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Showing papers on "Excited state published in 1981"


Journal ArticleDOI
TL;DR: The available rate data on the reactivity and physical deactivation of molecular oxygen in its first electronic excited state (1Δg) in liquid solution have been critically compiled as discussed by the authors.
Abstract: The available rate data on the reactivity and physical deactivation of molecular oxygen in its first electronic excited state (1Δg) in liquid solution have been critically compiled. Where possible, relative rates reported in the literature have been normalized to standard values selected by a statistical analysis of the experimental data. Second order rate constants for the deactivation and chemical reaction of singlet oxygen are reported for 670 compounds. Additionally, psuedo first order rate constants (kd) for solvent deactivation of singlet oxygen are reported for 50 different solvents.

555 citations


Journal ArticleDOI
TL;DR: In this article, a review of recent theoretical studies on the quasiperiodic and chaotic dynamical aspects of vibrational states and how those studies may be related to intramolecular randomization is presented.
Abstract: The extent and rate of intramolecular energy transfer play a role in a variety of problems in chemical dynamics. Examples are unimolecular reactions (1 a,b), chemical activation (2a,b), vibrational-rotational-translation energy distribution of the products of a dissociating species (3, 4), infrared multiphoton decomposition of molecules (5a,b, 6), internal conversion and intersystem crossing of electronically excited states (7a-d), dissociation of vibrationally excited state-selected van der Waals complexes (8), fluorescence spectra of electronically and vibrationally excited molecules (9a,b, 10a,b), chemiluminescent spectra of vibrationally excited molecules (11), reactions induced by excitation of high overtones of a bond vibration (12a-c), and high overtone spectra (13a,b). The present article reviews recent theoretical studies on the quasiperiodic and chaotic dynamical aspects of vibrational states and describes how those studies may be related to intramolecular randomization.

363 citations


Journal ArticleDOI
TL;DR: In this paper, Bounds and Siebrand showed that the electron-hole pair binding energy decreases faster than rCT−1 with increasing separation and explained the high carrier generation efficiency in pentacene.

354 citations



Journal ArticleDOI
K. Emrich1
TL;DR: In this paper, the expS method is extended to excited states of finite and infinite systems and the authors obtain equations which are formally similar to the known ground-state equations of expS theory, which is applicable to Fermi as well as Bose systems.

276 citations


Journal ArticleDOI
TL;DR: A simplified theory of enhanced ultraviolet, visible, and infrared photochemistry near rough dielectric and metallic surfaces is described and numerically investigated in this paper, where the model incorporates dipole-dipole coupling between absorbing molecules and the large induced dipoles created in microscopic spheres irradiated near Mie resonances.
Abstract: A simplified theory of enhanced ultraviolet, visible, and infrared photochemistry near rough dielectric and metallic surfaces is described and numerically investigated. Protrusions on a rough surface are modeled as isolated microscopic spheres. We formulate classical equations of motion for molecules interacting with electromagnetic fields and such material spheres. The model incorporates (a) dipole–dipole coupling between absorbing molecules and the large, induced dipoles created in microscopic spheres irradiated near Mie resonances, and (b) dissipative energy transfer from excited molecules to higher order (l≳1) multipole resonances in the spheres. Calculations show that substantial enhancements in photochemical yields are possible for relatively slow chemical reactions as well as fast reactions. The similarities and differences between enhanced photochemistry and surface enhanced Raman scattering (SERS) are discussed in detail. Dielectric materials for enhanced infrared photochemistry at CO2 laser wave...

251 citations


Journal ArticleDOI
15 May 1981
TL;DR: In this article, the potential curves for the ground and excited states of the chlorine molecules and its positive and negative ions have been calculated by means of the MRD-CI method, and the results at the corresponding full CI level are estimated for each state via a perturbation correction.
Abstract: Potentials curves for the ground and excited states of the chlorine molecules and its positive and negative ions have been calculated by means of the MRD-CI method. The standard AO basis employed consists of 74 functions including two atomic d and one set of s and p bond species, and the results at the corresponding full CI level are estimated for each state via a perturbation correction. Special emphasis is placed upon the treatment of Rydberg-valence mixing in this system, which phenomenon is found to be essential to the understanding of Cl2 electronic absorption spectrum. All singlet states which correlate with the lowest dissociation limit plus many others which go to ionic Cl++Cl− or Rydberg Cl+Cl asymptotes are given explicit consideration. Among the triplet species of Cl2 which dissociate into the ground state atoms only the 3Πu state is not repulsive. The calculated D0 value for the ground state is 2.455 eV compared to the experimental value of 2.475 eV, while the vertical ionization energy and electron affinity are found to be 11.48 and 2.38 eV respectively, also in very good agreement with the corresponding measured data of 11.50 and 2.51 ± 0.1 eV. In addition to Cl2 laser line is confirmed to result from a 3Πg → 3Πu emission, whereby the calculated downward vertical transition energy of 4.86 eV fits in quite well with the known location of this line at 4.805 eV. The first two dipole-allowed transitions from the ground state of chlorine involve 1Σu+ and 1Πu states which are calculated to be nearly isoenergetic, and these results also match very well with the location of the first absorption band in this spectrum. Finally quite similarly as in O2 it is found that an avoided crossing between Rydberg and valences states produces a relatively steep potential well for an upper state (2 1Σu+), whose location concides with that of a second absorption band recently observed in synchrotron radiation studies.

241 citations


Journal ArticleDOI
TL;DR: In this paper, a highly excited (Rydberg) atom bathed in blackbody radiation is perturbed in two ways: a dynamic Stark shift is induced by the off-resonant components of the black body radiation.
Abstract: A highly excited (Rydberg) atom bathed in blackbody radiation is perturbed in two ways. A dynamic Stark shift is induced by the off-resonant components of the blackbody radiation. Additionally, electric-dipole transitions to other atomic energy levels are induced by the resonant components of the blackbody radiation. This depopulation effect shortens the Rydberg-state lifetime, thereby broadening the energy level. Calculations of these two effects in many states of hydrogen, helium, and the alkali-metal atoms Li, Na, K, Rb, and Cs are presented for $T=300$ K. Contributions from the entire blackbody spectrum and from both discrete and continuous perturbing states are included. The accuracy is considerably greater than that of previous estimates.

224 citations


Journal ArticleDOI
TL;DR: In this article, a density matrix formalism is used to describe a highly excited part formed by a collision and the coalescence volume is found to be related to the internal wave function of the composite particle and the spatial distribution of nucleons.

213 citations


Journal ArticleDOI
TL;DR: In this paper, a series of highly exothermic reactions of tris(bipyridyl) complexes involving electronically excited reactants is discussed with regard to the possible importance of quantum effects and of alternate reaction pathways in understanding the failure of the series of reactions to exhibit pronounced "inverted" behavior.
Abstract: Quantum effects in outer-sphere electron transfer reactions in the inverted region are considered. The results of quantum, “semiclassical”, and classical calculations on model systems are presented. A series of highly exothermic reactions of tris(bipyridyl) complexes involving electronically excited reactants is discussed with regard to the possible importance of quantum effects and of alternate reaction pathways in understanding the failure of the series of reactions to exhibit pronounced “inverted” behavior. Electronically excited products or alternate atom-transfer mechanisms provide possible explanations for the large discrepancy.

181 citations


Journal ArticleDOI
TL;DR: In this paper, the formation kinetics, excited state energy, electronic relaxation, and intrastate nuclear dynamics in electronically-vibrationally excited states of van der Waals molecules, consisting of a tetracene (T) molecule and rare gas (R) atoms, were reported.
Abstract: In this paper we report the results of an experimental study of the formation kinetics, excited‐state energetics, interstate electronic relaxation, and intrastate nuclear dynamics in electronically–vibrationally excited states of van der Waals molecules, consisting of a tetracene (T) molecule and rare‐gas (R) atoms. The TRn molecules were synthesized in seeded supersonic jets. Excited‐state energetics and dynamics of TRn molecules were explored by laser spectroscopy in supersonic expansions, interrogating the fluorescence action spectra, the energy‐resolved emission, the relative emission quantum yields, and the time‐resolved emission. Spectroscopic diagnostic methods for the identification and characterization of the chemical composition of TRn complexes involved the dependence of the spectral features on the identity of the rare gas, an intensity conservation rule for the intensities of TArn and of T, the pressure dependence of the intensity of the bare T molecule, the pressure dependence of the intensi...

Journal ArticleDOI
TL;DR: In this article, the sensitivity of Stimulated Emission Pumping (SEP) was examined by exciting the I2(B 0+u-X 1Σ+g) 17-0 P(38) line and stimulating the R(36) line of the 17-11, 17-10, and 17-9 bands.
Abstract: Stimulated emission pumping (SEP) is a new method for sub‐Doppler spectroscopy and efficient state‐selective preparation of highly excited rotational–vibrational levels of small molecules. The sensitivity of SEP has been examined by exciting the I2(B 0+u–X 1Σ+g) 17–0 P(38) line and stimulating the P(38) and R(36) lines of the 17–11, 17–10, and 17–9 bands. All observed effects when the two laser pulses were temporally separated could be accounted for by a master equation model.

Journal ArticleDOI
TL;DR: The photophysical and electron transfer properties of the lowest excited state of nine ruthenium (polypyridine) complexes have been characterized in this article, where the results show that the Ru (bpy)2(DMCH)2+ complex is expected to be a more efficient mediator than Ru(bpy)-2+3 in the water splitting reaction by solar energy.
Abstract: The photophysical and electron transfer properties of the lowest excited state of nine ruthenium (polypyridine) complexes have been characterized. The complexes studied are Ru (bpy)3-n (LL)2+n, where n varies from 0 to 3, and LL is 4, 4′-di-t-butyl-2,2′-bipyridine (DTB-bpy), 3, 3′-dimethyl-2, 2′-bipyridine (DM-bpy), or a 2, 2′-diquinolyl derivative (DMCH). The results obtained show that the Ru (bpy)2(DMCH)2+ complex is expected to be a more efficient mediator than Ru (bpy)2+3 in the water-splitting reaction by solar energy.

Journal ArticleDOI
TL;DR: When light impinges on photosynthetic material – a plant leaf, an alga or a photosynthesis bacterium – it is absorbed by an array of lightcollecting pigments, which convert light energy into chemical energy which is ultimately used in the metabolic processes of the cell.
Abstract: When light impinges on photosynthetic material – a plant leaf, an alga or a photosynthetic bacterium – it is absorbed by an array of lightcollecting pigments. Through resonant energy transfer the absorbed quantum of light is transported to a trap, the reaction centre. Within such a trap, a specialized (bacterio)chlorophyll complex is able to eject from its excited state an electron. This electron is ‘captured’ by an adjacent acceptor, which in turn donates the electron to a second acceptor, and so on. Thus, light energy is converted into chemical energy which is ultimately used in the metabolic processes of the cell.

Journal ArticleDOI
P. J. Dean, D. C. Herbert, C. J. Werkhoven1, B.J. Fitzpatrick1, R.N. Bhargava1 
TL;DR: In this paper, a tunable dye laser for relatively pure vapor and solution-grown single crystals of ZnSe was used to estimate donors in selective photoluminescence (SPL) and photolumininescence excitation (PLE) spectra.
Abstract: Accurate measurements of donors in selective photoluminescence (SPL) and photoluminescence excitation (PLE) spectra have been made with a tunable dye laser for relatively pure vapor and solution-grown single crystals of ZnSe. The donor species are identified by reference to the work of Merz et al. Very accurate agreement is found for the $1s\ensuremath{-}2s,p$ excitation energies, though not for the absolute photon energies. A new bound exciton (BE) falling just above the donor BE is shown not to involve a further donor species. Improved values are derived for effective-mass donor binding energy, the electron effective mass, static dielectric constant, internal binding energy of the free exciton (FE), and the free-particle band gap in ZnSe. Large differences in the PLE spectra of excitons bound to ionized compared with neutral donors, as well as for neutral acceptors and other BE, are attributed to the dominance of free electron-hole pairs in the excitation channel for the former and FE for the latter luminescence. Landau-level effects appear in the PLE for ionized donor luminescence. New excited BE states appearing just below the $n=2$ FE energies are shown by SPL to involve neutral donors. Their wave-function character is contrasted with the donor bound-exciton excited states just below the $n=1$ FE. The nature of splittings observed in ionized donor BE is discussed.

Journal ArticleDOI
TL;DR: Two-photon absorption is used to populate the 3p 3 P state of O and the 2s 2 2p 2 3p 4 D o state of N in a flow discharge as mentioned in this paper.

Journal ArticleDOI
TL;DR: The results of experimental and theoretical studies of chemical reactions in nonequilibrium plasmas are reviewed in this article, with special attention given to processes stimulated by vibrational excitation of the ground electronic state of the reacting molecules in the plasma.
Abstract: The results of experimental and theoretical studies of chemical reactions in nonequilibrium plasmas are reviewed. Special attention is given to processes stimulated by vibrational excitation of the ground electronic state of the reacting molecules in the plasma. General patterns in the kinetics of these reactions are discussed, and the optimum discharge parameters for maximum energy efficiency are noted. Specific plasma-chemical processes—the dissociation of CO2 and H2O and the synthesis of nitrogen oxides—are described. Experimental results are presented for hf, microwave, glow, plasma-beam, and non-self-sustained discharges, for plasma radiolysis, etc.

Journal ArticleDOI
TL;DR: In this paper, a measurement based on the fast-atomic-beam separated-oscillatory field method of sub-natural-linewidth spectroscopy gives, for the Lamb shift in hydrogen, $\mathcal{S}(n=2)=1057.845(9)$ MHz.
Abstract: A measurement based on the fast-atomic-beam separated-oscillatory-field method of sub-natural-linewidth spectroscopy gives, for the Lamb shift in hydrogen, $\mathcal{S}(n=2)=1057.845(9)$ MHz. The result is not in good agreement with theory.

Journal ArticleDOI
TL;DR: In this paper, the Auger electron transition in solids is discussed under the aspect of a local excitation due to the strongly localized primary hole in an inner atomic core level, where the solid is represented by a cluster model, consisting of the excited atom and its neighbors.

Journal ArticleDOI
TL;DR: In this article, the modulation depth and lifetime were measured for quantum beats observed in the fluorescence decay of anthracene in the AIP (AIP) system. But the modulation length was not measured.
Abstract: The modulation depth and lifetime were measured for quantum beats observed in the fluorescence decay of anthracene. (AIP)

Journal ArticleDOI
TL;DR: In this article, the authors present a flexible theory based on a full multiple scattering cluster calculation, which can be used to extract such information in ordered, disordered and other complex systems now being studied using synchrotron radiation.

Journal ArticleDOI
TL;DR: A two-line laser-excited fluorescence technique has been developed to measure the rotational temperature of the OH molecule, eliminating problems encountered in the application of other laser fluorescence methods for measuring the OH temperature in combustion environments.
Abstract: A two-line laser-excited fluorescence technique has been developed to measure the rotational temperature of the OH molecule. This technique eliminates problems encountered in the application of other laser fluorescence methods for measuring the OH temperature in combustion environments, such as fluorescence trapping, nonequilibrium excited state population, spectral bandwidth sensitivity, and quenching. The technique consists of exciting a specific rotational level of the OH molecule in the A(2)Sigma (upsilon' = 0) excited state from two different rotational levels in the X(2)Pi(upsilon'' = 0) ground state using a tunable dye laser and monitoring the broadband fluorescence. An example of the implementation of this technique in an atmospheric pressure methane-air flat flame is included. The possible application of this technique in turbulent combustion is also evaluated.

Journal ArticleDOI
TL;DR: In this article, the fluorescence spectra of Eu3+ activated rare earth oxychlorides (REOCl) were analyzed at 4.2, 77, and 300 K. The energy level schemes established from the spectra show a relatively strong crystal field effect.
Abstract: The fluorescence spectra of Eu3+ activated rare earth oxychlorides REOCl : Eu3+ (RE = Y, La, Gd) were recorded and analyzed at 4.2, 77, and 300 K. For each compound more than 100 transitions between the Stark levels of the 4f6 configuration were observed and assigned. The energy level schemes established from the spectra show a relatively strong crystal field effect. The five nonzero crystal field parameters for the C4v point site symmetry occupied by the rare earth ion were determined, yielding a mean square deviation of a few cm−1. The free‐ion parameters were also determined with the aid of excitation spectra. The effect of truncation of the basis set of the 2S+1LJ levels on the energy level simulation of the excited levels was also studied.

Journal ArticleDOI
TL;DR: In this article, a system composed of randomly distributed molecules, i.e., rhodamine 6G in glycerol, is experimentally investigated and time-resolved fluorescence depolarization measurements, which use a fluorescence mixing technique to give subnanosecond time resolution, provide a stringent test for theoretical work on this subject.
Abstract: Electronic excited-state transport in a system composed of randomly distributed molecules, i.e., rhodamine 6G in glycerol, is experimentally investigated. Time-resolved fluorescence depolarization measurements, which use a fluorescence mixing technique to give subnanosecond time resolution, provide a stringent test for theoretical work on this subject. The results yield an R/sub 0/ value of 50 A for R6G and confirm the results of the recent diagrammatic self-consistent theoretical method. Mean-square displacements and their time derivatives are reported. Energy transport is nondiffusive in the samples studied.

Journal ArticleDOI
TL;DR: In this paper, potential energy surfaces for the four lowest electronic states of Na (3, 2S, 3, 2P)+H2(1Σ+g) were calculated by means of the RHF-SCF and PNO-CEPA methods.
Abstract: Potential energy surfaces have been calculated for the four lowest electronic states of Na (3 2S, 3 2P)+H2(1Σ+g) by means of the RHF–SCF and PNO–CEPA methods. For the so‐called quenching process of Na (3 2P) by H2 at low initial translational energies (E–VRT energy transfer) the energetically most favorable path occurs in C2v symmetry, since—at intermediate Na–H2 separation—the ? 2B2 potential energy surface is attractive. From the CEPA calculations, the crossing point of minimal energy between the ? 2A1 and ? 2B2 surfaces is obtained at Rc = 3.57 a.u. and rc = 2.17 a.u. with an energy difference to the asymptotic limit (R = ∞, r = re) of −0.06 eV. It is thus classically accessible without any initial translational energy, but at low initial translational energies (∼0.1 eV) quenching will be efficient only for arrangements of collision partners close to C2v symmetry. There is little indication of an avoiding crossing with an ionic intermediate correlating asymptotically with Na+ and H2− as was assumed in ...


Journal ArticleDOI
TL;DR: In this article, the vibronic intensity distribution at room temperature and 77'°K of the 1'1Ag→1'1Bu transition for the series of linear polyenes with two through six conjugated double bonds has been measured and analyzed.
Abstract: The vibronic intensity distribution at room temperature and 77 °K of the 1 1Ag→1 1Bu transition for the series of linear polyenes with two through six conjugated double bonds has been measured and analyzed. These inhomogeneously broadened solution spectra can be described reasonably using only two harmonic normal modes of vibration: single and double bond stretches at ∼1200 and ∼1600 cm−1, respectively. Excited state normal coordinate displacements were determined by a least‐squares fitting procedure. For both the double and single bond modes the estimated change in bond length upon excitation decreases as the length of the polyene chain increases. The bandwidth of these spectra decreases with increasing polyene length. This is well described by assuming that in solution a range of conformations differing by very small torsions about the terminal single bonds has been frozen in. The Franck–Condon analysis indicates that under these conditions all of the polyenes are approximately planar in the 1Bu state, ruling out the argument that the lack of fluorescence in butadiene and hexatriene is due to the polyene framework being significantly twisted in the lowest energy 1Bu state.

Journal ArticleDOI
TL;DR: In this article, the Fourier transform infrared spectra of the inversion-rotation transitions have been measured with 0.010-cm −1 resolution between 40 and 300 cm −1 in the ground state and ν 2 excited states of 14 NH 3.

Journal ArticleDOI
TL;DR: The time evolution of high-energy electron distribution in an electron-beam-generated argon plasma is calculated in this article, where the distribution reaches a steady state within a very short time τ s and its shape is pressure independent for a given current density, and a given energy of the beam, the evolution time tau s being inversely proportional to the pressure.
Abstract: The time evolution of high-energy electron distribution in an electron-beam-generated argon plasma is calculated. The distribution is derived for energy values above the threshold value of the first excited state (11.56 eV) from a reduced Boltzmann equation with no electron-neutral and electron-electron collisions. This equation can be numerically solved with a continuous source term taking account of all the new plasma electrons produced over the total energy range by primary electrons. As a result, the distribution reaches a steady state within a very short time tau s and its shape is pressure independent for a given current density, and a given energy of the beam, the evolution time tau s being inversely proportional to the pressure. Moreover, the energy distributions for given beam energy and pressure are in the same ratio as the primary-electron currents. An analytical approximation for the distribution tail is given as a function of the beam parameters (energy and current) and may be used for an electron-beam-generated Ar plasma as soon as these parameters are known. The branching ratios for energy deposition with electron-beam energy ranging between 103 and 106 eV is calculated. The relative influence of primary and secondary electrons is also discussed.

Journal ArticleDOI
TL;DR: In this paper, a single vibronic level fluorescence of the C2H3O radical was reported, and the 0-0 band of the fluorescence lies at 28.798 cm−1 (347.2 nm).
Abstract: Laser‐induced single vibronic level fluorescence of the C2H3O radical is reported. The 0–0 band of the fluorescence lies at 28 798 cm−1 (347.2 nm). The C–O and C–C stretching, and the C–C–O bending vibrational energies are 1560, 1150, and 530 cm−1, respectively, in the ground electronic state, and 872, 1110 and 432 cm−1, respectively, in the excited state. The lifetime of the excited state is 0.8 μsec. The double bond nature of C2H3O is more dominant in the C–O bond than in the C–C bond in the ground state. The C2H3O radical is found in the C2H4+O reaction, as well as in the CH3CHO+F reaction.