Structure of dichlorine monoxide as studied by microwave spectroscopy. Determination of equilibrium structure by a modified mass dependence method

The microwave spectra of four isotopic species of dichlorine monoxide (OCl₂) have been observed, and the rotational constants have been obtained. The r_m structure for each isotopic species has been determined by Watson's method. The equilibrium structure has been estimated by taking proper averages of r_m structures to be $\text{r}{}_{\mathrm{e}}\text{(OCl) = 1.69587(7)}\text{A}\text{?}$ and ∠_eClOCl = 110.886(6)°. The general applicability and the merit of the present method for estimating the equilibrium structure are pointed out.     

Bilepton production in $ e^-\gamma $ collisions

We study the production of bileptons, new gauge bosons of lepton number two, in the minimal 3-3-1 model in high energy collisions. If the bilepton masses are in the range of 300 GeV the reaction will give observable cross-sections in future colliders.Received: 5 August 2003, Published online: 23 March 2004Dang Van Soa: On leave of absence from Department of Physics, Hanoi University of Education, Hanoi, VietnamHoang Ngoc Long: On leave of absence from Institute of Physics, NCST, P.O. Box 429, Bo Ho, Hanoi 10000, Vietnam     

Formation and atomic structures of boron nitride nanohorns encaging boron nitride cluster

Boron nitride (BN) nanohorns were synthesized by arc-melting YB₆ powders. Method, and atomic structure models for BN nanohorns encaging Y@B₃₆N₃₆ were proposed from high-resolution electron microscopy. The molecular mechanics calculation indicated that BN clusters with metal atoms would be stabilized by being encaged in double-walled BN nanohorns.     

WIDE RANGE DETECTOR USING PARABOLIC CYLINDRICAL MIRROR FOR THz APPLICATIONS

A new, wide-band, high-speed and high-sensitivity THz detector has been developed. The prototype detector consists of a parabolic cylindrical mirror, a long wire antenna and a Schottky barrier diode. Direct detection measurements have shown a stable sensitivity of 150 ± 50 V/W for 1–2 THz without any adjustments. The long wire antenna was fixed at the focus of parabolic cylindrical mirror then it has been realized less operation steps, easy coupling to the external THz signals and a dramatic enhancement in the practicality of this system. The optically polished mirror and frosted surface one showed comparable sensitivities, thus easy polishing and less cost mirror fabrication can be applied for this system. The radiation pattern showed a maximum radiation angle of approximately 23° with its dominant main lobe, which was attributed to the wire antenna character and confirmed good agreements with classical antenna theory.     

Domain walls and gravitational waves after thermal inflation

Thermal inflation is an attractive solution to the cosmological moduli problem. However, domain walls may be formed after thermal inflation and some mechanisms are needed to eliminate the domain wall before it dominates the Universe. We point out that gravitational waves produced by the dynamics of domain walls may be observed by the pulsar timing experiments and future space-borne gravitational wave detectors, which provides a probe into the period of thermal inflation. We also show that the QCD instanton effect can effectively eliminate the domain walls with producing observable amount of gravitational waves.     

Preparation of Ca(1−x)EuxGa2S4 crystals and their photoluminescence, absorption and excitation spectra

The single crystal of CaGa₂S₄:Eu is expected as a useful laser material with a high quantum efficiency of light emission. However, as far as our knowledge is concerned, the systematic study of the mixed compounds of Ca_(1−x)Eu_xGa₂S₄ as a function of x has not been reported up to now. Here, we have first constructed the phase diagram of the CaGa₂S₄ and EuGa₂S₄ pseudo binary system, and show that it forms the solid solution. Then we have grown single crystals of these compounds. The maximum photoluminescence efficiency is achieved at x=0.25. From the three peak energies observed in the photoluminescence excitation (PLE) and absorption spectra, the 5d excited states are suggested to consist of three levels arising from the multiplets of Eu²⁺ ions.     

Polymerization of Cyclic Ethers

Abstract

In the present series of studies on the cationic polymerization of cyclic ethers, the reactivities of cyclic ethers were quantified and the effect of the catalyst upon the polymerization kinetics was revealed. These kinetic analyses were successfully performed by means of our “phenoxyl end-capping method”. The change of the reactivity by the ring size of the monomer was interestingly demonstrated. In addition, it is emphasized that the frequency factor as well as the activation energy influence the rate constant of propagation. As to the effect of catalyst upon the polymerization kinetics, the most important conclusion is that the rate constant of propagation changes very little according to the changes of the catalyst components. Variation of the conversion rate by a change of catalyst is due to differences in the rates of the initiation and the termination reactions.     

Synthesis and Polymerization of Spiro Oxyphosphoranes

Novel methods of synthesis of spiro acyloxyphosphoranes are described emphasizing the significance of the first isolated instance of these new species. Then, the no-catalyst alternating copolymerizations of the combinations of cyclic phosphorus(III) compounds (serving as nucleophilic monomer, M_N) with acrylic acid derivatives and with α-keto acids (electrophilic monomer, M_E) are mentioned. These copolymerizations proceed without added initiator. Spiro oxyphosphoranes play an important role in the copolymerization scheme in the equilibrium with the ⁺M_N - M_E ^? zwitterion, the key intermediate of the copolymerization. Finally, new reactions of spiro acyloxyphosphoranes with nucleophiles, alcoholysis and aminolysis polymerizations are presented.     

1,4-Addition of silicon dienoates to α,β-unsaturated aldehydes catalyzed by in situ-generated silicon Lewis acid

In situ-generated silyl methide species (R(3)Si-CTf(2)R') effectively catalyzed the reaction of β-substituted α,β-unsaturated aldehydes with silicon dienoates such as 3-bromo-2-TESO-furan to give the corresponding γ-adducts with excellent 1,4-selectivity and good anti selectivity.