Bounds to electron-pair relative and center-of-mass radii in many-electron atoms

When the electron-electron interaction is explicitly considered in many-electron atoms, the average electron radius (r) splits into the inner (r<) and outer (r>) radii. It is shown that the sum and difference of these radii constitute upper and lower bounds, respectively, to the electron-pair relative distance r(12)=(/r1-r2/). An analogous result is also derived for the electron-pair center-of-mass radius (R)=(/r1+r2//2). For the 102 atoms He through Lr in their ground states, the tightness of these bounds is numerically examined at the Hartree-Fock limit level. Good linear correlations are observed between (r12) and (r>), and between (R) and (r>)/2.     

Even-tempered Roothaan-Hartree-Fock wave functions for the third- and fourth-row atoms

Summary Roothaan-Hartree-Fock wave functions composed of 12s8p6d, 12s10p6d, and 12s10p8d even-tempered (ET) Slater-type functions (STFs), respectively, are reported for the atoms K-Zn, Ga-Kr, and Rb-Xe in their ground state. Despite the limited variational freedom in the Et method, the resultant atomic energies are found to compare well with fully-optimized wave functions of similar sizes. In particular, the present ET results reproduce almost completely the fully-optimized Sekiya-Tatewaki energies with the same basis set size for the atoms K-Zn. All the present energies are also lower than the Clementi-Roetti ones with slightly smaller but fully-optimized basis sets. A generalized even-tempered scheme is suggested and shown to give good results for Xe.     

Cation-exchange reaction with accompanying current discharge

When a cation-exchange membrane swollen with propylene carbonate was placed in tight contact with lithium foil, an ion-exchange reaction of lithium ions with the cation-exchange membrane occurred. The assembly exhibited properties of a lithium cell (3.0-3.2 V without load). The ion-exchange capacity of various cation-exchange membranes and their degree of swelling with propylene carbonte were related to the capacity of the formed lithium cell. A discharge current of 0.32 mA was observed through a 3 cm² cell. Analysis of lithium ions in the membrane phase after discharge revealed that the ion-exchange reaction of lithium ions with the cation-exchange groups of the membrane was directly related to the current discharge of the cell. However, the formed lithium cell showed high self-discharge.     

Carbon-13 spin-lattice relaxation study of linear polymers in solution

Proton-decoupled, partially relaxed, Fourier-transform NMR of ¹³C in natural abundance was used to determine spin-lattice relaxation times of individual carbons of polyisobutylene, polyacrylonitrile, poly(vinyl chloride), and poly(vinyl alcohol) in solution. It is shown that the relaxation times are independent of the difference in stereochemical configuration. From the values of the nuclear Overhauser enhancement factor it is shown that the relaxation times are independent of the difference in stereochemical configuration. From the values of the nuclear Overhauser enhancement factor it is shown that the excess spin energy from equilibration of all the ¹³C, even of quaternary carbons, in the polymers dealt with here is transferred to the lattice mainly through ¹³C-¹H dipolar interactions. It is shown that the segmental motions responsible for the spin-lattice relaxation of the polymer skeleton in solution can be described by the isotropic model within a good approximation, except for poly(vinyl alcohol) at low temperature. The activation energies of skeletal and internal methyl motions are estimated from the temperature dependence of the correlation time. Differences in the ¹³C line widths for individual carbons of polyisobutylene are discussed briefly.     

Photorefractive multiple quantum wells at 1064 nm

We have fabricated photorefractive InGaAs/GaAs multiple quantum wells that are sensitive at wavelengths near 1.06 mum for what is believed to be the first time. We have measured four-wave-mixing diffraction efficiency, using a Nd:YAG laser. A maximum diffraction efficiency of 7 x 10(-4) and a cutoff grating period of ~2 mum are obtained.     

13C-NMR-chemische Verschiebungen und stereochemische Strukturen im Polyvinylchlorid

Ohne Zusammenfassung     

Catalysis of α,β-elimination of serine by pyridoxal phosphate–metal-ion-quaternized poly(4-vinyl pyridine) system. A serine dehydratase model

The effect of quaternized poly(4-vinyl pyridine)(QPVP) on the α,β-elimination of series catalyzed to pyridoxall (PL) or pyridoxal phosphate (PLP) and metla ions was investigated. In PLP-Al³⁺ and PLP-Fe³⁺ systems QPVP showed simulation of about forefold; this stimulation was reduced in the presence of 0.5 M KCI. The catalytic activities of PL-Al³⁺ and PL-Fe³⁺ were lower compared to the corresponding PLP systems; stimulation by QPVP was also seen, through the extent of stimulation was smaller. The contribution of the electrostatic force between the polymer and the metal complex of the Schiff base was suggested to account for the stimulation. The pyridine moiety on the partialy quaternized PVP did not seen toparticpate in the catalysis. In PLP-Cu²⁺, PL-Cu²⁺, and PLP-VO²⁺ systems, however, QPVP showed marked inhibition. This inhibition by QPVP was also mitigated in the presence of 0.5 M KCl.