Showing papers on "Excited state published in 1992"
TL;DR: Because the photoluminescence in the conducting polymer is quenched by interaction with C60, the data imply that charge transfer from the excited state occurs on a picosecond time scale.
Abstract: Evidence for photoinduced electron transfer from the excited state of a conducting polymer onto buckminsterfullerene, C(60), is reported. After photo-excitation of the conjugated polymer with light of energy greater than the pi-pi* gap, an electron transfer to the C(60) molecule is initiated. Photoinduced optical absorption studies demonstrate a different excitation spectrum for the composite as compared to the separate components, consistent with photo-excited charge transfer. A photoinduced electron spin resonance signal exhibits signatures of both the conducting polymer cation and the C(60) anion. Because the photoluminescence in the conducting polymer is quenched by interaction with C(60), the data imply that charge transfer from the excited state occurs on a picosecond time scale. The charge-separated state in composite films is metastable at low temperatures.
4,016 citations
TL;DR: In this article, the activation energy of the A1C02 reaction is 2.5 and 3.9 kcal/mol, respectively, while the experimentally estimated heat of reaction is about 5 kcal/molecular.
Abstract: calculated energy of the 2Z state of A10 is lower by 8.6 kcal/mol than that of the ZII state and in good agreement with the previously calculated valueZo (9.9 kcal/mol). The calculated energy of AIO(ZZ) + CO is 15.4 kcal/mol above that of the trans-type complex. From these values, the reaction A1 + C 0 2 AlO(’Z) + CO is 5.8 kcal/mol endothermic, and this value is consistent with the experimental estimation (4.5 kcal/mol: D(C-0) = 126 kcal/mol, D(A1-O) = 121.5 kcal/mol). The geometries of the transition states of the 22 and the 211 states are similar to each other except for the AlOC angle and the A10 distance. From the transition-state structures, both reactions (2Z and ZII) consequently becomes transition states, which is qualitatively consistant with the Hammond postulate.2’ The ,Z transition state correlates to the C,, complex, and the ZII transition state correlates to trans-type complex. The values of energy barriers of the products are 17.8 and 4.6 kcal/mol for the ZZ and Zll states, respectively. The ZII transition state is lower in energy by 4.6 kcai/mol than the transition state. This is explained by the fact that the 2Z state of A10 at the long A1-O distance from the equilibrium bond distance is higher in energy than the 211 state.19 Thus, both reaction surfaces possibly cross each other in the neighboring region of the transition states. Experimentally determined activation energies’*4 of the A1C02 reaction are 2.5 and 3.9 kcal/mol, while the experimentally estimated heat of reaction is about 5 kcal/mol endothermic. Therefore, the experimental activation energy is considered to be that of the reaction of the AlCO2 complex formation. The calculated activation energy of the complex formation is 2.3 kcal/mol
2,240 citations
TL;DR: In this article, the authors used time, wavelength, temperature, and polarization-resolved luminescence to elucidate the nature of absorbing and band edge states in 32 A diameter wurtzite CdSe quantum crystallites.
Abstract: We use time‐, wavelength‐, temperature‐, polarization‐resolved luminescence to elucidate the nature of the absorbing and ‘‘band edge’’ luminescing states in 32 A diameter wurtzite CdSe quantum crystallites. Time‐resolved emission following picosecond size‐selective resonant excitation of the lowest excited state shows two components—a temperature insensitive 100 ps component and a microsecond, temperature sensitive component. The emission spectrum, showing optic phonon vibrational structure, develops a ∼70 wave number red shift as the fast component decays. Photoselection shows the slow component to be reverse polarized at 10 K, indicating this component to be the result of a hole radiationless transition. The 100 ps emitting state is repopulated thermally as temperature increases from 10 to 50 K. All available data are interpreted by postulating strong resonant mixing between a standing wave molecular orbital delocalized inside the crystallite and intrinsic surface Se lone pair states. The apparent excit...
727 citations
TL;DR: In this paper, a water-soluble complex of C60 was formed on refluxing a solution of γ-cyclodextrin with solid C60; the lifetime of the triplet excited state of the complex was 83 µs in an oxygen free solution.
Abstract: A water-soluble complex of C60 is formed on refluxing a solution of γ-cyclodextrin with solid C60; the lifetime of the triplet excited state of C60 in the complex is 83 µs in an oxygen free solution.
384 citations
01 Jan 1992
TL;DR: Theoretical concepts, models and methods for conjugated polymers have been discussed in this paper, with a focus on the properties of conjugate polymers and their properties.
Abstract: 1. Introduction.- References.- 2. An Overview of the Theory of ?-Conjugated Polymers.- 2.1 Synopsis.- 2.2 Theoretical Concepts, Models and Methods.- 2.2.1 The Born-Oppenheimer Approximation.- 2.2.2 Ab Initio Calculations.- 2.2.3 Model Hamiltonians.- 2.3 The Huckel and SSH Models: Independent-Electron Theories.- 2.3.1 From Polyethylene to Polyacetylene.- 2.3.2 Bond Alternation.- 2.3.3 The Strength of the Electron-Phonon Coupling.- 2.3.4 Stability of the Dimerized State and the Phonon Spectrum.- 2.3.5 Spatially Localized Nonlinear Excitations: Solitons, Polarons and Bipolarons.- 2.3.6 Predictions of the Model.- 2.4 Hubbard Model: A Paradigm for Correlated Electron Theories.- 2.4.1 Ground State and Excitation Spectrum.- 2.4.2 Correlation Functions.- 2.4.3 Relevance for Conjugated Polymers.- 2.5 The One-Dimensional Peierls-Hubbard Model.- 2.5.1 The Model Hamiltonian and its Parameters.- 2.5.2 Methods.- 2.6 The Combined Effects of Electron-Phonon and Electron-Electron Interactions: Theory and Experiment.- 2.6.1 Ground State.- 2.6.2 Electronic Excitations and Excited States.- 2.6.3 Vibrational Excitation: Raman and Infrared Spectroscopy.- 2.7 Beyond Simple Models: Discussion and Conclusions.- 2.7.1 Effects of Disorder.- 2.7.2 Interchain Coupling and Three-Dimensional Effects.- 2.7.3 Lattice Quantum Fluctuations.- 2.7.4 Doping Effects and the Semiconductor-Metal Transition.- 2.7.5 Transport.- 2.7.6 Concluding Remarks.- References.- 3. Charge Transport in Polymers.- 3.1 Models for the Insulating and Semiconducting States.- 3.1.1 The Electronic Ground State.- 3.1.2 The Nature of the Charge Carriers.- 3.1.3 Disorder Along the Chains.- 3.1.4 Low and Intermediate Doping.- 3.2 Models for Transport Processes.- 3.2.1 Conduction in Extended States.- 3.2.2 Conduction in Localized States.- 3.2.3 Transport in One Dimension.- 3.2.4 Transport by Quasi-Particles.- 3.3 Experiments in the Insulating and Semiconducting State.- 3.3.1 Polyacetylene.- 3.3.2 Other Polymers.- 3.4 The Semiconductor-Metal Transition and the Metallic State.- 3.4.1 Models for the Highly Doped State.- 3.4.2 Experiments in the Highly Doped State.- 3.5 Summary.- References.- 4. Optical Properties of Conducting Polymers.- 4.1 Elementary Considerations.- 4.2 Dielectric Response Function and Band Structure.- 4.3 Band Gap and Band Structures of Undoped Conjugated Polymers.- 4.3.1 Results of Band Structure Calculations.- 4.3.2 Experimental Results.- 4.4 Photon-Phonon Interaction.- 4.4.1 General Remarks.- 4.4.2 Calculations of Vibrational Spectra of Polymers.- 4.4.3 Experimental Results.- 4.5 The Study of Elementary Excitations in Conjugated Polymers.- 4.5.1 General Considerations.- 4.5.2 The Electronic States of the Quasi-Particles.- 4.5.3 The Vibrational State of the Quasi-Particles.- 4.5.4 Experimental Results.- 4.6 Highly Conducting Conjugated Polymers.- 4.6.1 General Considerations.- 4.6.2 The Highly Conducting Phase of Trans-Polyacetylene.- 4.6.3 Polyacetylene: Experimental Results.- 4.6.4 Highly Conducting Polymers with Nondegenerate Ground State.- 4.6.5 Concluding Remarks.- References.- 5. Magnetic Properties of Conjugated Polymers.- 5.1 General Aspects of Magnetic Properties and Resonance Techniques.- 5.1.1 Susceptibility.- 5.1.2 Lineshapes, Linewidths and Lineshifts.- 5.1.3 Spin Relaxation (T1,T2,T1p).- 5.1.4 Double Resonance Techniques.- 5.1.5 High-Resolution NMR.- 5.2 Structure and Lattice Dynamics of Conjugated Polymers in the Non-Conducting Phase.- 5.2.1 Lattice Structure Determination from Dipole-Dipole Interactions.- 5.2.2 Bond Length Determination from Dipole-Dipole Interactions.- 5.2.3 Chemical Shift Tensor.- 5.3 Spin Dynamics of Conjugated Defects in the Non-Conducting Phase.- 5.3.1 ESR and ENDOR Lineshapes.- 5.3.2 Dynamic Nuclear Polarization.- 5.3.3 Nuclear Spin Lattice Relaxation.- 5.3.4 Electron Spin Relaxation.- 5.3.5 Light-Induced ESR.- 5.4 Magnetic Properties of Conjugated Polymers in the Conducting Phase.- 5.4.1 Susceptibility.- 5.4.2 ESR Lineshapes and Linewidths.- 5.4.3 NMR Results.- 5.5 Magnetic Properties of Polydiacetylenes (PDA).- 5.5.1 Structure.- 5.5.2 Solid-State Polymerization.- 5.5.3 Quasi-Particle Excitation.- 5.6 Other Conjugated Polymers.- 5.7 Conclusions and Remarks.- References.
382 citations
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
343 citations
TL;DR: In this paper, the authors examined the effects of solvation on chromophores using a simple self-consistent reaction field (SCRF) model, in which a SCRF selfconsistent field calculation is followed by configuration interaction to generate excited states in the presence of a dielectric continuum.
Abstract: We examine the effects of solvation on chromophores using a simple self-consistent reaction field (SCRF) model. In this model a SCRF self-consistent field calculation is followed by configuration interaction to generate excited states in the presence of a dielectric continuum. The absorption process is considered instantaneous, and only the electron polarization of the solvent is allowed to respond to the excited-state charge distribution. This model is then applied to a variety of molecules in «solution» using the intermediate neglect of differential overlap (INDO/S) model Hamiltonian. The model reproduces very well the shifts observed in aprotic solvents
310 citations
TL;DR: In this article, a quantum theory of photoinduced electron transfer, based on the Redfield theory of relaxation, is developed and applied to the standard two state-one mode system interacting with a thermal bath.
Abstract: A quantum mechanical theory of photoinduced electron transfer, based on the Redfield theory of relaxation, is developed and applied to the standard two state–one mode system interacting with a thermal bath. Quantum mechanical treatment of the reaction coordinate allows incorporation of both finite vibrational dephasing and energy flow rates into the description of electron transfer dynamics. The field–matter interaction is treated explicitly to properly incorporate the total energy and magnitude of the vibrational coherence present in the initially prepared state. Calculation of the reduced density matrix of the system is carried out in a vibronic basis that diagonalizes the electron exchange coupling so that the method is valid for arbitrarily large coupling strength. For weak electronic coupling, we demonstrate the equivalence between the results from Redfield theory and those obtained from the standard perturbative expression (golden rule) for nonadiabatic electron transfer. We then discuss quantitatively the breakdown of the Fermi golden rule with increasing electronic coupling strength. The failure of the golden rule is seen to result from either slow energy equilibration in the reactant or product well or from quantum interference effects resulting from finite dephasing rates. For cases where the reorganization energy is large compared to the frequency of reactive motion, such that we may ignore nuclear tunneling, results from the theory show good agreement with those from the semiclassical Landau–Zener theory when motion of the reaction coordinate through the surface crossing region can be considered to be ballistic. Finally results are shown in the weak damping (coherent) limit that demonstrate interference effects between phase coherences involving states in both wells.
289 citations
TL;DR: In this paper, a phase coherent atomic ensemble (phaseonium) is proposed for high precision magnetometry and particle acceleration, which is a new state of matter and exhibits many unusual features such as lasing without population inversion and quenching of the Schawlow-Townes quantum noise.
258 citations
TL;DR: In this article, a review of recent work on ultrafast experiments on excited state intramolecular electron and proton transfer, with an emphasis on experiments on chemical systems that have been analyzed theoretically, is presented.
Abstract: This article primarily reviews recent work on ultrafast experiments on excited state intramolecular electron and proton transfer, with an emphasis on experiments on chemical systems that have been analyzed theoretically. In particular, those systems that have been quantitatively characterized by static spectroscopy, which provides detailed information about the reaction potential energy surface and about other parameters that are necessary to make a direct comparison to theoretical predictions, are described.
255 citations
TL;DR: In this article, the core-valence correlation is introduced into ab initio relativistic pseudopotential calculations by modifying the existing core polarization potential, and the salient feature of the method presented here is the use of an l-dependent cutoff parameter (which is related to spherical harmonic functions) for solving the multicenter integrals over the 1/r4 and r/r3 type operators.
Abstract: The core–valence correlation is introduced into ab initio relativistic pseudopotential calculations by modifying the existing core polarization potential. The salient feature of the method presented here is the use of an l‐dependent cutoff parameter (which is related to spherical harmonic functions) for solving the multicenter integrals over the 1/r4 ‐ and r/r3 ‐type operators. The method is tested on the Rb2 and Cs2 molecules considered as two valence‐electron problems. Reliable results for the molecular spectroscopic constants (Re, Te, De, and ωe ) are obtained for the ground state and the lowest excited states. Deviation from the experimental values ranges from 0.05 to 0.1 A for Re, seldom exceeds 2 cm−1 for ωe, and is of the order of 100 cm−1 for De for most of the excited states.
TL;DR: A linear-response theory is presented for the thermopower of a quantum dot of small capacitance, and the periodicity of the oscillations is the same as that of the previously studied Coulomb-blockade oscillations in the conductance.
Abstract: A linear-response theory is presented for the thermopower of a quantum dot of small capacitance. In the classical regime (thermal energy kT much greater than the level spacing \ensuremath{\Delta}E), the thermopower oscillates around zero in a sawtooth fashion as a function of Fermi energy (as long as kT is small compared to the charged energy ${\mathit{e}}^{2}$/C). The periodicity of the oscillations is the same as that of the previously studied Coulomb-blockade oscillations in the conductance, and is determined by the difference in ground-state energies on addition of a single electron to the quantum dot. In the quantum regime of resonant tunneling (kT\ensuremath{\ll}\ensuremath{\Delta}E), a fine structure is predicted to develop on the oscillations. Unlike the Coulomb-blockade oscillations, the periodicity of the fine structure is determined by the excitation spectrum at a constant number of electrons on the quantum dot.
TL;DR: Under conditions of strong dipole coupling an optical cavity containing one atom behaves as a two-state system when excited near one of the ``vacuum'' Rabi resonances.
Abstract: Under conditions of strong dipole coupling an optical cavity containing one atom behaves as a two-state system when excited near one of the ``vacuum'' Rabi resonances. A coherent driving field induces a dynamic Stark splitting of the ``vacuum'' Rabi resonance. We demonstrate this two-state behavior in computer experiments based on quantum trajectory simulations.
TL;DR: In this article, the real-time dynamics of hydrogen-atom transfer processes under collisionless conditions are studied using femtosecond depletion techniques, where the authors focus on the methyl salicylate system, which exhibits ultrafast hydrogen motion between two oxygen atoms due to molecular tautomerization, loosely referred to as intramolecular proton transfer.
Abstract: The real‐time dynamics of hydrogen‐atom‐transfer processes under collisionless conditions are studied using femtosecond depletion techniques. The experiments focus on the methyl salicylate system, which exhibits ultrafast hydrogen motion between two oxygen atoms due to molecular tautomerization, loosely referred to as intramolecular ‘‘proton’’ transfer. To test for tunneling and mass effects on the excited potential surface, we also studied deuterium and methyl‐group substitutions. We observe that the motion of the hydrogen, under collisionless conditions, takes place within 60 fs. At longer times, on the picosecond time scale, the hydrogen‐transferred form decays with a threshold of 15.5 kJ/mol; this decay behavior was observed up to a total vibrational energy of ∼7200 cm−1. The observed dynamics provide the global nature of the motion, which takes into account bonding before and after the motion, and the evolution of the wave packet from the initial nonequilibrium state to the transferred form along the O–H—O reaction coordinate. The vibrational periods (2π/ω) of the relevant modes range from 13 fs (the OH stretch) to 190 fs (the low‐frequency distortion) and the motion involves (in part) these coordinates. The intramolecular vibrational‐energy redistribution dynamics at longer times are important to the hydrogen‐bond dissociation and to the nonradiative decay of the hydrogen‐transferred form.
TL;DR: In this article, all existing data on the level densities, decay widths and lifetimes of excited nuclei have been analyzed in the framework of the statistical model in order to better determine the parameters of the phenomenological systematics of the nuclear level density.
TL;DR: Rantala and Rosen as mentioned in this paper measured the vibrational energy relaxation of the internal C-O stretching mode of carbon monoxide in the c(2×2) overlayer on the Cu(100) surface at 120 K by picosecond pumpprobe spectroscopy.
Abstract: Vibrational energy relaxation of the internal C–O stretching mode of carbon monoxide in the c(2×2) overlayer on the Cu(100) surface at 120 K is measured by picosecond pump–probe spectroscopy. A resonant 1.5 ps infrared pulse at ν=2085 cm−1 pumps the C–O stretching mode. The energy relaxation is monitored by sum frequency generation from a delayed pair of 1.5 ps infrared and visible pulses. A single component decay, with a decay time of 2.0 ±0.5 ps, is reported. Uncertainties in the actual excited state lifetime are discussed, and the actual lifetime is estimated to be 2.0 ±1.0 ps. This lifetime is close to the lower limit of 1.2 ps set by the observed vibrational linewidth of 4.5 cm−1. The energy relaxation process is interpreted to occur by nonadiabatic energy transfer to the electrons (electron‐hole pair excitations) of the copper substrate, and the measurement supports previous assertions that the nonadiabatic energy transfer rate for this system is very rapid. The nonadiabatic energy transfer lifetime of this mode has previously been estimated by density‐functional calculations [T. T. Rantala and A. Rosen, Phys. Rev. B 34, 837 (1986)], and has recently been calculated by extrapolation of ab initio Hartree–Fock electronic structure calculations for CO on copper clusters [M. Head‐Gordon and J. Tully, preceding paper, J. Chem. Phys. 96, 3939 (1992)]. The calculated lifetimes in both cases are in the 1–3 ps range, in good agreement with the experimentally measured value.
TL;DR: The 351 nm photoelectron spectra of the phenide, benzyl and phenoxide anions are reported in this paper. But the results are limited to the presence of two vibrational modes at 600(10) and 968(15) cm −1, and an excited electronic state at ⩽ 1.7 eV.
TL;DR: It is observed that new transport erects in lateral quantum dots where zero-dimensional (OD) states and single electron charging coexist, and in linear transport coherent resonant tunneling is seen, described by a Landauer formula despite the many-body charging interaction.
Abstract: We observe new transport erects in lateral quantum dots where zero-dimensional (OD) states and single electron charging coexist. In linear transport we see coherent resonant tunneling, described by a Landauer formula despite the many-body charging interaction. In the nonlinear regime, Coulomb oscillations or a quantum dot with about 25 electrons show structure due to OD excited states as the bias voltage increases, and the current-voltage characteristic has a double-staircase shape
TL;DR: In this paper, a computational scheme is proposed for ab initio calculations of electronic spectra of molecular systems, which is based on the different effects that determine the excitation energies and properties of the excited states.
TL;DR: In this paper, experiments utilizing laser-driven three-level Λ systems are devised whose outcomes differ qualitatively depending on the presence or absence of such a spontaneous generation of coherence.
Abstract: Spontaneous decay of an excited atomic state may give rise to a coherent superposition of two recipient states. Experiments utilizing laser-driven three-level Λ systems are devised whose outcomes differ qualitatively depending on the presence or absence of such a spontaneous generation of coherence.
TL;DR: In this paper, the ground state of the alternating spin 1/2 Heisenberg chain with couplings J(> 0) and J′ is studied and the behavior of the string order and energy gap indicates that the ground states over the whole range −∞ ≤ J′< J can be regarded as a single phase.
Abstract: The ground state of the alternating spin 1/2 Heisenberg chain with couplings J(> 0) and J′ is studied. This model interpolates the S=1 and S=1/2 antiferromagnetic Heisenberg chains continuously. The behavior of the string order and energy gap indicates that the ground state over the whole range −∞ ≤ J′< J can be regarded as a single phase. The physical picture of the ground state and the first excited state is also discussed.
TL;DR: In this paper, a nonempirical theory of vibrational relaxation at metal surfaces via nonadiabatic coupling to conduction electrons is presented using a single determinant Hartree-Fock (HF) description of the electronic states of the system, an expression for the lifetime of an excited vibration is obtained.
Abstract: A nonempirical theory of vibrational relaxation at metal surfaces via nonadiabatic coupling to conduction electrons is presented. Using a single determinant Hartree–Fock (HF) description of the electronic states of the system, an expression for the lifetime of an excited vibration is obtained. Under certain additional assumptions, all the quantities necessary to calculate the lifetime can be obtained from the results of ab initio HF calculations on cluster models of the adsorbate‐metal system. As a practical test of this procedure, the lifetime of the excited v=1 vibrational state of CO on Cu(100) is calculated using clusters of 6, 10, and 14 copper atoms. Results ranging between 1.1 and 3.5 ps are obtained, with our preferred procedure yielding 1.7 ps for the largest cluster, in good agreement with experiment. Extensions of this approach may also be valuable for treating other nonadiabatic phenomena at metal surfaces.
01 Jun 1992
TL;DR: In this paper, the authors examined intramolecular proton transfer in 2-(2′-hydroxyphenyl)benzoxazole in its electronic S 1 state.
Abstract: We examine intramolecular proton transfer in 2-(2′-hydroxyphenyl)benzoxazole in its electronic S 1 state. The experimental methods are fluorescence spectroscopy of the compound isolated in an argon matrix at 11 K and in a supersonically cooled jet, as well as femtosecond pump-and-probe spectroscopy in cyclohexane at 298 K. From the spectroscopic measurements we conclude that the vibronic bands near the electronic origin have a homogeneous width ⩾ 150 cm −1 , corresponding to a vibronic lifetime of less than 35 fs. Residual structure reveals a short progression in a vibrational mode of 147 cm −1 . The time-resolved measurements indicate a short-lived initial Franck-Condon distribution which evolves, with a time constant of 60±30 fs, into a distribution of vibrational levels which partly belong to the excited keto form of the molecule. The molecular geometries of the excited enol and keto forms are calculated using MNDO methods. For these geometries, the positions of the mobile hydrogen atom are separated by 0.41 A. We construct a model potential for excited-state intramolecular proton transfer which is consistent with the observations.
TL;DR: The photodissociation of water in the first absorption band, H{sub 2}O(X) + {Dirac_h}{omega} {yields} H[sub 2]O(A{sup 1}B{sub 1} + OH{sup 2}S] + OH[sup 2]II], is a prototype of fast and direct bond rupture in an excited electronic state.
Abstract: The photodissociation of water in the first absorption band, H{sub 2}O(X) + {Dirac_h}{omega} {yields} H{sub 2}O(A{sup 1}B{sub 1}) {yields} H({sup 2}S) + OH({sup 2}II), is a prototype of fast and direct bond rupture in an excited electronic state. It has been investigated from several perspectives-absorption spectrum, final state distributions of the products, dissociation of vibrationally excited states, isotope effects, and emission spectroscopy. The availability of a calculated potential energy surface for the A state, including all three internal degrees of freedom, allows comparison of all experimental data with the results of rigorous quantum mechanical calculations without any fitting parameters or simplifying model assumptions. As the result of the confluence of ab initio electronic structure theory, dynamical theory, and experiment, water is probably the best studied and best understood polyatomic photodissociation system. In this article we review the joint experimental and theoretical advances which make water a unique system for studying molecular dynamics in excited electronic states. We focus our attention especially on the interrelation between the various perspectives and the correlation with the characteristic features of the upper-state potential energy surface. 80 refs., 14 figs.
TL;DR: The chromophore-quencher properties of α-diimine rhenium tricarbonyl complexes [LnMRe(CO)3(α)-diimines as mentioned in this paper have been shown to be related to those of binuclear metal-metal bonded complexes.
Abstract: α-Diimine rhenium tricarbonyl complexes [(L)Re(CO)3(α-diimine)]α/+ are exceptional among organometallic complexes in showing emission from their MLCT states at room temperature in fluid solution. The properties of these states can be “fine-tuned” by variation of the α-diimine and co-ligand L, the solvent and the rigidity of the medium. Light-induced energy and electron transfer processes occur inter- and intramolecularly. Reductive quenching of the MLCT state leads to a charge-separated LLCT state. The excited state properties of these chromophore-quencher complexes seem to be related to those of the binuclear metal-metal bonded complexes [LnMRe(CO)3(α-diimine)] (LnM = metal fragment).
TL;DR: It is proposed that the dependence is indicative of the resonant inelastic scattering description of these emission spectra, i.e., the absorption-emission process should be described as a single scattering event where the momenta of the photoelectron and the valence hole in the final state are related by momentum conservation.
Abstract: We present carbon K emission spectra of diamond excited with high-resolution undulator radiation The valence-band emission spectra are shown to be strongly dependent on the excitation energy, up to 20--30 eV above the C K edge It is proposed that the dependence is indicative of the resonant inelastic scattering description of these emission spectra, ie, the absorption-emission process should be described as a single scattering event where the momenta of the photoelectron and the valence hole in the final state are related by momentum conservation
TL;DR: In this article, both pulse radiolysis and laser flash photolysis techniques have been employed to characterize the triplet excited state behavior of C 60 and C 70 in benzene at 296 K.
Abstract: Both pulse radiolysis and laser flash photolysis techniques have been employed to characterize the triplet excited state behavior of C 60 and C 70 in benzene at 296 K. Apart from the previously reported absorption in the visible, we were able to characterize its absorption in the UV region and determine the extinction coefficients in the visible region. Pulse radiolysis experiments give indirect confirmation for the spectral features of the triplet excited states
TL;DR: The photoproperties of main group metal complexes with the electron configurations s2 (e.g. Tl+, Sb3+, Te4+) were studied on the basis of a general concept which relates characteristic excited states to typical photophysical and photochemical processes as mentioned in this paper.
Abstract: The photoproperties of main group metal complexes with the electron configurations s2 (e.g. Tl+, Sb3+, Te4+) and so (e.g. T13+, Pb4+) were studied on the basis of a general concept which relates characteristic excited states to typical photophysical and photochemical processes. The photochemistry is dominated by metal- centered sp (s2) and ligand to metal charge transfer (so) excited states which are capable of inducing inter- and intramolecular redox reactions.
TL;DR: In this article, a time-resolved differential transmittance measurement at 568, 620, and 656 nm reveals oscillations from coherent vibrational motion of the retinal chromophore as well as timedependent changes reflecting its excited state dynamics and subsequent photochemistry.
TL;DR: In this paper, the transition energies for ethylene have been calculated via configuration interaction including all singly excited configurations (CIS) using a variety of basos sets, and the minimum requirement for a satisfactory basis set is 6-311 (2+)G * having two sets of diffuse functions on the carbon atoms.
Abstract: The transition energies for ethylene have been calculated via configuration interaction including all singly excited configurations (CIS) using a variety of basos sets. The minimum requirement for a satisfactory basis set is 6-311 (2+)G * having two sets of diffuse functions on the carbon atoms. The excited states were examined via charge density difference plots. The CIS and MP2-corrected CIS (CIS-MP2) methods provided good agreement with experiment for both vertical and adiabatic energies