The cleavage-face of a sodim-β-alumina crystal was studied by means of X-ray photoelectron spectroscopy (XPS). A detailed quantitative analysis, which took into account the particular layered structure in this crystal, revealed a significantly (≈50%) Na deficient surface produced by cleaving the crystal along a conduction plane. The expressions derived for the elemental composition are applicable to any layered structure. Ion sputtering of the cleavage surface caused atom mixing in the layered structure as well as a preferential removal of the mobile sodium ions. Auger electron spectroscopy (AES) measurements showed that unlike the cleavage surface, the edge surface contains a significantly high concentration of sodium. 相似文献
Equilibrium structures and force constants for skeletal bending from linearity have been calculated, in the MNDO approximation, for twenty five singlet carbenes CX2. When the substituent X bears neither vacant orbitals nor lone pairs, the force constant becomes steadily more negative as the electronegativity of X increases; when X bears vacant orbitals, the C→ X π bond order and the force constant both increase with the electronegativity of X. When X bears lone pairs, the force constant parallels the HOMO—LUMO gap at linearity. Previous discussions of the structures of singlet carbenes are shown to be inadequate: the reported results support the interpretation in terms of the second-order Jahn-Teller effect of the observed stereochemical inactivity of lone pairs in the presence of ligands of low electronegativity. 相似文献
The energy transfer phenomenon has been studied from Tb3+ → Nd3+ and Tb3+ → Ho3+ in DMSO. A diffusion limited dipole-dipole mechanism of energy transfer is suggested for both systems. At high acceptor concentrations, Pda depends linearly on C2 consistent with the Fong and Diestler theory of energy transfer. However, at low acceptor concentrations the observations of time evolutions of Tb3+ luminescence decay following flash excitation has enabled us to examine diffusion limited energy transfer from Tb3+ to Nd3+ and Tb3+ to Ho3+ in DMSO. 相似文献
The coupling of atomic and photonic resonances serves as an important tool for enhancing light‐matter interactions and enables the observation of multitude of fascinating and fundamental phenomena. Here, by exploiting the platform of atomic‐cladding wave guides, the resonant coupling of rubidium vapor and an atomic cladding micro ring resonator is experimentally demonstrated. Specifically, cavity‐atom coupling in the form of Fano resonances having a distinct dependency on the relative frequency detuning between the photonic and the atomic resonances is observed. Moreover, significant enhancement of the efficiency of all optical switching in the V‐type pump‐probe scheme is demonstrated. The coupled system of micro‐ring resonator and atomic vapor is a promising building block for a variety of light vapor experiments, as it offers a very small footprint, high degree of integration and extremely strong confinement of light and vapor. As such it may be used for important applications, such as all optical switching, dispersion engineering (e.g. slow and fast light) and metrology, as well as for the observation of important effects such as strong coupling, and Purcell enhancement.
Starting from readily available oleic and erucic acid, macrocyclic nonadecalactone (C19) and tricosalactone (C23) can be synthesized in polymerization grade purity in a four‐step reaction sequence. Ring‐opening polymerization (ROP) of these strainless macrolactones can be performed utilizing an enzyme as a catalyst. Despite the missing ring‐strain as key driving force for smaller (strained) lactones, high molar masses (M n ≈ 105 g mol−1) can be accessed in an entropically driven ROP. Polyester‐19 and polyester‐23 prepared feature melting temperatures well above 100 °C. Further analysis of the mechanical properties of these materials displays the resemblance to polyethylene. For example, Young's moduli on the order of 600 MPa are observed as a result of the high crystallinity of the polymer.
A finite element analysis was performed to simulate crack tip blunting and the development of the intense strain region in a small compact tension specimen (0.4 T CT) of SA533B-1 under plane strain large-scale yielding, with the condition of large-geometry change around the crack tip taken into consideration. The region where the equivalent plastic strain g3p is greater than 0.15 was defined as the intense strain region, which corresponded to the recrystallized-etched zone delineated experimentally around the blunting crack tip. The development of the intense strain region was discussed as a function of the J-integral and the crack opening displacement. A linear relationship was obtained between the plastic work Wp dissipated within the intense strain region and (J/σy)2 or b2, where b is the crack opening displacement, defined as the separation of the two points at which the boundary of the intense strain region surrounding the crack tip intersects with the free surfaces of the crack. 相似文献
Ni20[(OH)12(H2O)6][(HPO4)8(PO4)4]·12H2O nanorods are successfully synthesized via a one‐pot hydrothermal reaction. A high‐performance flexible asymmetric all‐solid‐state supercapacitor based on the obtained Ni20[(OH)12(H2O)6][(HPO4)8(PO4)4]·12H2O nanorods (positive electrode) and graphene nanosheets (negative electrode) is successfully assembled. It is the first report of this nanomaterial applied for all‐solid‐state supercapacitors. Interestingly, a maximum volumetric energy density of 0.446 mW h cm?3 at a current density of 0.5 mA cm?2 and a maximum power density of 44.1 mW cm?3 at a current density of 6.0 mA cm?2 are achieved by the as‐assembled device. What's more, the device also shows excellent mechanical flexibility and little capacitance change after over 5000 charge/discharge cycles at a current density of 0.5 mA cm?2. 相似文献