pour le C1 montrent que le transfert d'un proton unique a l'etat excite se produirait a la liaison hydrogene O4 H5***N6 plutot qu'a la liaison hydrogene O1 H2***N3. Non seulement nous clarifions le mecanisme de TPIEE du C1, mais nous proposons une nouvelle avenue qui permet d'expliquer les resultats experimentaux obtenus precedemment. [Traduit par la Redaction] Mots-cles : TPIEE, AIM, OM, surfaces d'energie potentielle., Introduction As a topic of much attention in recent years, excited state intra- or inter-molecular proton transfer (ESIPT) reaction exists in various aspects due to its relevance in photo-physical and [...]

Quantum phase transitions (QPTs) involve transformations between different states of matter that are driven by quantum fluctuations.sup.1. These fluctuations play a dominant part in the quantum critical region surrounding the transition point, where the dynamics is governed by the universal properties associated with the QPT. Although time-dependent phenomena associated with classical, thermally driven phase transitions have been extensively studied in systems ranging from the early Universe to Bose-Einstein condensates.sup.2-5, understanding critical real-time dynamics in isolated, non-equilibrium quantum systems remains a challenge.sup.6. Here we use a Rydberg atom quantum simulator with programmable interactions to study the quantum critical dynamics associated with several distinct QPTs. By studying the growth of spatial correlations when crossing the QPT, we experimentally verify the quantum Kibble-Zurek mechanism (QKZM).sup.7-9 for an Ising-type QPT, explore scaling universality and observe corrections beyond QKZM predictions. This approach is subsequently used to measure the critical exponents associated with chiral clock models.sup.10,11, providing new insights into exotic systems that were not previously understood and opening the door to precision studies of critical phenomena, simulations of lattice gauge theories.sup.12,13 and applications to quantum optimization.sup.14,15. A Rydberg atom quantum simulator with programmable interactions is used to experimentally verify the quantum Kibble-Zurek mechanism through the growth of spatial correlations during quantum phase transitions., Author(s): Alexander Keesling [sup.1] , Ahmed Omran [sup.1] , Harry Levine [sup.1] , Hannes Bernien [sup.1] , Hannes Pichler [sup.1] [sup.2] , Soonwon Choi [sup.1] , Rhine Samajdar [sup.1] , [...]

Quantum entanglement for two electrons in the excited states of helium-like atom or ions is investigated using two-electron wave functions constructed in the B-spline basis. As a measure of spatial (electron--electron orbital) entanglement, the von Neumann entropy and linear entropy of the reduced density matrix are calculated for the 1s2s [sup.1,3]S excited states for systems with some selected Z values from Z = 2 to 100. Results for the helium atom are compared with other available calculations. We have also investigated the entropies for these excited states when the nucleus charge is reduced from Z = 2 continuously to Z = 1. At such a critical charge, all the singly excited states of this system become unbound, and the linear entropies and the von Neumann entropies for the excited states approach 1/2 and 1, respectively; the limits for the entropies when one electron is bound to the nucleus, and the other is free. PACS Nos.: 31.15.vj, 31.15.ve, 03.67.Mn. Nous etudions l'intrication quantique de deux electrons dans des etats excites d'atomes et d'ions de type helium en utilisant une fonction d'onde construite sur une base de B splines. Afin de mesurer l'intrication spatiale (orbitale electron electron), nous calculons l'entropie de von Newmann et l'entropie lineaire de la matrice de densite reduite pour les etats excites 1s2s [sup.1,3]S pour des systemes de valeur de Z allant de 2 a 100. Les resultats pour l'helium sont compares aux autres valeurs calculees disponibles. Nous analysons egalement les entropies pour ces etats excites lorsque la charge du noyau est reduite continuellement de Z = 2 a 1. A une telle charge critique, tous les etats simplement excites de ce systeme deviennent non lies et les entropies lineaire et de von Newmann pour les etats excites tendent vers les valeurs 1/2 et 1 respectivement, les valeurs limites lorsqu'un electron est lie au noyau et l'autre est libre. [Traduit par le Redaction], 1. Introduction There has been considerable interest in the investigation of quantum entanglement for biparticle atomic systems. Understanding of entangled systems is important in other research areas, such as quantum [...]

Crucial to many light-driven processes in transition metal complexes is the absorption and dissipation of energy by 3d electrons (1-4). But a detailed understanding of such non-equilibrium excited-state dynamics and [...]

Time-dependent auxiliary density perturbation theory (TDADPT) is extended to the calculation of excited states. The resulting time-dependent auxiliary density functional theory (TDADFT) is structurally identical to the original formulation of Casida. However, significant simplifications occur for the Coulomb and exchange-correlation response due to the underlying auxiliary density functional theory. Here, we present the working equations for TDADFT and a new implementation. Because this new parallel TDADFT implementation is particularly well suited for the calculation of large numbers of excitations, we validate it by the calculation of photoabsorption spectra. Direct comparison with experiment underlines the accuracy and reliability of TDADFT. For selected peaks of the studied polycyclic aromatic hydrocarbon spectra, the assignments of the underlying excitations are also presented. Key words: photoabsorption spectra, polycyclic aromatic hydrocarbons, time-dependent auxiliary density functional theory, perturbation theory. On etend la theorie de la perturbation de la fonctionnelle de la densite auxiliaire dependantes du temps (TDADPT) au calcul des etats excites. La theorie de la fonctionnelle de la densite auxiliaire dependante du temps (TDADFT) resultante est structurellement identique a la formulation originale de Casida. Cependant, la theorie de la fonctionnelle de la densite auxiliaire sous-jacente donne lieu a des simplifications importantes de la reponse coulombienne et d'echange-correlation. On presente ici les equations de travail pour la TDADFT ainsi qu'une nouvelle mise en ceuvre. Comme cette nouvelle mise en ceuvre parallele de la TDADFT convient particulierement bien pour le calcul de grands nombres d'excitations, on la valide par le calcul des spectres de photoabsorption. Une comparaison directe avec l'experience met en relief l'exactitude et la fiabilite de la TDADFT. On presente aussi l'attribution des excitations sous-jacentes pour certains pics des spectres des hydrocarbures aromatiques polycycliques etudies. [Traduit par la Redaction] Mots-cles: spectres de photoabsorption, hydrocarbures aromatiques polycycliques, theorie de la fonctionnelle de la densite auxiliaire dependante du temps, theorie des perturbations., Introduction Time-dependent density functional theory (TDDFT) is the generalization of ground state density functional theory (DFT) to time-dependent phenomena. (1-12) In most practical applications, TDDFT is employed to describe the [...]

Rydberg atoms have an electron in a state with a very high principal quantum number, and as a result can exhibit unusually long-range interactions. One example is the bonding of two such atoms by multipole forces to form Rydberg-Rydberg molecules with very large internuclear distances (1-3). Notably, bonding interactions can also arise from the low-energy scattering of a Rydberg electron with negative scattering length from a ground-state atom (4,5). In this case, the scattering-induced attractive interaction binds the ground-state atom to the Rydberg atom at a well-localized position within the Rydberg electron wavefunction and thereby yields giant molecules that can have internuclear separations of several thousand Bohr radii (6-8). Here we report the spectroscopic characterization of such exotic molecular states formed by rubidium Rydberg atoms that are in the spherically symmetric s state and have principal quantum numbers, n, between 34 and 40. We find that the spectra of the vibrational ground state and of the first excited state of the Rydberg molecule, the rubidium dimer Rb(5s)-Rb(ns), agree well with simple model predictions. The data allow us to extract the s-wave scattering length for scattering between the Rydberg electron and the ground-state atom, Rb(5s), in the low-energy regime (kinetic energy, < 100 meV), and to determine the lifetimes and the polarizabilities of the Rydberg molecules. Given our successful characterization of s-wave bound Rydberg states, we anticipate that p-wave bound states (9), trimer states (10) and bound states involving a Rydberg electron with large angular momentum--so-called trilobite molecules (5)--will also be realized and directly probed in the near future., In 1934, Fermi introduced the ideas of scattering length and pseudopotential to describe the scattering of a low-energy electron from a neutral atom (4). Although the polarization potential for electron-atom [...]

The positive and negative parity states of the even-even [sup.98-108]Ru isotopes are studied within the frame work of the interacting boson approximation model (IBA-1). The calculated levels energy, potential energy [...]

We report a comprehensive study of the quantum-state correlation property of product pairs from reactions of chlorine atoms with both the ground-state and the CH stretch-excited CH[D.sub.3]. In light of available ab initio theoretical results, this set of experimental data provides a conceptual framework to visualize the energy-flow pattern along the reaction path, to classify the activity of different vibrational modes in a reactive encounter, to gain deeper insight into the concept of vibrational adiabaticity, and to elucidate the intermode coupling in the transition-state region. This exploratory approach not only opens up an avenue to understand polyatomic reaction dynamics, even for motions at the molecular level in the fleeting transition-state region, but it also leads to a generalization of Polanyi's rules to reactions involving a polyatomic molecule. mode-specific chemistry | Polanyi's rules | product pair correlation

Molecular function is often predicated on excursions between ground states and higher energy conformers that can play important roles in ligand binding, molecular recognition, enzyme catalysis, and protein folding. The tools of structural biology enable a detailed characterization of ground state structure and dynamics; however, studies of excited state conformations are more difficult because they are of low population and may exist only transiently. Here we describe an approach based on relaxation dispersion NMR spectroscopy in which structures of invisible, excited states are obtained from chemical shifts and residual anisotropic magnetic interactions. To establish the utility of the approach, we studied an exchanging protein (Abp1p SH3 domain)-ligand (Ark1p peptide) system, in which the peptide is added in only small amounts so that the ligand-bound form is invisible. From a collection of [sup.15]N, [sup.1]HN, [sup.13][C.sup.[alpha]] and [sup.13]CO chemical shifts, along with [sup.1]HN- [sup.15]N, [sup.1][H.sup.[alpha]]-[sup.13][C.sup.[alpha]], and [sup.1]HN-[sup.13]CO residual dipolar couplings and [sup.13]CO residual chemical shift anisotropies, all pertaining to the invisible, bound conformer, the structure of the bound state is determined. The structure so obtained is cross-validated by comparison with [sup.1]HN-[sup.15]N residual dipolar couplings recorded in a second alignment medium. The methodology described opens up the possibility for detailed structural studies of invisible protein conformers at a level of detail that has heretofore been restricted to applications involving visible ground states of proteins. Carr-Purcell-Meiboom-Gill (CPMG) | dynamics | excited state structure | residual dipolar couplings | chemical exchange

Excited electronic states created by UV excitation of the diribonucleoside monophosphates ApA, ApG, ApC, ApU, and CpG were studied by the femtosecond transient-absorption technique. Bleach recovery signals recorded at 252 nm show that long-lived excited states are formed in all five dinucleosides. The lifetimes of these states exceed those measured in equimolar mixtures of the constituent mononucleotides by one to two orders of magnitude, indicating that electronic coupling between proximal nucleobases dramatically slows the relaxation of excess electronic energy. The decay rates of the long-lived states decrease with increasing energy of the charge-transfer state produced by transferring an electron from one base to another. The charge-transfer character of the long-lived states revealed by this analysis supports their assignment to excimer or exciplex states. Identical bleach recovery signals were seen for ApA, [(A).sub.4], and poly(A) at delay times >10 ps after photoexcitation. This indicates that excited states localized on a stack of just two bases are the common trap states independent of the number of stacked nucleotides. The fraction of initial excitations that decay to long-lived exciplex states is approximately equal to the fraction of stacked bases determined by NMR measurements. This supports a model in which excitations associated with two stacked bases decay to exciplex states, whereas excitations in unstacked bases decay via ultrafast internal conversion. These results establish the importance of charge transferquenching pathways for UV-irradiated RNA and DNA in roomtemperature solution. DNA excited states | DNA photodamage | electronic structure | femtosecond spectroscopy

High-pressure methods are increasingly used to produce new dense materials with unusual properties. Increasing efforts to understand the reaction mechanisms at the microscopic level, to set up and optimize synthetic approaches, are currently directed at carbon-based solids. A fundamental, but still unsolved, question concerns how the electronic excited states are involved in the high-pressure reactivity of molecular systems. Technical difficulties in such experiments include small sample dimensions and possible damage to the sample as a result of the absorption of intense laser fields. These experimental challenges make the direct characterization of the electronic properties as a function of pressure by linear and nonlinear optical spectroscopies up to several GPa a hard task. We report here the measurement of two-photon excitation spectra in a molecular crystal under pressure, up to 12 GPa in benzene, the archetypal aromatic system. Comparison between the pressure shift of the exciton line and the monomer fluorescence provides evidence for different compressibilities of the ground and first excited states. The formation of structural excimers occurs with increasing pressure involving molecules on equivalent crystal sites that are favorably arranged in a parallel configuration. These species represent the nucleation sites for the transformation of benzene into amorphous hydrogenated carbon. The present results provide a unified picture of the chemical reactivity of benzene at high pressure. benzene crystal | electronic transitions | high-pressure chemistry | two-photon spectroscopy

Excited-state behavior of eight [alpha]-alkyl dibenzyl ketones that are capable of undergoing type II and/or type I photoreactions is studied in isotropic solution and within a water-soluble capsule. The variation in the photochemistry of the guest within the capsule, with respect to the [alpha]-alkyl chain length of the guest, has highlighted the importance of how a small variation in supramolecular structure can affect the selectivity within a confined nanoscale reactor.

New labeling approach and NMR experiments are described along with those that has probed the exchange by using [super 15]N and [super 1]H N nuclei. The experimental data has showed that for many systems accurate excited-state chemical shifts can be measured, thus opening a possibility of obtaining quantitative structural information of invisible states of the sort that is recorded on ground states of proteins.

A number of experiments on different molecular systems are performed to investigate the influence of electronic transitions on the optimization process. It is observed that the modulation of the spectral amplitudes has the little influence on the mode ratios.

A detailed investigation of the dynamics of the reactions of ground and excited state carbon atoms, C[sup.3.P] and C[sup.1.D] is reported. The astrophysical implications of the study are discussed.

Laser flash photolysis and theoretical spin density analysis are used to study the radical and excited-state dynamics of puerarin. The photoexcitation of neutral puerarin in acetonitrile produces a long-lived triplet excited-state, while its phenoxyl radicals, which are insensitive to oxygen and the photoexcitation of anionic puerarin, result in formation of just the radical species.

The formation of OH product in the direct overtone photodissociation of [CH.sub.3][CH.sub.2]OOH at [5V.sub.OH] is discussed. Vibrational-torsional model is used for the simulation of the spectra in the [5V.sub.OH] region for the trans and gauche conformers.

The pump-probe photoionization of isolated benzonitrile (BN) and phenylacetylene (PA) in a supersonic beam is discussed. Results suggest the production of a low-ionization-potential species, which lasts more than hundreds of microseconds after excitation to the [S.sub.1] states.

The application of the ion mobility technique for separating the electronic states of first-, second-, and third-row transition metal cations generated by the laser vaporization/ionization (LVI) technique is presented. Results suggest the presence of two or three mobility peaks corresponding to ground and excited states of different electronic configurations.

Intramolecular hydrogen-atom transfer dependence conjugation of curcumin and related molecular models in the ground state and excited state are analyzed at the first-principles electronic structure level. It is revealed that the larger, more conjugated, systems exhibit a lower reaction barrier in the ground state but a higher barrier in the excited state.

Collision depopulation cross sections of 13 single, highly vibrationally excited levels with 45000 [cm.sup.-1] energy in the electronic ground state of S[O.sub.2] are measured. The relaxation cross sections of these highly excited states, range from 27 to 187 [Angstrom.sub.2] with an average of 71 [Angstrom.sub.2].

The impact of the excited-state absorption (ESA) and two-exciton processes on the development of an adiabatic rapid passage (ARP) in a three-state system with non-Markovian relaxation is explained. ESA is shown to highly affect the coherent population transfer in large molecules.

The electronic structure of the ground and low-lying states of the CeF molecule is studied by using Dirac-Fock-Roothaan (DFR) and four-component relativistic single and double excitation configuration interaction (SDCI) calculations in the reduced frozen-core approximation (RFCA). The results have shown that the bonding in the ground and excited states of the CeF molecule is affected by the 6s and 5d electron distributions between the Ce and the F.

The absorption, emission and excitation spectra of the solutions of 1-azacarbazole (1AZC) dimers in a low-viscosity solvent, such as 2-methylbutane (2MB) are examined. The results have revealed that 1AZC at a [10.sup.-4] M solution in 2MB does not display doubly hydrogen bonded centrosymmetric dimer emission as the temperature decreases from room temperature up to 113 K.

The density functional theory (DFT) calculations are used for studying the potential-energy surface of the first excited state of the 11-cis-retinal protonated Schiff base (PSB11) chromophore. The studies have suggested few reaction pathways on the potential-energy surface of the excited state leading toward the conical interaction and resulting in a cis to trans isomerization of the retinal chromophore.

Charge-transfer quenching of the singlet excited states of cyanoaromatic electron acceptors by pyridine is characterized by using a driving force dependence reactions. Evidence is provided for bonded exciplex intermediate from studies of steric and Coulombic effects on the quenching rate constants, which have shown a curve crossing between the ground state and the low-energy bonded exciplex state.

Two complementary series of [C.sub.60]-[(Fl).sub.n] and [C.sub.60]-[(Fl).sub.n]-[C.sub.60] (Fl = 9,9-dihexylfluorene-2,7-diyl, n = 1-5) derivatives with terminal N-methylfulleropyrrolidine units are synthesized from CHO-[(Fl).sub.n] and CHO-[(Fl).sub.n]-CHO precursors via 1,3-dipolar cycloaddition reaction. It is shown that an efficient transduction of singlet excited-state energy transfer has prevailed from the photoexcited oligofluorene to the energy accepting fullerene.

The fluorescence of the DNA double helix [(dA).sub.20].[(dT).sub.20] was studied by fematosecond spectroscopy. It was found that the fluorescence decays are slower than those of the monomeric chromophores dAMP and TMP and the fluorescence anisotropy decays show strong wavelength dependence.

A systematic fluorescence and laser-flash photolysis study on several model dyads that contain the chromophores of flurbiprofen (FBP) and tryptophan (Trp) which are the relevant amino acids present in site I of human serum albumin is presented.

The photodetachment efficiency in the gas phase was monitored to measure the electronic absorption spectra of bare and methanol-solvated radical anions of benzophenone and acetophenone. Strong absorption bands were observed due to autodetachment after transitions to bound excited states, in benzophenone, the solvation of two methanol molecules exhibit the near convergence to the limit and acetophenone molecules have relatively small shifts.

The [V.sup.}([H.sub.2]O) and Ar[V.sup.}([H.sub.2]O) complexes were studied by coupled-cluster methods including single and double excitations (CCSD). The ground state was predicted to be [5.sup.A.sub.1] for [V.sup.}([H.sub.2]O) but argon tagging was found to change the lowest lying state to [5.sup.B.sub.1] for [V.sup.}([H.sub.2]O) and zero-point vibration averaging increases the effective bond angle.

The helium droplet isolation (HENDI) method combined with fematosecond pump-probe spectroscopy were sued to investigate the dynamics of vibrational wave packets excited in [Na.sub.2] dimers in triplet states. The results show that the wave packet dynamics appear to be unperturbed by the helium droplet environment.

The excited state dynamics of silver atoms embedded in helium nanodroplets were investigated by various spectroscopic techniques.

The vibrationally mediated photodissociation dynamics of [C.sub.2][H.sub.4.sup.} excited through the [B.sup.2][A.sub.g] state are described. Analysis of the multimass images yielded both the translational energy distributions for the two dissociation channels and the branching between them as a function of excitation energy and the dissociation of ions consistently gave enhanced branching to the H elimination channel.

The fully analyzed high-resolution spectrum of the carboxylic acid dimer [(HCOOH).sub.2] in the gas phase is described. The antisymmetric C-O stretch vibration were recorded by high resolution IR spectra and the proton transfer time of 1.0 and 1.7 ns for the ground and the vibrationally excited state, respectively was determined.

Experimental and theoretical methods are used for characterizing a series of Ir(III)-based heteroleptic complexes with phenylpyridine (ppy) and 2-(5-phenyl-4H-[1,2,4]-triazol-3-yl)pyridine (ptpy) derivatives as coordinating ligands. The results have shown that the extent of charge-transfer contributions have depended on the energy gaps between the relevant molecular orbitals, which can be modified by the substitution pattern.

The photoacid pyranine is used as a molecular probe for analyzing the properties of confined water and diffusive proton-transfer kinetics in the nanoscopic water channels of Nafion fuel cell membranes at various hydration levels, which are compared to water in a series of well-characterized Aerosol OT (AOT) reverse micelles with known water nanopool sizes. The effective size of the Nafion water channels at various hydration levels are obtained by a known size of the AOT reverse micelles that exhibit the corresponding proton-transfer kinetics and orientational relaxation.

The synthesis and characterization of a series of water-soluble 2-(2'-arylsulfonamidophenyl)benzimidazole derivatives containing electron-donating and accepting groups attached to various positions of the fluorophore [pi]-system in aqueous solution are described. The analysis has described the substituent effects on the photophysical properties of this class of excited-state intramolecular proton transfer (ESIPT) fluorophores in an aqueous environment and has also given guidelines for designing emission ratiometric pH.

The photochemistry of N-nitrosodimethylamine after excitation to the [S.sub.1] and [S.sub.2] states is analyzed with the complete active space self-consistent field method (CASSCF) and the second-order multiconfigurational perturbation theory (CASPT2). The relative energy of the respective transition states have indicated that these paths are forbidden and do not compete with homolytic dissociation.

The functionalization of gold nanorods with a thiol derivative of ruthenium (II) tribipyridyl complex in dodecanethiol is described. The results suggest that the size and shape of the gold nanorods impact the quenching of the excited state to proceed via an energy transfer mechanism and those gold rods are capable to deactivate excited ruthenium.

The rate constants for radiative decay, radiationless decay, and intersystem crossing for a range of excited states formed by reaction of cyanoanthracene acceptors with alkylbenzenes as donors in different solvents of moderate to low polarity are presented. The basic parameters that govern the rate constants for radiationless decay in excited states with intermediate charge-transfer character are described.

A comparison to determine the factors dominating inverted region electron transfer of the varying trends of back electron transfer (or nonradiative decay) of metal-to-metal charge transfer (MMCT) to metal-to-ligand charge transfer (MLCT) excited states of simple transition metal complexes, is done. The model provides a good base for qualitatively distinguishing various classes of excited-state dynamic behavior.

Modifications of the scaled second-order perturbation corrections to configuration interaction with single substitutions are suggested. There two approaches described and their accuracy is found to be comparable which arises from a strong correlation between the same-spin and the opposite spin portions of the excitation energy terms.

Ab initio electronic structure and dynamical calculations were carried out to explore the photochemical processes following optical excitation of the glycine molecule into its two low-lying excited states. The calculations led to identification of possible dynamical pathways, quenching into the n[pi*]-state minimum and subsequent slow dynamics, N-H bond dissociation and hydrogen transfer.

The resonance Raman spectra of thymine in aqueous solution was measured to explore the excited -state structural dynamics of thymine. The C=C stretching and C-H deformation vibrational modes were found to exhibit maximum Raman intensity and structural change upon photoexcitation by thymine indicating than the initial dynamics of thymine lie along the photochemical reaction coordinate.

The Franck-Condon (FC) factors for the lowest energy molecular nature electronic transition was calculated by employing ground- and excited-state geometries to determine the origin of the intensity of 0 -> 0 and 0 -> 1 vibronic bands.

The large amplitude ac excitation effects on the polarization-electric-field (P-E) and strain-electric-field characteristics of both hard and soft Pb(Zr, Ti)[O.sub.3] ceramics are examined. The results have shown that additional domain release mechanism contributing to enhanced electromechanical response is present besides the decrease of E axis upon ac excitation.