Preparation of cold ions in strong magnetic field and its application to gas-phase NMR spectroscopy

Nuclear Magnetic Resonance (NMR) technique is widely used as a powerful tool to study the physical and chemical properties of materials. However, this technique is limited to the materials in condensed phases. To extend this technique to the gas-phase molecular ions, we are developing a gas-phase NMR apparatus. In this note, we describe the basic principle of the NMR detection for molecular ions in the gas phase based on a Stern-Gerlach type experiment in a Penning trap and outline the apparatus under development. We also present the experimental procedures and the results on the formation and the manipulation of cold ions under a strong magnetic field, which are the key techniques to detect the NMR by the present method.     

A single-phase PCS with a novel constantly sampledcurrent-regulated PWM scheme

The error-tracking mode (ETM) is a novel constantly sampled pulsewidth modulation (PWM) scheme for a voltage-source power conversion system (PCS) interconnecting with a utility network to regulate its AC current waveform. It guarantees, theoretically, the AC actual current to be settled within an arbitrary target allowable error. Generated current harmonics can be restricted by a relatively small filter. Both the minimum on- and off-duration times of switching commands are assured by the PWM scheme itself. A four-quadrant 1-kVA PCS in which gate commands are produced by the novel PWM scheme has been successfully experimented upon for the first time, and it has justified the ETM-PWM theory. This paper describes the design procedure and experimental results of the trial setup     

Pervaporation properties of crosslinked poly(dimethylsiloxane) membranes for the removal of hydrocarbons from water

The pervaporation (PV) performance of crosslinked poly(dimethylsiloxane) dimethylmethacrylate (PDMSDMMA) membranes for an aqueous solution of various hydrocarbons was studied using sorption–diffusion theory. Three chlorinated hydrocarbons (chloroform, trichloroethylene, and tetrachloromethane) and three aromatic hydrocarbons (benzene, chlorobenzene, and toluene) were used as the permeants. When aqueous solutions of 0.05 wt % hydrocarbon were permeated through the crosslinked PDMSDMMA membranes, they showed high hydrocarbon/water selectivity and permeability during PV. The hydrocarbon/water selectivity of the crosslinked PDMSDMMA membranes was significantly dependent upon the permeants; in particular, chloroform removed the hydrocarbons most efficiently in this study. The results of the temperature dependence of the PV performance and hydrocarbon absorption into the membrane revealed that the difference in hydrocarbon/water selectivity for various aqueous solutions of hydrocarbons during PV depended significantly on the molar volume and diameter of the hydrocarbons. The permeation and removal mechanism of hydrocarbons from water through crosslinked PDMSDMMA membranes can be explained by a qualitative model based on the diffusion jump model. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2079–2090, 2006     

Electrical activation of phosphorus-donors introduced in 6H-SiC by hot-implantation

Phosphorus ion (P⁺) implantations into 6H-SiC at room temperature (RT), 800 °C, and 1200 °C with mean concentrations of 1᎒¹⁸-5᎒¹⁹ /cm³ were performed to investigate the effects of hot-implantation on the electrical activation of P atoms. Improvement of the electrical activation of P atoms due to hot-implantation is found to depend on their implantation concentration, which can be divided into three regions. In the implantation with P in a low-concentration region (for example, 1᎒¹⁸ /cm³), no significant difference in the carrier concentrations among the samples implanted at RT and elevated temperatures is observed after annealing above 񫰸 °C. In a medium-concentration region, the carrier concentration increases with implantation temperature. When P ions were implanted in a high-concentration region (for example, 5᎒¹⁹ /cm³), the hot-implanted samples exhibit higher carrier concentration as compared with RT-implanted samples. Regarding hot-implantation, the carrier concentration in 800 °C-implanted samples is higher than that in the 1200 °C-implanted samples. This results can be interpreted as a degree of damage introduced by each implantation.     

Characteristics of a cw monolithic optical parametric oscillator

4 as a nonlinear crystal and obtained a pump threshold of 7 mW and an output power of 6 mW for a pump power of 40 mW. The OPO operated in a single longitudinal mode pair of a signal and an idler, over 1 h without mode hopping in the free-running condition. The signal and the idler wavelengths were tunable by 1 nm by changing the crystal temperature by 20 °C. The continuous tuning of the beat frequency between the signal and the idler was achieved by temperature tuning (slow control, 80 MHz/K) and E-field tuning (fast control, 0.75 MHz/V). We demonstrated the feasibility of frequency control by phase locking the beat frequency. The beat frequency could be successfully phase locked to a signal generated by a synthesizer through the electrooptic effect of the crystal. The phase locking could be maintained over 1 h. Received: 27 January 1998/Revised version: 9 March 1998     

A reliable profiled lightly doped drain (PLD) cell for high-densitysubmicrometer EPROM's and flash EEPROM's

A cell with a profiled lightly doped drain (PLD) structure is proposed for realizing high-density nonvolatile memories in the submicrometer range. The PLD cell has a surface n^- layer with a diffusion self-aligned (DSA) boron layer, in addition to a deep phosphorus n^- layer. This structure enhances hot-electron generation during write and significantly reduces it during read. The cell exhibits improved data retention as a result of reduced band-to-band tunneling leakage current. The optimized PLD cell combines improved soft-write immunity with high read current, and low gate-induced breakdown leakage with high-speed writing. Simulation results and measurements on a fabricated test structure confirm these characteristics     

X-ray study of c-axis parameters in disordered stage II Agχ TiS2

X-ray measurements have been performed on disordered Stage II Ag_χ TiS₂ crystals with χ = 0.18 and 0.19. The c-axis structure was determined using the 00.l reflections for 4 ?l? 29. A principal result is that the intercalation of Ag⁺ between S layers produces unequal TiS distances in the adjacent TiS₂. The charge transfer to the Ti layer produces an expanded TiS distance adjacent to the Ag layer. The TiS distance away from the Ag ions is accordingly contracted. This effective (indirect) repulsive interaction between Ag⁺ and Ti may provide a mechanism for staging in these materials by keeping the Ag layers as far apart as possible.