Chemical Physics

The water-hydroxyl radical complex was prepared by irradiating peroxy radicals in hydrogen-doped argon matrices. The low water content of the matrices made it possible to observe the fundamental bands of the complexed water molecule. The experimental results are compared with the results from ab initio calculations. The complex rotates around the O-O axis in the matrix.

The vapor pressure isotope effect between samples of isotopically substituted ammonia, NH 3 , ND 3 and 15 NH 3 , and their mixtures was measured as a function of temperature ͑225ϽT/KϽ259͒ and mixture composition. The p(x,T) results were used to calculate the excess molar Gibbs energy function of the mixtures. The G E (x,T) data were fitted to a temperature dependent Redlich-Kister equation and compared with theoretical calculations based on a modified version of the theory of isotope effects in mixtures. The theoretical estimates are in good agreement with the experimental data, confirming the mechanisms responsible for the deviations from ideality in such ''almost ideal'' systems.

The direct l-type resonance spectrum of CF 3 CCH has been measured in the v 10 Z3 vibrational state by means of waveguide microwave Fourier transform spectroscopy in the range 8-26 GHz. Three types of direct l-type resonance transitions induced by the (DkZDlZG2) interaction could be observed: 140 transitions following the DJZ0, DkZDlZG2, DjljZ0, selection rule covering values of JZ17-61 and GZjkKlj from 1 to 7, 94 transitions following the DJZ0, DkZDlZG2, DjljZG2, selection rule covering values of JZ26-57 and G from 15 to 24, 90 transitions following the DJZ0, DkZDlZG4 selection rule covering values of JZ34-80 and G from 3 to 12 and 13 transitions following the DJZ0, DkZDlZG6, kZH1, lZH15kZG5, lZG3 selection rule for JZ71-83. 14 A 1-A 2 splitting transitions with klZC1 were measured from JZ33 to 49. Strong perturbations due to D(kKl)ZG3 interactions made possible the observation of perturbation-allowed transitions with selection rule kZG4, lZG35kZG3, lZH1. Furthermore, the rotational transitions JZ2-1, 3-2 and 4-3 have been measured. To make use of the multiple fitting concept, the theory of reduction developed for the v t Z2 vibrational state by Sarka and Harder [K. Sarka, H. Harder, J. Mol. Spectrosc. 197 (1999) 254] has been extended to the v t Z3 vibrational state including terms up to H 62. Owing to problems in the reproduction of data with low K and A 1-A 2 symmetry, two types of fits have been performed using five reduced forms of the effective Hamiltonian. The first type of fit used a reduced data set for which part of the transitions has been omitted. The unitary equivalence of the determined parameter sets has been demonstrated including newly derived relations for parameters in v 10 Z3. In the second type of fit, the complete data set has been included, yielding satisfactory results only in one reduction. In both type of fits, parameters up to sixth order have been determined including the axial rotational constant A and the Coriolis constant Az for both values of l. General features of the direct l-type resonance spectrum in a v t Z3 level are discussed.

Ab inifio calculations are used to provide bond lengths, harmonic frequencies, and dissociation energies of low-lying electronic states for LiX, LiX+, and LiX-(with X = Li through F and Na through Cl). Most of these species represent hitherto experimentally unknown molecules or ions, which provides the focus of the work presented here. All of these species are stable to dissociation and the anions are stable to loss of an electron. Differences among the electronic structures of the valence isoelectronic LiX; and HX, LiX+, and HX+; and LiX-and HXspecies are analyzed. Optimized geometries, dissociation energies, ionization potentials, and electron affinities were calculated for the following ground states of the respective species: rZ+ for Li2('1:)

For decades the Vogel-Fulcher-Tammann equation has dominated the description of dynamics of the non-Arrhenius behavior in glass forming systems. Recently, this dominance has been questioned. Hecksher et al. [Nat. Phys. 4, 737 (2008)], Elmatad et al. [J. Phys. Chem. B 113, 5563 (2009)], and Mauro et al. [Proc. Natl. Acad. Sci. U.S.A . 106, 19780 (2009)] indicated superiority of several equations showing no divergence at a finite (nonzero) temperature. This paper shows distortionsensitive and derivative based empirical analysis of the validity of leading equations for portraying the previtreous evolution of primary relaxation time.

We present a method for estimating the hopping rate for Zwanzig's model of self-diffusion in liquids ͓R. Zwanzig, J. Chem. Phys. 79, 4507 ͑1983͔͒. To obtain this estimate, we introduce the cage correlation function which measures the rate of change of atomic surroundings, and associate the long-time decay of this function with the basin hopping rate for diffusion. Results from a set of simulations on Lennard-Jones particles are presented. A simple analytic model for the diffusion constant in supercooled and normal liquids that is based on estimates of the activation energy obtained via the cage correlation function is derived. We discuss the breakdown of Zwanzig's hopping mechanism for mass transport as well as the low temperature behavior of the self-diffusion constant on rough potential energy surfaces.

Knopp et al. ͓J. Raman Spectrosc. 31, 51 ͑2000͔͒ have recently used resonant femtosecond coherent anti-Stokes Raman spectroscopy ͑CARS͒ to prepare and probe highly excited vibrational wave packets on the ground electronic potential surface of molecular iodine. The experiment uses a sequence of three resonant femtosecond pulses with two independently variable time delays. The first two pulses act as a pump and dump sequence to create a predefined, highly excited wave packet on the ground electronic state, whose amplitude is optimized by selecting the proper pump-dump ͑Raman͒ frequency difference and varying the time delay. The third pulse promotes the pump-dump wave packet to an excited electronic state, resulting in subsequent coherent emission of light at the anti-Stokes frequency. This fully-resonant CARS signal, measured as a function of time delay between the second and third pulses, oscillates at a frequency characteristic of the pump-dump wave packet. Due to anharmonicity, this frequency is a sensitive measure of the amount of vibrational excitation. Knopp et al. observed that under certain conditions the signal exhibits pronounced beating between the pump-dump wave packet frequency and the frequency characteristic of the bottom of the ground state well. In this paper we show that these beats arise only when the final pump-dump-pump wave packet is above the excited state dissociation threshold of the molecule. We derive analytical expressions showing that under these conditions, where the polarization is short-lived, there may be strong interferences between the contributions from molecules originally in different vibrational states of the thermal ensemble. In contrast, the CARS polarization in the below threshold case is long-lived, and these interferences cancel. Numerical evaluation of the CARS signal through vibrational wave packet propagation confirms the predictions of the analytical theory and reproduces the distinctive beating pattern observed in the experiments. Additional experiments and simulations demonstrate that these interferences can be turned on or off by carefully selecting the pulse frequencies. The experiments can also be viewed from a different perspective, as an extension of the pump-dump mechanism for selective bond breaking on the ground electronic state, to a pump-dump-pump sequence for selective bond breaking on the excited electronic state.

Density functional theory computations for a realistic model of the HIV-1 integrase active-site/substrate complex support a single-step reaction for the hydrolysis of phosphodiester bonds, which involves a highly structured S N 2-like transition state. Mediation by a stable penta-coordinated intermediate (i.e., the long time postulated dianionic phosphorane) seems lacking. These results call for an energetically favoured divalent cation requiring process coupled to a highly cooperative mechanism, which reduces the activation energy and directs the selectivity for (3 0)O-P bond hydrolysis.

Adiabatic singlet-triplet gap of the oxyallyl diradical has been studied by multireference Brillouin-Wigner and Mukherjee's coupled cluster methods (BWCC and MkCC). The results demonstrate the necessity to include connected triples excitations, as well as employing a size-extensive MRCC method. The best result, calculated at the MkCCSD(T u)/cc-pVQZ level, is in an excellent agreement with both experiment and recent spin-flip EOMCCSD(dT) calculations.

A novel method, based on genetic algorithms, has been developed and applied to the solution of di erential equations. The new approach is based on the use of real numbers to form the candidate solutions which are improved iteratively by a suitable breeding process. The algorithm was tested in the calculation of the bound states of a double well potential and in the nonlinear density functional calculation. Comparison of the results with those obtained using the direct relaxation method shows excellent agreement.

Various configurations were investigated to find the most stable structures of glycine-(water) 3 complex. Five different optimized conformers of glycine-(water) 3 complex are obtained from density functional theory calculations using 6-311ϩϩG* basis set. Relaxation energy and many body interaction energies ͑two, three, and four body͒ are also calculated for these conformers. Out of the five conformers, the most stable conformer has the BSSE corrected total energy Ϫ513.917 967 7 Hartree and binding energy Ϫ27.28 Kcal/mol. It has been found that the relaxation energies, two body energies and three body energies have significant contribution to the total binding energy whereas four body energies are very small. The chemical hardness and chemical potential also confirmed the stability of the conformer having lowest total energy.

et articulaire La paralysie cérébrale (PC) est un trouble du mouvement et de la posture due à une lésion cérébrale précoce. La comparaison clinique des données AQM, représentatives de la désorganisation motrice, avec une population saine pourrait baisser les interprétations des conséquences primaires des troubles neurologiques de celles secondaires et compensatoires résultant des anomalies musculaires et la croissance osseuse. Dans une perspective d'améliorer des traitements appropriés dans la prise en charge des PC, cette étude propose d'évaluer les conséquences directes d'une imitation des postures pathologiques sur la cinétique et les signaux EMG afin de donner un éclaircissement sur les différences entre les conséquences primaires spécifiques au PC et celles causés par des contraintes biomécaniques articulaires. Dix adultes sains ont imité deux marches pathologiques spécifiques aux PC, la marche en « jump » et la marche en « crouch ». Une AQM, avec le protocole d'Hélène Hayes, a été réalisée avec 13 caméras Vicon et deux plate-formes de forces. Les activités musculaires ont été recueillies avec le système électromyographique Noraxon. Les données spatiotemporelles, la cinématique, la cinétique et l'activation musculaire ont été recueillies pour la marche normale et les marches imitées. Comparés à la marche normale, les résultats des marches simulées ont montré la présence de perturbations significatives au niveau des paramètres spatiotemporels, de la cinétique et des activations musculaires, similaires à ceux observés chez les patients PC. Les résultats ont montré que la vitesse, la longueur du pas, la cadence et l'amplitude du mouvement ont diminué significativement. Des anomalies ont été détectées au niveau de l'activité musculaire et des moments articulaires. Comparés aux activités EMG normales, des activations musculaires prématurées et/ou des activations musculaires prolongées ont été détectées selon les spécificités de la marche simulée. Ces observations permettent de valider le fait que certaines réponses musculaires anormales détectées lors de la marche de patients PC relèvent bien souvent de contraintes biomécaniques plus que du fonctionnement anormal du muscle résultant de la lésion cérébrale. Cette étude préliminaire est un point de réflexion pour mieux appréhender les évaluations cliniques et les choix thérapeutiques. Remerciement Ce projet est financé par la région Picardie.

Screening of a macroion such as a charged solid particle, a charged membrane, double helix DNA or actin by multivalent counterions is considered. Small colloidal particles, charged micelles, short or long polyelectrolytes can play the role of multivalent counterions. Due to strong lateral repulsion at the surface of macroion such multivalent counterions form a strongly correlated liquid, with the short range order resembling that of a Wigner crystal. These correlations create additional binding of multivalent counterions to the macroion surface with binding energy larger than kBT . As a result even for a moderate concentration of multivalent counterions in the solution, their total charge at the surface of macroion exceeds the bare macroion charge in absolute value. Therefore, the net charge of the macroion inverts its sign. In the presence of a high concentration of monovalent salt the absolute value of inverted charge can be larger than the bare one. This strong inversion of charge can be observed by electrophoresis or by direct counting of multivalent counterions.

We calculate by molecular dynamics the optical functions of MgO in the far infrared region 100-1000 cm −1 , for pressures up to 40 GPa and temperatures up to 4000 K. An ab initio parametrized many-body force field is used to generate the trajectories. Infrared spectra are obtained from the time correlation of the polarization, and from Kramers-Kronig relations. The calculated spectra agree well with experimental data at ambient pressure. We find that the infrared absorption of MgO at CO 2 laser frequencies increases substantially with both pressure and temperature and we argue that this may explain the underestimation, with respect to theoretical calculations, of the high-pressure melting temperature of MgO determined in CO 2 laser-heated diamond-anvil cell experiments.

Potential energy hypersurfaces ͑PES͒ have been constructed for the ground electronic state of H 2 S utilizing results from state-of-the-art ab initio quantum chemical methods, most notably higher-order coupled cluster theory employing ͑core-polarized͒ correlation-consistent basis sets. Small corrections due to extrapolation to the complete basis set and full configuration interaction limits, core correlation, and relativistic corrections, as well as effects beyond the Born-Oppenheimer approximation have been investigated and incorporated into the final PES. Using the exact rovibrational kinetic energy operator rovibrational energy levels have been computed with the different PESs. The final converged ab initio PES of this study reproduces the available vibrational band origins of H 2 32 S, HD 32 S, D 2 32 S, and H 2 34 S with maximum deviations, gradually increasing for increased vibrational excitation, of 29͑14 300͒, 10͑3800͒, 7͑4600͒, and 12͑6400͒ cm Ϫ1 , respectively, where the maximum energy above the zero-point energy is given in parentheses. The errors are considerably larger for the bending states than for the stretching states. Reproduction of rotational term values, given explicitly for Jϭ17 of the vibrational ground state, shows remarkable agreement between experiment and the purely ab initio approach of this study.

The coexistence curve of the 2-butanol+water system has been measured at Pz 1 bar, with a higher precision and a more detailed description of the pinch-off region than in previous experimental studies. The data points in the vicinity of the UCST have been fitted to a simple scaling expression to obtain the critical point coordinates and an estimation of the range of validity of simple scaling. The experimental binodal has been used to test two king-like models including directional interactions: an asymmetric decorated lattice one and a lattice-gas model with fluctuating orientational degrees of freedom. Both models offered comparable results when a symmetrized composition variable was used.

Using small angle x-ray scattering, we find that the correlation length of bulk liquid water shows a steep increase as temperature decreases at subzero temperatures (supercooling) and that it can, similar to the thermodynamic response functions, be fitted to a power law. This indicates that the anomalous properties of water are attributable to fluctuations between low- and high-density regions with rapidly growing average size upon supercooling. The substitution of H2O with D2O, as well as the addition of NaCl salt, leads to substantial changes of the power law behavior of the correlation length. Our results are consistent with the proposed existence of a liquid-liquid critical point in the deeply supercooled region but do not exclude a singularity-free model.

This work represents the first step of a theoretical study aiming at explicitly including solvation in the CS INDO CI calculations of ground and excited state properties of organic dyes. The reported theoretical treatment falls within the electrostatic continuum theories and introduces solute–solvent interaction in the SCF calculation according to Klopman's solvaton model. The procedure was tested on two merocyanines characterized by opposite solvatochromic behaviours. It was found that solvaton systems most suitable for π-conjugated donor–acceptor dyes, like merocyanines, can be built from the net π-electron charges. The results show that the combined solvaton/CS INDO scheme is able to describe rather well the modifications of both geometries and absorption spectra of merocyanines as a function of the medium polarity. The advantages of the proposed approach with respect to other semi-empirical procedures are discussed.

Pronounced electron-phonon coupling is observed for the 2 F 7/2 ↔ 2 F 5/2 4 f transitions of Yb 3ϩ doped into CsCdBr 3 . A comparison of the Raman spectrum and the luminescence excitation sideband accompanying the 2 F 7/2 (0)→ 2 F 5/2 (2Ј) crystal-field transition reveals vibrational properties of the ͓YbBr 6 ͔ coordination unit that differ markedly from those of the CsCdBr 3 host. In particular, the vibronic transition associated with the totally symmetric ͓YbBr 6 ͔ stretching mode appears as a very weak feature at 191 cm Ϫ1 in the Raman spectrum, whereas the totally symmetric ͓CdBr 6 ͔ stretching mode of the CsCdBr 3 bulk, which appears as a strong feature at 162.5 cm Ϫ1 in the Raman spectrum, is only weakly discernible in the sideband. This is direct evidence for a large contribution from ͓YbBr 6 ͔ local modes and a small contribution from bulk modes to the vibronic intensity. The intensity of the local mode is enhanced by approximately a factor of 2 in the Raman spectrum when the laser is tuned into resonance with the 2 F 7/2 (0)→ 2 F 5/2 (2Ј) absorption of Yb 3ϩ , providing direct confirmation of its assignment. The observation of the first and second members of a Franck-Condon progression for both the local and the bulk totally symmetric modes indicates that a ⌬ process, rather than an M process, induces the vibronic intensity. Huang-Rhys factors of S local ϭ0.010Ϯ0.002 and S bulk ϭ0.15Ϯ0.03 were determined from the data, and reflect quite different electron-phonon coupling strengths. These results suggest that multiphonon relaxation of excited electronic states proceeds by the excitation of local modes of ͓YbBr 6 ͔ followed by energy transfer to bulk modes of the lattice, possibly through a nonlinear coupling mechanism which is discussed briefly.

Ab initio calculated coordinate and internal valence coordinate coefficients for each of the four spin-spin coupling surfaces of the acetylene molecule-1 J͑C, H͒, 1 J͑C, C͒, 2 J͑C, H͒, and 3 J͑H, H͒ are presented. Calculations were carried out at the SOPPA͑CCSD͒ level using a large basis set. Couplings were calculated at 35 geometries ͑including equilibrium͒ giving 35 distinct sites on the 1 J͑C, C͒ and 3 J͑H, H͒ surfaces and 53 distinct sites on the 1 J͑C, H͒ and 2 J͑C, H͒ surfaces. The results were fitted to fourth order in Taylor series expansions and are presented to second order in the coordinates. All couplings are sensitive to geometry with the principal features being ͑a͒ an even steeper increase of J͑C 1 , H 1 ͒ with CC bond stretching than with CH bond stretching-an example of ''unexpected differential sensitivity'' ͑or UDS͒, ͑b͒ very opposite variations of 2 J͑C 1 , H 2 ͒ with variations of the CC and C 2 H 2 bond lengths, ͑c͒ very opposite variations of 1 J͑C, C͒ with a CC stretch and a CH stretch and ͑d͒ very opposite variations of 1 J͑C 1 , H 1 ͒ with variations of the H 1 C 1 C 2 and C 1 C 2 H 2 angles with the latter variation being three times more effective ͑another example of UDS͒. The surfaces are averaged over a very accurate force field to give values of all couplings in the ten isotopomers containing all possible combinations of 12 C, 13 C, 1 H, and 2 H nuclei at 0 K and at a number of selected temperatures in the range accessible to experiment. The dominant nuclear motion effect comes from bending at the carbon atoms with stretching being of greater importance only for 1 J͑C, H͒. Agreement with recent experimental data both for the absolute values of the couplings and for isotope effects on them is generally very good although there are some disappointments for 1 J͑C, H͒. Values of the reduced coupling constants and their derivatives for the carbon-carbon and the one-bond carbon-proton coupling in acetylene are compared with recent results for some other molecules.

This article introduces the finite state projection ͑FSP͒ method for use in the stochastic analysis of chemically reacting systems. One can describe the chemical populations of such systems with probability density vectors that evolve according to a set of linear ordinary differential equations known as the chemical master equation ͑CME͒. Unlike Monte Carlo methods such as the stochastic simulation algorithm ͑SSA͒ or leaping, the FSP directly solves or approximates the solution of the CME. If the CME describes a system that has a finite number of distinct population vectors, the FSP method provides an exact analytical solution. When an infinite or extremely large number of population variations is possible, the state space can be truncated, and the FSP method provides a certificate of accuracy for how closely the truncated space approximation matches the true solution. The proposed FSP algorithm systematically increases the projection space in order to meet prespecified tolerance in the total probability density error. For any system in which a sufficiently accurate FSP exists, the FSP algorithm is shown to converge in a finite number of steps. The FSP is utilized to solve two examples taken from the field of systems biology, and comparisons are made between the FSP, the SSA, and leaping algorithms. In both examples, the FSP outperforms the SSA in terms of accuracy as well as computational efficiency. Furthermore, due to very small molecular counts in these particular examples, the FSP also performs far more effectively than leaping methods.

We study the liquid structure and solvation forces of dense monovalent electrolytes (LiCl, NaCl, CsCl, and NaI) in a nanometer slab-confinement by explicit-water molecular dynamics (MD) simulations, implicit-water Monte Carlo (MC) simulations, and modified Poisson-Boltzmann (PB) theories. In order to consistently coarse-grain and to account for specific hydration effects in the implicit methods, realistic ion-ion and ion-surface pair potentials have been derived from infinite-dilution MD simulations. The electrolyte structure calculated from MC simulations is in good agreement with the corresponding MD simulations, thereby validating the coarse-graining approach. The agreement improves if a realistic, MD-derived dielectric constant is employed, which partially corrects for (water-mediated) many-body effects. Further analysis of the ionic structure and solvation pressure demonstrates that nonlocal extensions to PB (NPB) perform well for a wide parameter range when compared to MC simulations, whereas all local extensions mostly fail. A Barker-Henderson mapping of the ions onto a charged, asymmetric, and nonadditive binary hard-sphere mixture shows that the strength of structural correlations is strongly related to the magnitude and sign of the salt-specific nonadditivity. Furthermore, a grand canonical NPB analysis shows that the Donnan effect is dominated by steric correlations, whereas solvation forces and overcharging effects are mainly governed by ion-surface interactions. However, steric corrections to solvation forces are strongly repulsive for high concentrations and low surface charges, while overcharging can also be triggered by steric interactions in strongly correlated systems. Generally, we find that ion-surface and ion-ion correlations are strongly coupled and that coarse-grained methods should include both, the latter nonlocally and nonadditive (as given by our specific ionic diameters), when studying electrolytes in highly inhomogeneous situations.

A dichloro derivative of lucigenin has been synthesized and found to exhibit almost no fluorescence. Calculations using the graphical unitary group approach (GUGA), as implemented in the GAMESS program suite and using the full Brett-Pauli spin-orbit operator yields unusually large spin-orbit coupling (SOC) values. Comparison with experimental and theoretical results for similar systems identify the intramolecular heavy-atom effect (HAE) observed for chlorine in this system to be comparable to that observed for bromosubstituted polyaromatics in earlier studies.

Aluminium, gallium and indium dihydrides have been synthesized by reaction of molecular hydrogen with excited *S and 'D metal atoms (M) isolated in solid argon. Narrow band excitations show that insertion occurs efficiently from the 'S and 'D excited states as previously reported by Pamis and Ozin for aluminium, but also takes place equally well with gallium and indium. Monohydride formation MH, + MH + H' is evidenced when the dihydrides are subsequently excited with more energetic light (4.8 to 4.3 eV). Complete sets of isotopic substitutions ( MH2, MHD and MD2) are reported for each metal for all three normal modes, and the 69Ga/7'Ga isotopic structure can be observed for gallium dihydrlde. Subsequent force field calculations demonstrate nearly identical GaH, and AlH2 bond force constants, while the InH, value is substantially smaller. These findings are indeed reflected in the bond distances which have been calculated using UHF, CCSD and DFI'methcds. However reproduction of the spectral characteristics provides a crucial test for the quality of the basis set as well as for the calculation method. Only DlT and CCSD methods are capable of reliably predicting the frequencies (less than 5% average error). 0301-0104/94/$07.00 0 1994 Elsevier Science B.V. All rights reserved SSDIO301-0104 (94)00110-V

Calculations of the molecular structure and normal vibration frequencies have been performed using ADF (Amsterdam Density Functional) program package for initial structural data of 1-aminopyridinium iodide, (1-NH 2 C 5 H 5 N) + I À , low temperature phase (110 K). Cambridge Structural Database survey has been carried out in order to explore hydrogen bond patterns of 1-aminopyridinium ring and to analyze the strength of intermolecular N-HÁ Á ÁI À interactions. Infrared spectra of powdered (1-NH 2 C 5 H 5 N) + I À in a frequency range 4000-400 cm À1 in a wide temperature region (from 300 to 413 K), covering ferroelasticparaelastic phase transition at 384/383 K (heating/cooling), are presented and analyzed. The mechanism of the phase transition is discussed. A B C Fig. 8. (a) Temperature evolution of the IR spectra in the s(NH 2 ) and c(ring) vibrations region (680-470 cm À1 ), (b) the wavenumber position of these modes between 300 and 413 K and (c) the FWHM values of the bands vs temperature.

The 351 nm photoelectron spectra of Mo Ϫ and MoO Ϫ have been measured. The electron affinity of atomic molybdenum is 0.748͑2͒ eV and that of molybdenum monoxide is 1.290͑6͒ eV. The term energies of several MoO electronic states not previously observed are obtained and compared with ab initio predictions. The ground state of MoO is confirmed to have 5 ⌸ symmetry and the term energy of the 3 ⌸ excited state, 10 179͑20͒ cm Ϫ1 , closely matches calculations. The ground state of MoO Ϫ is a 4 ⌸ state with a vibrational frequency of 810͑40͒ cm Ϫ1. The first excited state of molybdenum monoxide is tentatively assigned as a 3 ⌬ state with T 0 ϭ621(50) cm Ϫ1. At least one state, possibly a 5 ⌺ Ϫ state, lies 8000͑500͒ cm Ϫ1 above the ground state, and a 5 ⌺ ϩ state is observed at 11 590͑60͒ cm Ϫ1 above the ground state. The separations of spin-orbit levels for the MoO X 5 ⌸, 3 ⌸, and 3 ⌬ states are 169͑30͒, 410͑20͒, and Ϫ720͑20͒ cm Ϫ1 , respectively. The vibrational frequencies of the 3 ⌸ and 3 ⌬ states are found to be 600͑20͒ and 1000͑20͒ cm Ϫ1 , respectively. These observations give new insight into the MoO bond.

We report results from high-resolution studies of D 5 + cluster ion collisions with low-energy electrons performed in a heavy ion storage ring. Absolute dissociative recombination (DR) and dissociative excitation (DE) cross sections were determined for the energy range from 0.0005 to 20 eV. The DR cross sections were exceedingly large at low energies, and DR resulted in efficient internal energy redistribution and pronounced fragmentation with two main product channels: D 2 + 3D (0.62 ± 0.03) and 2D 2 + D (0.35 ± 0.01). The DR and DE cross sections were comparable in the energy range from 0.2 to 20 eV, which suggest that the two processes follow similar dynamics and are competing outcomes of the ion-electron interaction. A simple picture of the recombination process of D 5 + which captures the essential physics is suggested.

-cd 11 January 1985 . : ~. -Using common f&c basis sets we have axnpartd the'cquation of motion and the polarization prupagator method. bo:-h through second order. Calculations are perfomxed of excitation energIts and oscillator strengths for CO, and N1 and WC find thatcx~~ationcncrgicsin--a~wixhinLhtcxpcsceda caxxaq-while in somecases there k-e sub&tial dif&&es bctxvam osciuator StraIgths. D

The dynamics of molecular isomerizations that involve major charge redistributions are studied using picosecond lasers. The usual assumptions that the isomerization barrier is independent of temperature and constant within a solvent series are found to be incorrect due to solvent polarity effects. Polarity and hydrogen bonding effects on isomerizations involving large dipole moment changes Q-dimethylaminobenzoniWile) and those involving a polar intermediate (t-stilbene) are discussed.

We present a fully Hamiltonian and computationally efficient scheme to include the electrostatic effects due to the classical environment in a Car-Parrinello mixed quantum Mechanics/molecular mechanics ͑QM/MM͒ method. The polarization due to the MM atoms close to the quantum system is described by a Coulombic potential modified at short range. We show that the functional form of this potential has to be chosen carefully in order to obtain the correct interaction properties and to prevent an unphysical escape of the electronic density to the MM atoms ͑the so-called spill-out effect͒. The interaction between the QM system and the more distant MM atoms is modeled by a Hamiltonian term explicitly coupling the multipole moments of the quantum charge distribution with the classical point charges. Our approach remedies some of the well known deficiencies of current electrostatic coupling schemes in QM/MM methods, allowing molecular dynamics simulations of mixed systems within a fully consistent and energy conserving approach.

Single dye molecules at cryogenic temperatures display many spectroscopic phenomena known from free atoms and are thus promising candidates for fundamental quantum optical studies. However, the existing techniques for the detection of single molecules have either sacrificed the information on the coherence of the excited state or have been inefficient. Here we show that these problems can be addressed by focusing the excitation light near to the absorption cross section of a molecule. Our detection scheme allows us to explore resonance fluorescence over 9 orders of magnitude of excitation intensity and to separate its coherent and incoherent parts. In the strong excitation regime, we demonstrate the first observation of the Mollow triplet from a single solid-state emitter. Under weak excitation we report the detection of a single molecule with an incident power as faint as 150 attoWatt, paving the way for studying nonlinear effects with only a few photons.

The 'whispering gallery' effect has been known since ancient times for sound waves in air 1,2 , later in water and more recently for a broad range of electromagnetic waves: radio, optics, Roentgen and so on 3-6. It consists of wave localization near a curved reflecting surface and is expected for waves of various natures, for instance, for atoms 7,8 and neutrons 9. For matter waves, it would include a new feature: a massive particle would be settled in quantum states, with parameters depending on its mass. Here, we present for the first time the quantum whispering-gallery effect for cold neutrons. This phenomenon provides an example of an exactly solvable problem analogous to the 'quantum bouncer' 10 ; it is complementary to the recently discovered gravitationally bound quantum states of neutrons 11. These two phenomena provide a direct demonstration of the weak equivalence principle for a massive particle in a pure quantum state 12. Deeply bound whispering-gallery states are long-living and weakly sensitive to surface potential; highly excited states are short-living and very sensitive to the wall potential shape. Therefore, they are a promising tool for studying fundamental neutron-matter interactions 13-15 , quantum neutron optics and surface physics effects 16-18. The classical whispering-gallery phenomenon can be understood in terms of geometrical optics. Thus, neutron Garland trajectories with a high probability of specular reflection have been observed in curved neutron guides 19 and frequently used in neutron experiments. Elliptical focusing neutron guides using a single reflection are available in commerce. Sound can be reflected in an elliptical chamber from one focus to the other one after 'a single bounce'. A more complex phenomenon consists of wave localization in the vicinity of curved surfaces, also called the whispering-gallery effect. Owing to such localization, the sound can reach a person on the opposite side of a building, or even complete a circle, imitating an 'echo'. Lord Rayleigh explained and described quantitatively this phenomenon in his 'Theory of sound' 1,2. He verified the theory using a whistle as a sound source and burning candles as the sound intensity 'detectors'. Whales are believed to communicate over long distances, profiting from a similar effect in surface layers of sea water. The electromagnetic whispering-gallery waves from radio to light ('glory' or 'heiligenschein') and Roentgen frequencies are of ever-growing interest 3-6 owing to their multiple applications. They are also known as 'Mie scattering' in light scattering from aerosols and in nuclear physics. An optical analogue of a quantum particle bouncing on a hard surface under the influence of gravity or centrifugal potential has been demonstrated recently using a circularly curved optical waveguide 20. In all of these cases, a curved mirror acts as a waveguide; and interference of the waves falling to the mirror and those reflected causes specific stationary whispering-gallery modes. For a material wave in a quantum limit 7-9 , a new feature would appear: radial motion of a massive object would be settled in quantum states, with parameters depending on its mass. At

Scanning tunneling microscopy is used to study low temperature grown (LTG) InGaAs, with and without Be doping. The Be-doped material is observed to contain significantly fewer AsGa antisite defects than the undoped material, with no evidence found for Be-As complexes. Annealing of the LTG-InGaAs forms precipitates preferentially in the undoped material. The previously observed dependence of the optical response time on Be-doping and annealing is attributed to changes in the As antisite concentration and the compensation effect of the Be. Low temperature grown (LTG) III-V semiconductor materials are known to contain excess arsenic. This change in the stoichiometry leads to several interesting properties such as a fast absorption recovery time or a high resistivity when the materials are subsequently annealed. Although most of the LTG semiconductor materials studies to date have been performed on GaAs, the possibility of producing devices having a subpicosecond return to equilibrium dynamic in the 1.55 µm wavelength region has produced a growing interest in LTG-InGaAs and InGaAs/InAlAs multiquantum well structures. Compared to LTG-GaAs, the concentration of As-based deep centers is smaller in LTG-InGaAs,[3] resulting in a longer absorption recovery time in undoped material.[4] When LTG-InGaAs is doped with beryllium, the photoexcited free-carrier lifetime becomes shorter and comparable to that of LTG-GaAs (subpicosecond electron lifetimes have been observed ). Whereas annealing of undoped material is found to dramatically slow the absorption recovery time,[6] Be doping maintains the fast recovery time. To explain this effect, the presence of midgap states has been proposed, arising from complexes between Be dopants and the excess As introduced during growth. The direct compensation effect of the Be has also been suggested. In this work, we report a study of undoped and Be-doped LTG-InGaAs layers by scanning tunneling microscopy and spectroscopy. The scanning tunneling microscope (STM) has been previously used to observe defects in LTG-GaAs.[6] As for that case, we observe in LTG-InGaAs the presence of arsenic antisites. We find a significantly lower concentration of antisites in the asgrown Be-doped material compared to the undoped material (with the difference being much great-

Dissociation fraction of CO 2 molecules was measured in an early afterglow of microwave plasma by catalytic probes. The experiments were performed using the MESOX facility at the focus of the 5 kW solar furnace of PROMES-CNRS. Plasma was created in a quartz tube within a microwave cavity powered with a generator with adjustable power between 200 and 1200 W and frequency of 2450 MHz. The dissociation fraction was measured by catalytic probes at different flows of carbon dioxide gas up to 20 l h À1 corresponding to different pressures up to 150 Pa. The dissociation fraction reached 13% at the pressure of about 20 Pa. The density of O atoms at the probe position was increasing with discharge power and was almost 10 21 m À3 at the highest power. A broad maximum in the O-atom density versus pressure was observed. The results were explained by gas-phase and surface reactions.

Crystal structures of three derivatives of phenylpropionic acid, 2, 3 and 4 with hydroxyl, methyl and methoxy substitutions at the 2, 4 positions have been determined from X-ray powder diffraction data and their electronic structures were calculated at the DFT level. The optimized molecular geometries agree closely to that obtained from the crystallographic analysis. Intermolecular O-H. . .O hydrogen bonds generate R 2 2 (8) rings, which are further connected through O-H. . .O and C-H. . .O hydrogen bonds into two-dimensional framework in 2 and 4, and a step like architecture in 3. The HOMO-LUMO energy gap (>4.0 eV) indicates a high kinetic stability of the three compounds.

Precise energy eigenvalues of doubly excited 1;3 D o states originating from 2pnd ðn ¼ 3-8Þ configuration of two-electron atoms ðZ ¼ 3-7Þ have been calculated by using Ritz variational method in Hylleraas coordinates. Except for a few, the present non-relativistic energy values are the lowest yet obtained. The energy eigenvalues of a number of these states are being reported for the first time. Comparisons with existing experimental results are also made. The effective quantum numbers ðn Ã Þ for the states mentioned above have been calculated using the theory of quantum defect.

La 1Àx Ca x MnO 3 (LCMO) nanowires were prepared using a simple sol-gel process and nano-channel alumina (NCA). X-ray diffraction (XRD) and selected-area electron diffraction (SAED) indicate that the nanowires are of monoclinic perovskite structure. Transmission electron microscopy (TEM) shows that the diameters of nanowires are around 30 nm. Furthermore, high-resolution TEM reveals a clear lattice image of {0 2 1} planes in a LCMO nanowire. It can be expected that the method presented in this Letter is also appropriate for the preparation of nanowires of other monocomponent or multi-component oxides. Ó

A method was developed to chemically functionalize graphene sheets by silylation. The graphene oxide sheets were silanized with N-(trimethoxysilylpropyl) ethylenediamine triacetic acid. Then the silanized graphene oxide sheets were reduced to produce water-soluble graphene derivatives (EDTA–graphenes). Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the structures and properties of the EDTA–graphenes and to

Most lanthanide porphyrin derivatives exhibit 'normal' absorption spectra with Q and B bands. The rare earth ions have little effect on the absorption spectra, which are much like those of other closed-shell metalloporphyrins. However, their emission spectra vary according to which lanthanide ion is present. We observe two types of emissions: (i) a line emission arising from the lanthanide ion f-f transitions and (ii) p-p * emission from the triplet state of porphyrin. In this Letter, we focus on the emission from gadolinium porphyrin complexes. The oxygen sensitivity was measured in solution and polymeric film. Both intensity and lifetime Stern-Volmer plots were measured.

Analytic potentials are built for all four 2S+1Πu/g states of Li2 dissociating to Li(2S) + Li(3P): 3b(33Πu), 3B(31Πu), 3C(31Πg), and 3d(33Πg). These potentials include the effect of spin-orbit coupling for large internuclear distances, and include state of the art long-range constants. This is the first successful demonstration of fully analytic diatomic potentials that capture features that are usually considered too difficult to capture without a point-wise potential, such as multiple minima, and shelves. Vibrational energies for each potential are presented for the isotopologues 6,6Li2, 6,7Li2, 7,7Li2, and the elusive `halo nucleonic molecule' 11,11Li2. These energies are claimed to be accurate enough for new high-precision experimental setups such as the one presented in {[}Sebastian \emph{et al.} Phys. Rev. A, \textbf{90}, 033417 (2014){]} to measure and assign energy levels of these electronic states, all of which have not yet been explored in the long-range region. Measuring energies in the long-range region of these electronic states may be significant for studying the ab initio vs experiment discrepancy discussed in [Tang et al. Phys. Rev. A, 84, 052502 (2014)] for the C3 long-range constant of Lithium, which has significance for improving the SI definition of the second.