Vacuum ultraviolet (147 nm) photolysis of 1,2-fluorochloroethane

1,2-Fluorochloroethane was photolyzed at 147 nm in the pressure range of 3.8–20.9 torr. The effects of added NO, H₂S, and large pressures of CF₄ were also investigated. The exponential extinction coefficient at 147 nm and 296°K was found to be 147 ± 4 atm^?1 · cm^?1. The photochemistry in some respects is similar to that of ethyl chloride. The primary processes again appear to involve at least two excited states. One of these yields ethylene by FCl elimination (Φ ? 0.3) and has a lifetime of ～3.2 × 10^?10 sec, with respect to an internal conversion to the vibrationally excited ground state or, more probably, a collisionally induced crossover to a state decomposing mainly by carbon? halogen bond fission. The molecular elimination of HCl, H₂, and small amounts of HF also occurs but not apparently from the same state as does FCl. The quantum yields of products with radical precursors, however, are not large, and hence little, if any, of the FCl and probably none of HCl, H₂, and HF subsequently dissociates. The vinyl fluoride and vinyl chloride, accompanying the elimination of HF and HCl, are postulated as possible sources of the secondary production of acetylene.     

On a Theorem of Childs on Normal Bases of Rings of Integers: Addendum

Let p 3 be a prime number, F be a number field with _p F^x,and K = F(_p). In a previous paper, the author proved, undersome assumption on p and F, that an unramified cyclic extensionN/F of degree p has a normal integral basis if and only if thepushed-up extension NK/K has a normal integral basis. This addendumshows that the assertion holds without the above-mentioned assumption.     

Quantitative evaluation of spatial coherence of the electron beam from low temperature field emitters

By using multiwalled carbon nanotubes as an element of a nanobiprism, we evaluated quantitatively the coherence of electrons emitted from tungsten tips at room temperature and 78 K, and found an enhancement of coherence at 78 K. The increase of the transverse coherence length of the electron beam agreed well with that of the inelastic mean free path of electrons in solids, demonstrating the direct relationship between the coherences of the electron beam and the original electronic states. On the basis of this experimental fact, we comment on the interpretation of recent Hanbury Brown-Twiss type experiments for electrons reported by Kiesel et al. [Nature (London) 418, 392 (2002)]].     

Enhancement of pionic modes in the quasielastic region

We report an evidence for the precursor phenomena of the pion condensation, which is found in the enhancement of the spin longitudinal cross sections ID _q of the quasielastic ¹²C, $^{40} Ca(\vec p, \vec n)$ , reactions at the incident energy 494 and 346 MeV around the momentum transfer q ≈ q _c , the critical momentum of the pion condensation. We utilized the distorted wave impulse approximation incorporated with the continuum random phase approximation. We adjusted the Landau-Migdal parameters, g′ _NN and g′ _NΔ, and obtained g′ _NN ≈ 0.6–0.7 and g′ _N Δ ≈ 0.3–0.4, which are consistent with those obtained from the energy of the Gamov-Teller giant resonance and the quenching factor of the Gamov-Teller sum rule.     

The leaching behavior of PbOSiO2 glasses

The leached layer of PbOSiO₂ glasses formed by diluted nitric acid solution has been investigated by ellipsometry and Auger electron spectroscopy (AES). The leaching behavior of PbOSiO₂ glasses in 10^?4 N aqueous solution of NHO₃ at 30°C was measured in real time using a Nikon auto-ellipsometer.The results were applied by curve fitting to the two-layer model from the concentration profile obtained by AES, and the refractive index profile against the film thickness was determined.The leached layer is inhomogeneous and consists of a low refractive index region and a transition region. The gradient of the refractive index in the former region is extremely small and the refractive index becomes nearly constant between 1.42 and 1.44. The shape of latter region becomes stable with its thickness at 100–310 Å, and moves in the direction of depth without changing the shape as the leaching proceeds.     

Command surfaces 12 [1]. Factors affecting in-plane photoregulation of liquid crystal alignment by surface azobenzenes on a silica substrate

In-plane alignment of nematic liquid crystals was regulated by polarized-light-irradiation of a cell assembled with a silica plate, the surface of which was modified by attaching 4-hexyl-4'-hexyloxyazobenzene at its o-position through surface silylation. The photoisomerizability of the chemisorbed azo-chromophore was affected by their surface density and the nature of photoinactive co-modifiers. The efficiency of the photoregulation of liquid crystal alignment was optimized by two-dimensional dilution of the chromophore with ethyltriethoxysilane (ETS) or 3-aminopropyltriethoxysilane (ATS). As a result, favourable procedure was to modify a silica surface with a crude azo-silylating reagent contaminated by ATS. The rate of the photoinduced reorientation of liquid crystals was followed by monitoring the alteration of the alignment direction of a dichroic dye dissolving in a mesophasic layer upon exposure to linearly polarized light. Exposure energy for the in-plane reorientation of a liquid crystal was about 100mJcm^-2 of 445 nm light at elevated temperatures close to T_NI. The effect of positional isomerism on the photoregulation was determined with the use of 4-cyano-4'-hexyloxyazobenzene as a commander molecule. It was confirmed that the photoalignment efficiency was markedly enhanced by attaching the chromophore at the ortho- or meta-position. The exposure energy for the reorientation of a liquid crystal was reduced by linking the p-cyanoazobenzene at the meta-position so that the reorientation was complete with an exposure energy of 20mJcm^-2.     

Synthesis and properties of new chiral dopants containing a δ-lactone ring for practical ferroelectric liquid crystal mixtures

A series of new optically active δ-lactones were synthesized as chiral dopants for ferroelectric liquid crystals (FLCs). The response time of an FLC mixture containing 4 mol% (S)-2,2-dimethyl-5-[2-fluoro-4-(5-n-octylpyrimidin-2-yl)-phenoxy[methyl-δ-valerolactone was 25 μs at 25°C. (0-90 per cent change in light transmission, 10 V μm^-1). The synthesis and properties of these materials as practical chiral dopants are reported.     

Tripod self-assembled monolayer on Au(111) prepared by reaction of hydroxyl-terminated alkylthiols with SiCl4

Infrared reflection spectroscopy (IRS), single wavelength ellipsometry, and density functional theory were used to elucidate the structure of a molecular tripod self-assembled monolayer (SAM) on polycrystalline gold{111} substrates. The tripod SAM was formed by the reaction of SiCl4 with a densely packed monolayer of 2-mercaptoethanol, 6-mercaptohexanol, and 16-mercaptohexadecanol under inert atmosphere. After reaction with SiCl4, IRS spectra show an intense absorption at approximately 1112 cm(-1) that is attributed to Si-O-C asymmetric stretching vibration of a molecular tripod structure. Harmonic vibrational frequencies computed at the B3LYP/6-311+g** level of theory for the mercaptoethanol tripod SAM closely match the experimental IRS spectra, giving further support for the tripod structure. When rinsed with methanol or water, the Si-Cl-terminated SAM becomes capped with Si-OMe or Si-OH. The silanol-terminated tripod SAM is expected to find use in the preparation of thin zeolite and silica films on gold substrates.