Stability test and improvement of hydrogen analyzer with trace reduction detector

We previously developed an analyzer able to detect hydrogen concentrations of less than 50 cm3/1000 m3. The analyzer uses a carrier gas purifier and a low temperature separation column to remove impurities preventing measurement of low concentrations from the carrier and sample gases. It uses a trace reduction detector with a mercuric oxide bed to detect the concentration of hydrogen based on the reduction reaction of mercuric oxide with hydrogen. We have now evaluated the performance of the analyzer by carrying out a series of tests that measured the spectrum peak and the retention time. We used three sample gases with hydrogen concentrations of 5, 20, and 50 cm3/1000 m3 in nitrogen dilution gas. The measured peak was stable (it was within a relative standard deviation of less than 10%), and there was a linear relationship between the peak and hydrogen concentration. However, the retention time gradually shortened as the measurements were repeated. The shortening was reduced by warming the low temperature separation column used in the analyzer; it was not observed when we used a hydrogen sample gas diluted by helium instead of nitrogen. Using nitrogen as a dilution gas apparently shortens the retention time. We thus added an MS-5A separation column and a thermal conductivity detector. The nitrogen and hydrogen in the sample/carrier gas are separated, and the nitrogen is efficiently removed by switching the pass line to a release line after the hydrogen has been sent to the low temperature separation column. An analyzer using this "after-cut method" was able to stably measure infinitesimal hydrogen concentrations and was not affected by nitrogen in the sample gas.     

An evolved explanation for the molecular geometry and electronic structure of diphenyl-substituted cyclic trimethylenemethane in the ground state: a nearly planar conformation with a considerably localized electronic state

[structures: see text] We reinvestigated the molecular geometry and electronic structure of the diphenyl-substituted, five-membered cyclic trimethylenemethane (TMM) diradical (Berson's TMM, 3**) using UV/VIS absorption and emission spectroscopy combined with density functional theory (DFT) and time-dependent (TD)-DFT calculations. Two intense absorption bands, A and B, with lambda(ab) at 298 and 328 nm, respectively, a weak absorption band C, with lambda(ab) at 472 nm, and an intense emission band D, with lambda(em) at 491 nm, were observed for 3**. By comparing the spectrum of 3** with those of the 1,1-diphenylethyl (7*) and cyclopent-2-en-1-yl (9*) radicals, it was found that bands B, C, and D originated from the diphenylmethyl radical moiety (subunit I), while band A should most likely be assigned to an electronic transition related to an interaction between subunit I and residual subunit II, the cyclopentenyl radical moiety. An UB3LYP/cc-pVDZ calculation indicated that, in the ground state, the two unpaired electrons of 3** are mainly localized in subunits I and II, respectively, and the interaction between them is inefficient, despite the nearly planar conformation (theta = +23.5 degrees). Furthermore, a TD-UB3LYP/cc-pVDZ calculation suggested that absorption band A is assigned to an electronic transition involved with enhancement of the electron density of the C-2-C-3 bond. Substituent effects on the absorption and emission spectra of 3** using 11** and 13** support the conclusion based on the experiments and calculations. Therefore, we propose an evolved explanation for the molecular geometry and electronic structure of the ground state of 3** in a low-temperature matrix, a nearly planar conformation with a considerably localized electronic state, which alone accounts for the spectroscopic characteristics.     

Creation of Polymerizable Species in Plasma Polymerization

Plasma polymerization of trimethylsilane (TMS) was carried out and investigated in a direct current (dc) glow discharge. The formation of TMS plasma glow was carefully examined with optical photography as compared with an Ar dc glow discharge. It was found that there exists a significant difference in the nature of glow and how the glow is created in TMS glow discharge, which polymerizes or causes deposition, and that of monatomic gas such as Ar, which does not polymerize or deposit. In dc Ar discharge, the negative glow, which is the most luminous zone in the discharge, develops in a distinctive distance away from the cathode surface, and the cathode remains in the dark space. In a strong contrast to this situation, in TMS dc discharge, the primary glow that is termed as cathode-glow in this paper appears at cathode surface, while a much weaker negative glow as a secondary glow was observed at the similar location to where the Ar negative glow appears. The deposition results of plasma polymers and gas phase composition data of TMS in a closed reactor acquired by ellipsometry and residual gas analyzer (RGA) measurements clearly indicated that the cathode-glow in TMS glow discharge is mainly associated with chemically reactive species that would polymerize or form deposition, but the negative glow is related to species from simple gases that would not polymerize or deposit. Based on the glow location with respect to the cathode, it was deduced that the cathode-glow is due to photon emitting species created by molecular dissociation of the monomer that is caused by low energy electrons emanating from the cathode surface. The negative glow is due to the ionization and the formation of excited neutrals of fragmented atoms caused by high-energy electrons. Polymerizable species that would cause deposition of material (plasma polymers) are created mainly by the fragmentation of monomer molecules by low energy electrons, but not by electron-impact ionization of the monomer.     

High quality a-Si film produced by horizontal plasma furnace

A series of investigation on the a-Si film quality in a p-i-n junction has been made by employing the separated three chamber system of horizontal plasma mode. A clear improvement of film quality has been experimentally verified in a-Si films prepared by this system as compared with those by the single chamber system. On the basis of these investigation, a-SiC/a-Si/μc-Si heterojunction solar cells having more than 9% conversion efficiency have been developed.     

Experimental investigation of the closest parallel pulses in holographic femtosecond laser processing

In holographic femtosecond laser processing, diffractive parallel pulses are distorted by phase discontinuities and mutual interference between the neighborhoods in the reconstructed image of a Fourier computer-generated hologram when the interval is smaller than the beam diameter. We investigated holographic fabrication on a glass surface using parallel pulses with different intervals. We found the closest parallel pulses with sufficient separation to avoid mutual interference in holographic femtosecond laser processing. The minimum interval was 2.8 times larger than the diffracted beam diameter. The experimental results were also supported by a computer simulation. Our findings will be very useful in the design of holographic laser processing systems.     

Syntheses and Fully Diastereospecific Photochromic Reactions of Thiophenophan‐1‐enes with Chiral Bridges

Thiophenophan‐1‐enes with chiral polyether bridges were prepared and their diastereospecific photochromic reactions were studied. The coupling reaction of substituted dithienylethenes and various chiral synthons afforded thiophenophan‐1‐enes, namely, bridged dithienylethenes, as single enantiomers without optical resolution, thus indicating that these reactions occurred diastereoselectively. Upon UV irradiation, each optically active thiophenophan‐1‐ene isomerized to the corresponding enantiomer of the closed form and returned to the initial enantiomer of the open form upon visible irradiation. Because thiophenophan‐1‐enes never isomerized to other diastereomers even at a high temperature, they underwent diastereospecific photochromic reactions. Large changes were observed in the measurement of the optical rotations of the solutions of thiophenophan‐1‐enes at 588 nm according to their photochromic reactions. As there was no absorption at this wavelength for both isomers of each thiophenophan‐1‐enes, the nondestructive readout of the photochromic reaction could be carried out by using these chiral thiophenophan‐1‐enes.     

Syntheses and fully diastereospecific photochromic reactions of thiophenophan-1-enes with chiral bridges

Thiophenophan-1-enes with chiral polyether bridges were prepared and their diastereospecific photochromic reactions were studied. The coupling reaction of substituted dithienylethenes and various chiral synthons afforded thiophenophan-1-enes, namely, bridged dithienylethenes, as single enantiomers without optical resolution, thus indicating that these reactions occurred diastereoselectively. Upon UV irradiation, each optically active thiophenophan-1-ene isomerized to the corresponding enantiomer of the closed form and returned to the initial enantiomer of the open form upon visible irradiation. Because thiophenophan-1-enes never isomerized to other diastereomers even at a high temperature, they underwent diastereospecific photochromic reactions. Large changes were observed in the measurement of the optical rotations of the solutions of thiophenophan-1-enes at 588?nm according to their photochromic reactions. As there was no absorption at this wavelength for both isomers of each thiophenophan-1-enes, the nondestructive readout of the photochromic reaction could be carried out by using these chiral thiophenophan-1-enes.     

The alpha effectiveness of the dating ESR signal in barite

The alpha effectiveness was investigated for an ESR signal due to ${\text{SO}}_3^{?}$ in barite by comparing the dose responses of the signal for gamma irradiation and for He ion implantation with an energy of 4 MeV. The value was obtained to be 0.043 ± 0.018 for samples from Morocco and to be 0.0089 ± 0.0006 for Kanehira Mine. The dose response for He ion implantation for the latter sample better fits to a correlation line but the signal shape changes with gamma ray dose, indicating contribution from an unknown radiation sensitive signal, while the former sample shows the same signal shapes. A value of 0.043 ± 0.018 is adopted as the alpha effectiveness of ${\text{SO}}_3^{?}$ signal in barite, which is used for ESR dating of submarine hydrothermal activity.