Dynamics Of Cu Research Articles

Femtosecond dynamics of Cu(CD3OD)

We report the femtosecond nuclear dynamics of Cu(CD3OD) van der Waals clusters, investigated using photodetachment-photoionization spectroscopy. Photodetachment of an electron from Cu-(CD3OD) with a 150 fs, 398 nm laser pulse produces a vibrationally excited neutral complex that undergoes ligand reorientation and dissociation. The dynamics of Cu(CD3OD) on the neutral surface is interrogated by delayed femtosecond resonant two-photon ionization. Analysis of the resulting time-dependent signals indicates that the nascent Cu(CD3OD) complex dissociates on two distinct time scales of 3 and 30 ps. To understand the origins of the observed time scales, complimentary studies were performed. These included measurement of the photoelectron spectrum of Cu-(CD3OD) as well as a series of calculations of the structure and the electronic and vibrational energies of the anion and neutral complexes. Based on the comparisons of the experimental and calculated results for Cu(CD3OD) with those obtained from earlier studies of Cu(H2O), we conclude that the 3 ps time scale reflects the energy transfer from the rotation of CD3OD in the complex to the dissociation coordinate, while the 30 ps time scale reflects the energy transfer from the excited methyl torsion states to the dissociation coordinate.

Energetics and dynamics of Cu(001)-c(2×2)Cl steps

The energetics of the step faceting transition of Cu(001) [copper (001) surface] upon Cl (chloride) adsorption in contact with HCl (hydrogen chloride) solution is modeled in terms of a solid-on-solid model that incorporates both nearest-neighbor and next-nearest-neighbor interactions. It is shown that faceting of the closed packed [110] Cu(001) steps into step segments oriented along [010] directions of the Cu(001)-c(2×2)Cl can be explained by a strongly repulsive interaction between next-nearest-neighbor Cl atoms in the c(2×2) adlayer. The dynamics of kink motion along the [010]-oriented steps of the Cl-covered Cu(001) surface via attachment/detachment is studied with scanning tunneling microscopy. At some kink sites local dissolution takes place, whereas at other kink sites growth occurs. After correcting for the net local dissolution (or growth) process the kinks perform a one-dimensional random walk along the [010] oriented step segments.

Unusual glass-like systems – relaxation dynamics of Cu + ions in ferroelectric KTN crystals

We present a broadband dielectric spectroscopy study of potassium tantalate niobate (KTN) crystals, doped with varying amounts of Cu ions. The dielectric landscape in frequency and temperature is rich, with multiple processes in different temperature phases of the crystals. Of particular interest are the processes resulting from Cu and Nb ions in the paraelectric phase of the crystal and from Cu ions in the ferroelectric phase. The linear dependence of the ferroelectric transition temperature in KTN crystals (KTa 0.62Nb 0.38O 3Cu) on the concentration of Nb, as well as the dielectric behavior of the ferroelectric phase transition in these crystals, are well known. We concentrate of the dielectric relaxation resulting from the Cu ions in the crystal lattice. Cu dopants in very small concentrations have been added in the past to enhance the photorefractive properties of KTN crystals. However the small ionic radius of such dopants, relative to their lattice site, results in virtual dipoles exhibiting dielectric relaxation. The random nature of their distribution throughout the ordered KTN lattice leads to relaxation behavior reminiscent of glass formers. In particular Vogel Fulcher Tammann relaxation of these ions is evident in the paraelectric phase of the crystal. This cooperativity is broken at a critical temperature ( T = 354 K) and the relaxation becomes Arrhenius in nature. An explanation in terms of Adam–Gibbs theory is presented where the cooperative cluster is realized by polarized Nb ions linking the widely space Cu ions. At the phase transition ( T c = 295.6 K) this relaxation is ‘frozen’ by large internal fields caused by the structural shift of the Nb ion in the unit cell. As the temperature drops the Cu ions undergo a reorganization about the multiwell potential leading to a saddle-like process characteristic of liquids in confined systems. An explanation for this behavior is proposed based on free volume concepts, where the relatively small ionic radius of the Cu ions provides the free volume for the relaxing species. The role of the oxygen octahedra as the relaxing species is discussed.

Femtosecond dynamics of Cu(H2O)2

The ultrafast relaxation dynamics of Cu(H(2)O)(2) is investigated using femtosecond photodetachment-photoionization spectroscopy. In addition, stationary points on the Cu(H(2)O)(2) anion, neutral, and cation potential energy surfaces are characterized by ab initio electronic structure calculations. Electron photodetachment from Cu(-)(H(2)O)(2) initiates the dynamics on the ground-state potential energy surface of neutral Cu(H(2)O)(2). The resulting Cu(H(2)O)(2) complexes experience large-amplitude H(2)O reorientation and dissociation. The time evolution of the Cu(H(2)O)(2) fragmentation products is monitored by time-resolved resonant multiphoton ionization. The parent ion, Cu(+)(H(2)O)(2), is not detected above background levels. The rise to a maximum of the Cu(+) signal from Cu(-)(H(2)O)(2), and the decay of the Cu(+)(H(2)O) signal from Cu(-)(H(2)O)(2) have similar tau approximately 10 ps time dependences to the corresponding signals from Cu(-)(H(2)O), but display clear differences at very short and long times. The experimental observations can be understood in terms of the following picture. Prompt dissociation of H(2)O from nascent Cu(H(2)O)(2) gives rise to a vibrationally excited Cu(H(2)O) complex, which dissociates to Cu+H(2)O due to coupling of H(2)O internal rotation to the dissociation coordinate. This prompt dissociation removes all intra-H(2)O vibrational excitation from the intermediate Cu(H(2)O) fragment, which quenches the long time vibrational predissociation to Cu+H(2)O previously observed in analogous experiments on Cu(-)(H(2)O).

Conformational dynamics of Cu(i) complexes of tripodal ligands: steric control of molecular motion

The dynamics of molecular conformational changes for Cu(I) complexes of two tripodal ligands were studied. Variable-temperature NMR and circular dichroism in combination with two-dimensional NMR experiments were employed to determine the structural and energetic details of a dynamic process in which one of three arms dissociates from coordination to Cu(I). Dissociation was triggered by addition of a strongly coordinating anion (SCN−). One-electron oxidation to the Cu(II) complex returned coordination of all three ligand arms. The observed phenomena were dependent upon steric crowding; addition of a single methyl group to one arm resulted in marked differences in behavior. The CuSCN and CuPF6 complexes of tris(2-quinolylmethyl)amine (TQA) and the CuPF6 complex of 1-(quinolin-2-yl)-N,N-bis(quinolin-2-ylmethyl)ethanamine (MeTQA) did not give any evidence for differences in coordination over the temperature range 0–35 °C, while CuI(MeTQA)NCS demonstrated marked differences in NMR but not CD spectra over this temperature range. In the latter complex, two diastereotopic arms displace each other with a transition energy of 14.0 kcal mol−1. The structure of the arm-dissociated complex contains a higher degree of stereochemical complexity than the tetradentate complexes.

Photoluminescence properties of impurity-doped ZnS nanocrystals fabricated by sequential ion implantation

We have studied photoluminescence (PL) spectrum and dynamics of Cu- and Al-doped ZnS (ZnS:Cu,Al) nanocrystals fabricated by sequential implantation of Zn +, S +, Cu +, and Al + ions into Al 2O 3 matrices. These samples exhibit intense green PL under UV light excitation. The space- and time-resolved PL measurements show that the broad green PL is due to the donor–acceptor (DA) pair luminescence of single ZnS:Cu,Al nanocrystals.

Femtosecond study of Cu(H2O) dynamics

The short-time nuclear dynamics of Cu(H(2)O) is investigated using femtosecond photodetachment-photoionization spectroscopy and time-dependent quantum wave packet calculations. The Cu(H(2)O) dynamics is initiated in the electronic ground state of the complex by electron photodetachment from the Cu(-)(H(2)O) complex, where hydrogen atoms are oriented toward Cu. Several time-resolved resonant multiphoton ionization schemes are used to probe the ensuing reorientation and dissociation. Immediately following photodetachment, the neutral complex is far from its minimum energy geometry and possesses an internal energy comparable to the Cu-H(2)O dissociation energy and undergoes both large-amplitude H(2)O motion and dissociation. Dissociation is observed to occur on three distinct time scales: 0.6, 8, and 100 ps. These results are compared to the results of time-dependent J=0 wave packet calculations, propagating the initial anion vibrational wave functions on the ground-state potential of the neutral complex. An excellent agreement is obtained between the experimental results and the ionization signals derived from the calculated probability amplitudes. Related experiments and calculations are carried out on the Cu(D(2)O) complex, with results very similar to those of Cu(H(2)O).

Time resolved solvent rearrangement dynamics.

Ultrafast pump-probe studies of I2- recombination in size-selected I2- (CO2)n cluster ions demonstrate long time coherent motions in size-selected clusters and the resulting non-statistical energy flow in the cluster. For I2- photodissociated to produce either I- + I or I- + I*, we identify a solvent-driven energy transfer process without a condensed phase counterpart. The mechanism involved is a Marcus-like solvent-driven curve crossing, with the driving force arising from asymmetric solvation, not just from solvent orientation. By substituting another halogen for one I atom, we "break" the I2- symmetry, and thus obtain direct information on the electron transfer process. New experiments on IBr- (CO2)n photodissociation products confirm the behavior suspected in the I2- studies. Time-resolved experiments on IBr- and theoretical modeling of the dynamics provide quantitative information on the multiple curve crossings encountered in the recombination process. In related investigations, femtosecond negative ion-neutral-positive ion charge reversal apparatus is employed to investigate transient neutral species evolving along a reaction coordinate. We report studies of the rearrangement dynamics of Cu(OH2) produced by photodetachment of the corresponding anion. Following a controlled delay period, a second ultrafast tunable laser pulse initiates resonant multiphoton photoionization of the time-evolving Cu...OH2 complex. The time-resolved Cu+ and Cu+(OH2) signals provide information both on the prompt dissociation of the complex and on energy redistribution between internal rotational and radial modes of the evolving complex. Calculations of the time evolution of the anion geometric configuration on the neutral potential energy surface yield deeper insight into the nature of the rearrangement process and the energy flow within the complex.

Effects of Poly‐ and Orthophosphates on the Dynamics of Manganese, Zinc, and Copper in Plant and Soil Material of Varied pH

A laboratory experiment was performed on light loamy sand to study the effect of potassium polyphosphate [(KPO3)n], potassium dihydrogen phosphate (KH2PO4) and triple superphosphate + potassium chloride (KCl) on the content and dynamics of soil manganese (Mn), zinc (Zn), and copper (Cu) determined using the methods of Rinkis (R) and Egner‐Riehm‐Domingo (AL) depending on the form and rate of PK fertilizers, different soil pH and Mn + Zn + Cu (M) supplementation. The results obtained by Rinkis's method were used to describe the dynamics of the three microelements. The average Mn, Zn, and Cu content in soil (determined in 1 mol dm− 3 HCl solution) was to a small extent related to the form and dose of PK fertilization. Increasing rates of CaCO3 caused an increase in the average Mn content in soil, an increase in Cu content only in soil of pH 7.49, but a decrease in Zn. The average Mn content in soil increased to day 40 of the experiment. The analyzed forms of Zn and Cu were retarded until day 20 of the experiment, after which they were activated in the course of time. The form of the fertilizer applied had a significant influence on the dynamics of Mn, a slight effect on the dynamics of Zn and, in general, had no influence on the dynamics of Cu. The most considerable retardation of Mn and Cu was observed in the objects fertilized with KH2PO4. The effect of increased (KPO3)n and KH2PO4 rates on the content of Mn, Zn, and Cu in soil was ambiguous and related to the soil pH and Mn + Zn + Cu supplementation. Soil higher doses of superphosphate + KCl resulted in a lower content of Mn2 +. It was only in soil of pH 7.08 that Mn + Zn + Cu supplementation caused an increase in the concentration of the analyzed forms of the microelements. In soil of other pH the effect of this supplementation was ambiguous. The correlation between soil pH and the soil content of the analyzed microelements was significantly positive for Mn, negative for Zn, and non‐significant for Cu. In a vegetative trial, soil fertilization with KH2PO4 and (KPO3)n without M supplementation increased the average total biomass yield of barley, compared to the effect achieved by triple superphosphate + KCl fertilization. Soil liming depressed the average total yield of the crop. The M supplementation decreased the total greenmass of barley grown only on soil limed to pH 5.88 in all the fertilization objects. Compared to the objects with triple superphosphate + KCl, application of (KPO3)n and KH2PO4 decreased the content and uptake of Mn by barley in all the objects, those of Zn, only in non‐limed soil, and had no effect on Cu. Liming decreased the content and uptake of Mn by barley more than the content and uptake of Zn. The Cu content and uptake by barley was related to the Mn + Zn + Cu supplementation rather that the PK fertilizer form or soil reaction. Correlation between the content of the microelements in soil and in plants in the analogous time of the study was negative for Mn, positive for Zn in the second and third cut, and for Cu in the first and second cut.

Soil solution dynamics of Cu and Zn in a Cu- and Zn-polluted soil as influenced by γ-irradiation and Cu–Zn interaction

A pot experiment was conducted to study soil solution dynamics of Cu and Zn in a Cu/Zn-polluted soil as influenced by γ-irradiation and Cu–Zn interaction. A slightly acid sandy loam was amended with Cu and Zn (as nitrates) either singly or in combination (100 mg Cu and 150 mg Zn kg −1 soil) and was then γ-irradiated (10 kGy). Unamended and unirradiated controls were included, and spring barley ( Hordeum vulgare L. cv. Forrester) was grown for 50 days. Soil solution samples obtained using soil moisture samplers immediately before transplantation and every ten days thereafter were used directly for determination of Cu, Zn, pH and absorbance at 360 nm (A 360). Cu and Zn concentrations in the solution of metal-polluted soil changed with time and were affected by γ-irradiation and metal interaction. γ-Irradiation raised soil solution Cu substantially but generally decreased soil solution Zn. These trends were consistent with increased dissolved organic matter (A 360) and solution pH after γ-irradiation. Combined addition of Cu and Zn usually gave higher soil solution concentrations of Cu or Zn compared with single addition of Cu or Zn in γ-irradiated and non-irradiated soils, indicating an interaction between Cu and Zn. Cu would have been organically complexed and consequently maintained a relatively high concentration in the soil solution under higher pH conditions. Zn tends to occur mainly as free ion forms in the soil solution and is therefore sensitive to changes in pH. The extent to which γ-irradiation and metal interaction affected solubility and bioavailability of Cu and Zn was a function of time during plant growth. Studies on soil solution metal dynamics provide very useful information for understanding metal mobility and bioavailability.

Low-energy spin dynamics of CuO chains in YBa 2Cu 3O 6+ x

We study the spin fluctuation dynamics of Cu–O chains in the oxygen deficient planes of YBa 2Cu 3O 6+ x . The chains are described by a model including antiferromagnetic interactions between the spins and Kondo-like scattering of the oxygen holes by the copper spins. There are incommensurate spin fluctuations along the direction of the chains. The dynamic structure factor of this system is qualitatively different from that of a quasi one-dimensional localized antiferromagnet due to the presence of itinerant holes. We compute the dynamic structure factor that could be measured in neutron scattering experiments.

The structure and dynamics in solution of Cu(I) pseudoazurin from Paracoccus pantotrophus.

The solution structure and backbone dynamics of Cu(I) pseudoazurin, a 123 amino acid electron transfer protein from Paracoccus pantotrophus, have been determined using NMR methods. The structure was calculated to high precision, with a backbone RMS deviation for secondary structure elements of 0.35+/-0.06 A, using 1,498 distance and 55 torsion angle constraints. The protein has a double-wound Greek-key fold with two alpha-helices toward its C-terminus, similar to that of its oxidized counterpart determined by X-ray crystallography. Comparison of the Cu(I) solution structure with the X-ray structure of the Cu(II) protein shows only small differences in the positions of some of the secondary structure elements. Order parameters S2, measured for amide nitrogens, indicate that the backbone of the protein is rigid on the picosecond to nanosecond timescale.

Oxidative Chloride Adsorption and Lead Upd on Cu(100): Investigations into Surfactant-Assisted Epitaxial Growth

The influence of chloride adsorption and lead upd on the step dynamics of Cu(100) has been examined in acid perchlorate solution. A c(2 × 2) Cl adlayer is formed upon immersion of a Cu(100) electrode leading to step faceting in the 〈100〉 direction. At more negative potentials an order−disorder transformation occurs leading to significant rearrangement of the steps. Alternatively, in an electrolyte containing Pb2+ the halide adlayer may be completely displaced by lead upd. Images of orthogonal surface steps in combination with an assessment of the coulometry suggest that the lead adlayer forms either a highly defective c(2 × 2), c(5√2 × √2)R45° or a disordered structure corresponding to a coverage ranging from 0.5 to 0.6. The transformation from the halide to the lead adlayer results in the formation of vacancies and adatoms which condense to form holes and islands, respectively. These features may be rationalized by the formation of an alloy phase at low coverage, which subsequently dealloys as the coverage approaches 0.5. The extent of the morphological changes associated with the alloying/dealloying processes is strongly path dependent. Voltammetry reveals that the stripping of the lead upd layer is associated with two oxidation waves. As the potential is increased beyond the peak of the first wave islands disappear which may be due to alloy formation occurring coincident with partial desorption of the lead. The second wave is associated with the nucleation 〈100〉-oriented rows of the c(2 × 2) Cl adlayer which propagate across the terraces displacing the lead phase. The use of metal upd and anions as surfactants in the electrochemical deposition of copper is likely to prove even more interesting than in vacuum deposition since the surfactant coverage and its effect on mesoscopic structure can be continuously manipulated by potential control.

STM investigation of step orientation and surface dynamics of Cu(111) in hydrochloric acid electrolyte

× )R30° structure of the adsorbate. The surface structure and dynamics, such as step orientation, step dynamics, and the stability of small copper piles, are markedly influenced by the adsorbed species. The reordering of steps along the close-packed Cl rows and the decomposition of a pile of terraces were observed using atomic resolution scanning tunneling microscopy (STM).

The essential dynamics of Cu, Zn superoxide dismutase: suggestion of intersubunit communication

A 300-ps molecular dynamics simulation of the whole Cu, Zn superoxide dismutase dimer has been carried out in water, and the trajectory has been analyzed by the essential dynamics method. The results indicate that the motion is defined by few preferred directions identified by the first four to six eigenvectors and that the motion of the two monomers at each instant is not symmetrical. The vectors symmetrical to the eigenvectors are significantly sampled, suggesting that, on average, the motions of the two subunits will exchange. Large intra- and intersubunit motions involving different subdomains of the protein are observed. A mechanical coupling between the two subunits is also suggested, because displacements of the loops surrounding the active site in one monomer are correlated with the motion of parts of the second toward the intersubunit interface.

Dynamics of photoexcited electrons in metals studied with time-resolved two-photon photoemission

Femtosecond time-resolved two-photon photoemission (2PPE) is used to investigate the hot electron dynamics of Cu(111), Ag(110) and Ta(poly). The experimentally derived relaxation rates of photoexcited electrons scale with the available phase space for scattering with electrons below the Fermi level and are compared with predictions from Fermi liquid theory. A simulation employing rate equations to account for hot electron lifetimes, transport effects and the creation of secondary electrons demonstrates that the relaxation dynamics is strongly influenced by secondary electron cascades. With Ag(110) a pronounced temperature dependence of the photoemission yield is observed, indicating the importance of electron-phonon scattering for momentum conservation in the 2PPE process.

35Cl NQR and 195Pt NMR spin-lattice relaxations in Zn 1−xCu xPtCl 6·6H 2O

35Cl NQR spin-lattice relaxation time T 1 Q and 195Pt NMR spin-lattice relaxation time T 1 of Zn 1− x Cu x PtCl 6·6H 2O were determined in the temperature ranges 2.1–299K and 77–400K, respectively, to study the contribution of doped paramagnetic Cu 2+ ions to the relaxation of the resonant nuclei. For comparison, 35Cl T 1 Q of ZnPtCl 6·6H 2O and CuPtCl 6·6H 2O, and 195Pt T 1 of CuPtCl 6·6H 2O were also measured in the temperature ranges 18–400K and 4.2–400K, and 77–400K, respectively. As for Zn 1− x Cu x PtCl 6·6H 2O, the magnetization recoveries of the 35Cl nucleus at low temperature and 195Pt at observed temperatures followed the exp [−( τ T 1Q ) 1 2 ] or exp [−( τ T 1 ) 1 2 ] laws respectively as a function of time τ. These results suggest that nuclear relaxation is caused by direct dipolar interaction between the resonant nuclei and doped Cu 2+ ions. From T 1 Q and T 1, the electron spin correlation time of Cu 2+ was estimated. The electron spin dynamics of Cu 2+ can be explained by the transition between the three distorted configurations, a result of the Jahn-Teller effect, and even at low temperature the transition can be considered to occur quite frequently. To confirm this fast transition, Cu 2+ ESR spectra of single crystals of Zn 1− x Cu x PtCl 6·6H 2O were measured.

Monovalent copper-activated oxygenated insulators

Abstract The photoluminescence of monovalent copper in oxygenated insulators has been extensively studied. The spectroscopy and the excited states dynamics of Cu+ ions were investigated as a function of the copper concentration and temperature in various glassy and crystallized materials, essentially borates and phosphates. The broad band fluorescences observed in the visible range under UV excitation arise from two main emitting centers: isolated Cu+ ions and (Cu+)2 pairs. The spectroscopic characteristics of isolated Cu+ depend strongly on the local structure, whereas those of the copper pairs remain nearly unaltered whatever the host-matrix. Energy diagrams are proposed for both centers, using ab initio LCAO calculations, in connection with structural investigations involving XRD, ND and EXAFS spectroscopies. Borate glasses can be considered as potential laser sources for tunable output in the whole visible range.

Dynamics of Cu Surfaces at High Temperatures

AbstractThe structure and dynamics of Cu(100), Cu(110) and Cu(111) have been studied by Molecular Dynamics simulations using the potential derived from effective medium theory. The formation energy for adatoms is lower for Cu(llO) than for Cu(lO0) or Cu(lll). The relatively high concentration of defects on Cu(11O) makes this surface premelt near the bulk melting point. The surface diffusivity is high for all three surfaces at elevated temperatures, the diffusion mechanism at the disordered surfaces appears to be quite complicated.

Fluorescence properties of Cu + ion in phosphate glasses of the BaLiPO 4P 2O 5 system

The spectroscopy and the excited state dynamics of Cu + ion in phosphate glasses are investigated as a function of the copper concentration and temperature. The blue fluorescence is assigned to single Cu + impurity ions occupying various sites. An additional red fluorescence, not detected in weakly Cu-doped samples but which grows with copper concentration, is well interpreted in terms of (Cu +) 2 pair centers.