Photoluminescence and luminescence excitation spectra in ZnSiP2

Summary Measurements of photoluminescence and luminescence excitation spectra of ZnSiP₂ have been performed at 4.2K and two results were obtained. One is the observation of a new sharp emission line at 1.980 eV, due to the bound exciton associated with the pseudodirect gap. The other is the observation of another new series of absorption lines in the luminescence excitation spectrum of an emission line, at 1.984 eV, in addition to those reported previously. These results indicate that in ZnSiP₂ radiative transitions occur at both the indirect and the pseudodirect gaps. Paper presented at the ?V International Conference on Ternary and Multinary Compound?, held in Cagliari, September 14–16, 1982.     

Mössbauer spectroscopic study on polyacetylene doped with iodine

The ¹²⁹I Mössbauer effect has been applied to polyacetylene films of cis-(CHI_0.23)_x as prepared and cis-(CHI_0.20)_x led under dynamic evacuation. It has been clarified that both films contain linear I^?₅ and I^?₃ with symmetric charge population and that the fraction of I^?₃ increases after evacuation. The mechanism of electrical conductivity in iodine-doped polyacetylene has been discussed on the basis of the chemical form and the dynamic behavior of the anion species.     

Anisotropic optical properties of pure and doped polyacetylene

Optical absorption and reflection measurements have been carried out on pure and doped polyacetylene films. The absorption data are consistent with a model of (CH)_X as a direct gap quasi-l d semiconductor; doping with AsF₅ or iodine introduces absorption within the gap, but appears to leave the interband transition intact. The anisotropic reflectance from partially aligned films and the increased optical anisotropy upon doping provide evidence of quasi-l d behavior of the semiconducting pure polymer and the metallic doped polymer.     

Magnetic properties and hydrostatic pressure effect on the curie temperature of (Co,Mn)2B amorphous alloys

The temperature dependence of magnetization and magnetic susceptibility and hydrostatic pressure effect on the Surie temperature (dT_c/dP) are measured for (Co_1-xMn_x)₂B (0?x?0.4) amorphous alloys and the results are compared with those of crystalline compounds with the same composition. The Curie temperature decreases linearly with an increasing Mn content but magnetization shows a maximum around x=0.15. The reciprocal magnetic susceptibility of all the prepared alloys obeys the Curie-Weiss law above T_c. The magnitude of the negative value of dT_c/dP decreases linearly with increasing x from about 1.1 K/kbar (x=0) to zero (x=0.4), the composition dependence of which is opposite to that of the crystalline compound. The composition dependence of the average magnetic moment per transition metal atom and the Curie temperature and dT_c/dP are analysed on the basis of the local environment and the pair order interaction mode, respectively.     

Arylmagnesiation of alkynes catalyzed cooperatively by iron and copper complexes

Iron and copper complexes cooperatively catalyzed the arylmagnesiation of unfunctionalized alkynes including dialkylacetylenes, where the presence of both iron and copper catalysts is essential for high yields of 2-aryl-1-alkenylmagnesium bromides.     

Alkynes as activators in the nickel-catalysed addition of organoboronates to aldehydes

Alkynes act not as substrates but as co-catalysts in the presence of a nickel catalyst, an organoboronate and an aldehyde to promote the addition reaction between the substrates in combination with H2O.     

Organogel of an 8-quinolinol platinum(II) chelate derivative and its efficient phosphorescence emission effected by inhibition of dioxygen quenching

A newly synthesized 8-quinolinol platinum(II) chelate derivative gelates various organic solvents, and the gel formed shows unique thermo- and solvatochromism of visible and phosphorescent colour in response to a sol-gel phase transition and possesses an attractive ability to inhibit dioxygen quenching of excited triplet states.     

Molecular defects of polyacrylonitrile formed in aqueous medium

The various kinds of molecular defect that are related to the thermal property of polyacrylonitrile (PAN) are studied in detail in relation to the polymerization mechanism in an aqueous medium. The existence of two different kinds of polymer radical is pointed out and the significance of polarity of radical species is emphasized. It is shown that the structural irregularity along the main chain is surely present but has little effect on the thermal property of PAN. It is estimated that one of the most significant defects relating to the thermal property is the main-chian type of branching the occurs predominantly in hydrogen on a polymer backbone. The relationship between activator (i.e., NaHSO₃) incorporation and branch inhibition mechanisms is discussed. The optimum polymerization condition, under which the highest thermal quality of molecules is obtained, is found empirically within a limited experimental range, for an aqueous heterogeneous system.