MRCI studies on ground and excited states of CBr

Potential curves and spectroscopic constants for a large number of doublet and quartet states of CBr were obtained by multireference configuration interaction calculations, using valence triple-zeta basis sets with polarization and diffuse functions. Besides the X²Π ground state, 1⁴Σ^?, 1²Δ and 2²Σ⁺ have been found to be stable. Spectroscopic constants calculated for 1²Δ are in excellent agreement with experimental values obtained by Dixon and Kroto in 1963. Their observed predissociation of one component of 1²Δ can be explained by the crossing of the 1²Δ potential near equilibrium by 1²Σ⁺. The 1²Σ⁺ state is calculated to have a shallow long-range minimum at 2.31?Å. The dissociation energy of X²Π is calculated to be 3.43?eV. An observed T _e of 4.97?eV for 2²Σ⁺ agrees with the theoretical value. Several Rydberg states of the 2π→Ryd and 3σ→Ryd series, starting at T _e ?=?5.25?eV, were identified. Photodissociation of CBr by sunlight, important in the ozone cycle, can occur via direct dissociation of the ground state, or by excitation to 1²Δ followed by predissociation. Most dissocative repulsive states lie at higher energies, and are not expected to participate in the photodisscociation of CBr.     

Studies on Cu(II), Zn(II), Ni(II) and Co(II) complexes derived from two dipeptide Schiff Bases

Some new metal complexes of two dipeptide Schiff bases derived from salicylaldehyde and dipeptides such as glycyl-DL-alanine and glycyl-DL-phenylalanine have been synthesized and characterized by elemental analysis, molar conductance, IR, UV spectra, TG and DTA studies. The COO stretching bands in IR spectra suggest that the carboxylate acts as a monodentate group when binding with metal. The ligands are coordinated to the central metal as tetradentate ligands. The bonding sites are the carboxylate oxygen, imino nitrogen, amide nitrogen and phenolic oxygen.     

Theoretical study of the electronic ground states and low-lying singlet excited states of thiophene-based spirofluorenes

The electronic structures and optical properties of oligothiophene substituted spirofluorenes are investigated theoretically with semi-empirical quantum chemical calculations. A theoretical investigation of the interaction between two perpendicular π-systems of various oligothiophene substituted spirofluorenes is conducted. The results demonstrate that the interaction between two perpendicular branches is reduced by oligothiophene substitutions. Photoexcitation induced relaxation is mainly located on one of...     

Phenoxide bridged tetranuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes: Syntheses,characterization and fluorescence studies

A tetranucleating compartmental Schiff base ligand system has been derived from 2,6-diformyl-4-methylphenol, p-phenylenediamine and 2-aminomethylbenzimidazole. Phenoxide bridged later first row transition metal(II) complexes of this ligand have been prepared by conventional sequential route. Ligand and complexes were characterized by routine physicochemical characterizations. The mutual influence of metal centers in terms of cooperative effect on the electronic, magnetic, electrochemical and structural properties was investigated. The Schiff-bases exhibit fluorescence originating from intraligand (π→π?) transitions. Metal mediated fluorescence enhancement is observed on complexation with Zn(II), whereas metal mediated fluorescence quenching occurs in all other complexes.     

Theoretical characterization of the ground and optically excited states of alpha'-NaV2O5

The character of the ground and optically excited states was investigated by quantum chemical calculations. We propose a rung ground state with V 3d(1)(xy)-O 2p(1)(y)-V 3d(1)(xy) character, instead of the conventional picture of one unpaired electron shared by 2 V ions. The unpaired electron on O is low-spin coupled to the V d electrons and spin density is predicted to be localized on vanadium. The absorption peak at 0.9 eV is assigned to a state with similar orbital occupations but a different spin coupling scheme, resulting in spin density localized on the bridging oxygen.     

Population densities of He(I) and He(II) excited states in plasmas

Reduced population coefficients for He(I) and He(II) levels, both for optically thin and partially optically thick conditions, have been calculated from a collisional-radiative model using recent experimental and theoretical cross sections. The calculated population densities are compared with experimental results on helium plasmas. Agreement with experimental results is better at low electron temperatures.     

Liquid ground state, gap, and excited states of a strongly correlated spin chain

We present an exact solution of an experimentally realizable and strongly interacting one-dimensional spin system which is a limiting case of a quantum Ising model with long range interaction in a transverse and longitudinal field. Pronounced quantum fluctuations lead to a strongly correlated liquid ground state. For open boundary conditions the ground state manifold consists of four degenerate sectors whose quantum numbers are determined by the orientation of the edge spins. Explicit expressions for the entanglement properties, the exact excitation gap, as well as the exact wave functions for a couple of excited states are analytically derived and discussed. We outline how this system can be experimentally realized in a lattice gas of Rydberg atoms.     

Calculation of the wave functions of the ground and weakly excited states of helium II

The wave functions of the ground (Ψ₀) and the first excited (Ψ_k) states of He II in the second-order approximation, i.e., up to the first two corrections to the corresponding solutions for a weakly nonideal Bose gas, are determined by the collective variable method, which was proposed by Bogolyubov and Zubarev and developed in the studies by Yukhnovskii and Vakarchuk. The functions Ψ₀ and Ψ_k = ψ_kΨ₀ are determined as the eigenfunctions of the N-particle Schrödinger equation from a system of coupled equations for Ψ₀, Ψ_k, and the quasiparticle spectrum E(k) of helium II. The results consist in the following: (1) these equations are solved numerically for a higher order approximation compared with those investigated earlier (the first-order approximation), and (2) Ψ₀ and ψ_k are derived from a model potential of interaction between He⁴ atoms (rather than from the structure factor as earlier) in which the potential barrier is joined with the attractive potential found from experiment. The height V ₀ of the potential barrier is a free parameter. Except for V ₀, the model does not have any free parameters or functions. The calculated values of the structure factor, the ground-state energy E ₀, and the quasiparticle spectrum E(k) of He II are in agreement with the experimental values for V ₀ ≈ 100 K. The second-order correction to the logarithm of Ψ₀ significantly affects the value of E ₀ and provides the asymptotics E(k → 0) = ck, while the second-order correction to ψ_k slightly affects the E(k). The second-order corrections to Ψ₀ and ψ_k have a smaller effect on the results compared with the first-order corrections, whereby the theory is in agreement with experiment; therefore, one may assume that the truncated Ψ₀ and ψ_k well describe the microstructure of He II. Thus, the series for Ψ₀ and Ψ_k can be truncated in spite of the fact that the expansion parameter is not very small (～1/2).     

Zeeman splitting of ground and excited acceptor states in ZnTe

Zeeman splittings of Li-acceptor states in ZnTe are investigated by Selective Pair Luminescence. From a detailed study of the polarization dependent absorption and emission of photons by donor-acceptor pairs, the g-values of both ground and excited Li-acceptor states are determined. The method presented here is appropriate to the study of donors as well as acceptors in semiconductors.     

Adsorption and thermodynamic studies of Cu(II) and Zn(II) on organofunctionalized-kaolinite

Kaolinite-bearing clay samples from Perus, São Paulo state, Brazil, were used for chemical modification process with dimethyl sulfoxide and organofunctionalized with the silyating agent (RO)₃Si(CH₂)₃NH(CH₂)₂NH₂ in the present study. The resulting material and natural kaolinite were subjected adsorpion process with Cu(II) and Zn(II) from aqueous solution at pH 6.0 and controlated temperature of 298 K. The Langmuir adsorption isotherm model has been applied to fit the experimental data. The results showed that the chemical modification process increases the basal spacing of the natural kaolinite from 0.711 to 0.955 nm. The energetic effects caused by Cu(II) and Zn(II) interactions were determined through calorimetric titration at the solid–liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant.     

Synthesis, thermal and optical properties of metal(II) complexes with a novel ligand derived from pyrazolone-5

Three novel metal(II) complexes, CoL₂, NiL₂ and CuL₂ (L = (Z)-4-(2-(1,3-dimethyl-5-oxo-1H-pyrazol-4(5H)-ylidene)hydrazinyl)-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one were synthesized. Their structures were postulated based on elemental analyses, ¹H NMR, ESI-MS, FT-IR spectra and UV-vis spectra. The effect of different central metal(II) ions on absorption bands of the metal(II) complexes in CHCl₃ solutions was researched. The result indicates that the bathochromic shift is CuL₂ > NiL₂ > CoL₂. The absorption properties of thin films and thermal stability of these complexes are also discussed. In addition, the optical constants (complex refractive index N=n+ik) and thickness of the complex thin films on polished single-crystal silicon substrates were measured by spectroscopic ellipsometry. Results indicate that the metal(II) complexes would be a promising recording medium candidate for blu-ray recordable optical storage system due to good absorption at 405 nm, high thermal stability and sharp thermal decomposition, and a high n values of 1.35–1.45 and a low k values of 0.33–0.39.     

Positronium formation cross-sections in the ground and excited states ( levels) in an -He atom collision

The positronium formation cross-sections in the ground and excited n=2 levels have been studied in an -He atom collision in the framework of eikonal approximation. Both the differential and total formation cross-sections have been investigated in the intermediate- and high-energy regime. Present eikonal results are found to differ appreciably from the corresponding first Born values even at very high incident energies. The total cross-section results have been compared with available experiments due to different groups as well as with other existing theoretical results. Received: 20 July 1998 / Received in final form: 5 January 1999     

Two-proton radioactivity of ground and excited states within a unified fission model

A unified fission model is extended to study two-proton radioactivity of the ground states of nuclei, and a good agreement between the experimental and calculated half-lives is found. The two-proton radioactivity half-lives of the ground states of some probable candidates are predicted within this model by inputting the released energies taken from the AME2020 table. It is shown that the predictive accuracy of the half-lives is comparable to those of other models. Then, two-proton radioactivity of the excited states of ¹⁴O, ^17,18Ne, ²²Mg, ²⁹S, and ⁹⁴Ag is discussed within the unified fission model and two analytical formulas. It is found that the experimental half-lives of the excited states are reproduced better within the unified fission model. Furthermore, the two formulas are not suitable for the study of two-proton radioactivity of excited states because their physical appearance deviates from the mechanism of quantum tunneling, and the parameters involved are obtained without including experimental data from the excited states.     

Alpha-particle decays from excited states in ~(24)Mg

Using a cluster model based on the Woods-Saxon potential, alpha-particle decays from excited states in 24Mg have been system atically investigated. Calculations can in general reproduce experimental data, noticing the fact that the preformation factor P of alpha particle in alpha-decaying nuclei is of order from 100 to 10?2. This can be the evidence for the α+20Ne structure in 24Mg. Meanwhile, the results also show the existence of other configurations, such as 16O+2α. Since the calculated decay widths are ...     

Mean lifetimes of excited levels of Ar(II)—II. Theoretical considerations

The experimental lifetimes given in Part I⁽¹⁾ are compared with theoretical lifetimes. Two sets of theoretical calculations obtained in intermediate coupling are considered.