Thin-layer chromatographic behaviour and separation of rare earths in silica gel-aqueous alkali metal chloride systems

Summary The thin-layer chromatographic behaviour of all the rare earths except Pm on silica gel in aqueous solutions of five alkali metal chlorides has been surveyed. The Rf-values and the logarithms of the separation factors relative to Gd vary in a regular and peculiar way with increasing atomic number, through a reflection of the strong tetrad effect. A discussion concerning the effects on the Rf-values of the solvent cations and the solvent anions, and typical chromatograms for the separations of multi-component mixtures containing adjacent lanthanoids are also presented.     

Core-level photoemission of the Si(1 1 1)– -Ag surface using synchrotron radiation

The evolution of Si 2p core-level photoemission during a structural conversion from the Si (1 1 1)– -Ag to the Si(1 1 1)– -Ag superstructures induced by Ag adatoms adsorption at 140 K was studied using synchrotron radiation. The component from the top-layer Si-trimer atoms on the former surface was found to split into two components in the latter surface. The result is discussed in terms of a relaxation in some of the Si trimers induced by Ag adatoms sitting on the nearby Ag triangles of the -Ag substrate. The intensity ratio between the split components is a key to exclude some structure models proposed so far for the phases.     

Performance Change of the Oxidative Coupling of Methane Induced by the Modification Effect of Lithium on a Mn-Mg-O Solid Solution

Lithium made a Mn-Mg-O solid solution stable upon exposure of methane, decreased the ethane and ethylene formation rates, and increased the COx formation rate during the oxidative coupling of methane. On the other hand, on MgO, lithium inhibited COx formation markedly and enhanced the selectivity of ethane 47% to 76%.     

Simultaneous Amplification of Terahertz Difference Frequencies by an Injection-Seeded Semiconductor Laser Amplifier at 850 nm

Two-frequency operation of an 850 nm semiconductor optical amplifier was achieved by simultaneously injection seeding it with two diode lasers. The two frequencies could be independently amplified without strong interference when they were separated by more than 10 GHz, and the spectral purity was preserved by the amplification process. At frequency differences below 10 GHz, unbalanced two-frequency output was observed, which can be explained by a two-mode interaction driven by the refractive index modulation at the beat frequency. The laser system is suitable for the difference-frequency generation of coherent terahertz radiation in ultra-fast photoconductors or nonlinear optical media.     

Subpicosecond photon echoes by using nanosecond laser pulses

Subpicosecond time resolutions have been obtained in photon echoes when a sample was excited by two nanosecond dye laser pulses with a smooth and broad spectrum. The dye laser was pumped by second harmonics of a Q-switched Nd:YAG laser, and the pulse width was 10 ns. The sample was 3% Nd³⁺-doped silicate glass, and the center frequency of the dye laser was tuned at 5910 Å on resonance with the ⁴I_{$\text{9}\text{2}$} ? ²G_{$\text{7}\text{2}$}, ⁴G_{$\text{5}\text{2}$} transition of Nd³⁺. The homogeneous transverse relaxation time T₂ was measured to be 91 ps at 10 K in agreement with the previous measurements by picosecond pulses.     

A new synthesis of olefins. Conversion of nitroolefins into olefins by reductive elimination

A nitro group in nitroolefins is displaced by hydrogen giving the corresponding olefins in good yields by the reaction of nitroolefins with sodium sulfide in the presence of benzenethiol. It proceeds rapidly at room temperature.     

Microwave spectroscopy of the CCl radical

The CCl radical was generated by a dc glow discharge in CCl₄, and rotational transitions of C³⁵Cl in both ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ were observed in the mm-wave region by using a source modulation microwave spectrometer. From an analysis of the observed spectra the magnetic and electric quadrupole hyperfine coupling constants of the ³⁵Cl nucleus were determined precisely. The Λ-doubling constant p₀ was determined to be positive, indicating that unknown ²Σ^? excited electronic states are making dominant contributions to the Λ doubling in the ground state. The previous diode-laser result [J. Mol. Spectrosc.85, 416–426 (1981)] was reanalyzed by using improved wavelength standards and by fixing the ground-state parameters to the present microwave values including the B₀ rotational constant 20 797.1725(38) MHz. The vibration-rotation constant α^B and the equilibrium bond length r_e were thus determined to be 0.006 768 2(48) cm^?1 and 1.645 218(16) Å, respectively, with 2.5 times standard deviations in parentheses. The spin density on the chlorine atom was estimated to be about 0.20 from the observed hyperfine coupling constants.