Spectral distribution methods in effective interaction theory

Spectral distribution methods are used to suggest alternative forms for effective interaction calculation. Using the configuration centroid operator as the unperturbed Hamiltonian is found to yield a residual interaction with minimal Euclidean norm. If the effective interaction is expanded in terms of orthogonal polynomials appropriate to the configuration density, the leading term is more meaningful than those in existing series. Using the same technique of orthogonal polynomial expansion, the calculation of diagonal matrix elements of higher order terms in the perturbation expansions reduces to an evaluation of traces which are more easily calculable. Convergence of both polynomial expansions is tied to the convergence of the spectral density to normal form which itself is governed by a strong principle, the central limit theorem.     

Electronic structure of GaSbAlSb superlattices

We present optical absorption experiments performed at low temperature in very high quality GaSbAlSb superlattices grown by MBE. The absorption spectra exhibit pronounced exciton peaks separated by absorption plateaus. The data are interpreted within an effective mass theory, taking into account the effect of strains induced by the 0.65 % lattice mismatch of the hosts. From the number of observed transitions, we can determine quite accurately the band offsets in this system. The crossover of the quantized states originating from the Λ and L minima of the GaSb conduction band is also discussed.     

Electrode Kinetics of Lead in N-(3-Aminopropyl)-Diethanolamine Solution at the Dropping Mercury Electrode

The lead complex of N-(3-Aminopropyl)-Diethanolamine (APDEA) was investigated polarographically over the pH range 10.40-12-85 and ligand concentration 0.0227-1.002M. A quasi-reversible and diffusion-controlled reduction wave was obtained at pH≥10.40. The electron-transfer coefficient and rate constants were determined as 0.11-0.34 and 10^?4 cmsec^?1, respectively.     

τ Dependence of the vibrational zeropoint energy in the partially deuterated methyl alcohols,revisited

The contributions of the zeropoint energy from the 3N ? 7 other vibrations to the effective potential energy for internal rotation have been calculated for eight isotopic species of methyl alcohol. The basis of the calculation is the set of force constants determined by A. Serrallach, R. Meyer, and Hs. H. Günthard [J. Mol. Spectrosc.52, 94–129 (1974)] from infrared analyses. The results calculated for CH₂DOH are V₁ = 11.93 cm^?1 and V₂ = 0.17 cm^?1 with ΔV₃ < 0.05 cm^?1. These values agree favorably with the experimental results as previously determined from analysis of the microwave torsional-rotational spectra of CH₂DOH.     

Energy dependence of the optical model parameters for 3He ions scattered from 40Ca and 58Ni

The differential cross sections for the elastic scattering of ³He ions on targets of ⁴⁰Ca and ⁵⁸Ni have been measured at incident energies of 27.7, 51.4, 73.2 and 83.5 MeV. The results of optical model analyses showed that only one unique potential (J_R ≈ 330 MeV · fm³) with a surface absorptive term can provide acceptable fits to the large angle elastic scattering cross sections at 83.5 MeV. The particular geometrical set found at 83.5 MeV could not, however, give an adequate fit to the data with energy less than 40 MeV. Subsequent analyses indicated that a break in the energy dependence of the real potential is observed for the low energy data. Explicit energy dependent terms were obtained by fitting all the data simultaneously. These phenomenological potentials were also compared with the folded nucleon-nucleus potential. The influence of the α-particle channels on the elastic scattering of ³He ions at 83.5 MeV was also examined.     

An exact one-particle-irreducible renormalization-group generator for critical phenomena

An exact one-particle-irreducible renormalization-group generator for critical phenomena is derived by an infinitesimal saddle-point expansion. This replaces the usual field-theoretic loop-expansion for the free energy and Green's functions with an explicit differential equation.     

Temperature dependence of protein backbone motion from carbonyl 13C and amide 15N NMR relaxation

The NMR spin-lattice relaxation rate (R1) and the rotating-frame spin-lattice relaxation rate (R1rho) of amide 15N and carbonyl 13C (13C') of the uniformly 13C- and 15N-labeled ubiquitin were measured at different temperatures and field strengths to investigate the temperature dependence of overall rotational diffusion and local backbone motion. Correlation between the order parameter of the N-H vector, SNH2, and that of the carbonyl carbon, S2C', was investigated. The effective S2C' was estimated from the direct fit of the experimental relaxation rates and from the slope of 2R2-R1 vs. B2 using Lipari-Szabo formalism. The average SNH2 decreased by 5.9%, while the average S2C' decreased by 4.6% from 15 to 47 degrees C. At the extreme low and high temperatures the difference in the temperature dependence of the order parameters vanishes. At the intermediate temperatures they do not change by the same amount but they follow the same trend. On the same peptide plane along the protein sequence, S2C' and SNH2 are highly correlated. The results suggest that fast local motion experienced at the site of the N-H vector and carbonyl nucleus is more complicated than previously thought and it cannot be easily described by one single type of motion in a broad range of temperature.     

2,6-Bis[4-(p-dihexylaminostyryl)styryl]anthracene derivatives with large two-photon cross sections

[Structure: see text] Anthracene derivatives with a variety of donor-acceptor substituents have been synthesized and shown to exhibit large two-photon cross sections over a wide range of wavelengths.     

New insight into the solid electrolyte interphase with use of a focused ion beam

The formation and evolution of the solid electrolyte interphase (SEI) film on the surface of natural graphite spheres in the electrolyte of 1 M LiPF6 in ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio 1:1) were investigated with use of focused ion beam (FIB) technology. Secondary electron FIB images clearly show the surface and cross-section morphology of the SEI film. The composition variation along the surface and cross section of the SEI film was also explored by the elemental line scan analysis (ELSA). The initial SEI film with an apparent thickness range of approximately 450 to approximately 980 nm is rough in morphology and nonuniform in composition, and contains small splits. After certain electrochemical cycles, the thickened SEI film displays microscale holes and obvious cracks on the surface, and the content of organic compounds increases. In addition, the concept of "internal SEI film" is first proposed based on the characterization of the cross section of the natural graphite spheres with the aid of FIB. Finally, the capacity fading mechanisms of the natural graphite spheres corresponding to different electrochemical stages are discussed.     

Adsorption and reactions of ClCH2CH2OH on clean and oxygen-precovered Cu(100): experimental and computational studies

Temperature-programmed reaction/desorption, reflection-absorption infrared spectroscopy, and density functional theory calculations have been employed to investigate the adsorption and thermal reactions of ClCH2CH2OH on clean and oxygen-precovered Cu(100) surfaces. On Cu(100), ClCH2CH2OH is mainly adsorbed reversibly. The ClCH2CH2OH molecules at a submonolayer coverage can change their orientation with increasing temperature. However, on oxygen-precovered Cu(100), all of the adsorbed ClCH2CH2OH molecules below 0.5 langmuir exposures completely dissociate to generate ethylene and acetaldehyde via the intermediate of ClCH2CH2O-. The computational studies predict that the ClCH2CH2O- is most likely to be adsorbed at the 4-fold hollow sites of Cu(100), with its C-O bond only slightly titled away from the surface normal and with a gauche conformation with respect to the C-C bond. The hollow-site ClCH2CH2O- has an adsorption energy that is 4.4 and 19.2 kcal x mol(-1) lower than that of the ClCH2CH2O- bonded at the bridging and atop sites, respectively. No significant effect of precovered oxygen on the ClCH2CH2O- bonding geometry and infrared band frequencies has been observed, as compared with the case without oxygen.