Demonstration of a transient-gain nickel-like xenon-ion x-ray laser

We demonstrate a high-gain nickel-like xenon-ion x-ray laser, using a picosecond-laser-irradiated gas-puff target. The elongated x-ray laser plasma column was produced by irradiation of the gas-puff target with line-focused double picosecond laser pulses with a total energy of 18 J in a traveling-wave excitation scheme. Strong lasing at 9.98 nm was observed, and a high gain coefficient of 17.4 cm(-1) was measured on the transient collisionally excited 4d-4p , J=0-1 transition for nickel-like xenon ions with target lengths as great as 0.45 cm. A weak nickel-like lasing line at a shorter wavelength of 9.64 nm was also observed, with a gain coefficient of 5.9 cm(-1) .     

Hole mobility enhancement in GaAs/p-Al Ga As QW-HEMT structures with (4 1 1)A super-flat interfaces grown by MBE

Be-doped GaAs/p-Al Ga As QW-HEMT structures with well width of and 50 nm were simultaneously grown on (4 1 1)A and (1 0 0) GaAs substrates by MBE. Be-doping concentration in the p-Al Ga As layer was , and the undoped Al Ga As spacer layer was 6 nm thick. Hole concentration was about for nm. Hole mobility at 10 K in the conventional (1 0 0) samples remained almost constant (about 20 000 cm (V s) for the current in the direction) with decreasing down to 7 nm and it rapidly decreased to 2760 cm (V s) at nm. On the other hand, in the (4 1 1)A samples, hole mobility (10 K) increased from 17 500 cm (V s) nm) to 33 900 cm (V s) nm) and dropped rapidly down to 4090 cm (V s) nm) for a current direction of . This significant enhancement of hole mobility in the (4 1 1)A samples is mainly due to (1) the significantly reduced interface roughness scattering of 2DHG when using the (4 1 1)A super-flat interfaces and (2) the reduced effective mass of holes in the narrow (4 1 1)A QWs ( –20 nm). Shubnikov–de Haas (SdH) measurements on the (4 1 1)A QW sample nm) confirmed the reduced effective mass (0.30 ) of holes.     

Theoretical calculation of the reduced viscosity of aqueous suspensions of charged spherical particles

The origin of the variety of characteristics of the reduced viscosity of aqueous suspensions of charged spherical particles has been an unsolved problem. To solve the problem, the reduced viscosity due to interparticle electrostatic interactions between charged spherical particles are calculated as a function of particle concentration with scanning various parameters, such as diameter of particle, number of charges per particle, and added‐salt concentration. The result successfully reproduced the variety of characteristics. Of all the scanned parameters, the diameter of the particle has a significant role to display the variety of characteristics when other parameters are fixed. When the diameter is very small (～0 Å), the calculated reduced viscosity of aqueous suspensions of charged spherical particles increases with decreasing particle concentration and it shows a maximum. This behavior is very similar to the reduced viscosity of linear chain polyelectrolyte solutions. Whereas, when the diameter is large (>2000 Å), the calculated reduced viscosity decreases with decreasing particle concentration and it does not show a maximum. When the diameter is <1000 Å, the calculated reduced viscosity shows both the maximum and minimum. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1068–1074, 2004     

Synthesis of benzo-fused lactams and lactones via Ru(II)-catalyzed cycloaddition of amide- and ester-tethered alpha,omega-diynes with terminal alkynes: electronic directing effect of internal conjugated carbonyl group

In the presence of a catalytic amount of Cp*RuCl(cod), 1,6- and 1,7-diynes connected by an amide or an ester tether underwent cycloaddition with terminal alkynes at room temperature to give rise to cycloadducts in 40-93% yields with 63 : 37-83 : 17 regioisomer ratios.     

Maximum Distance Codes in Mat n,s (Zk) with a Non-Hamming Metric and Uniform Distributions

We establish a bound on the minimum distance for codes in Mat _n,s (Z_k) with respect to their ranks and call codes meeting this bound MDR codes. We extend the relationship between codes in Mat _n,s (Z_k) and distributions in the unit cube and use the Chinese Remainder Theorem to construct codes and distributions.     

Opacity effect on extreme ultraviolet radiation from laser-produced tin plasmas

Opacity effects on extreme ultraviolet (EUV) emission from laser-produced tin (Sn) plasma have been experimentally investigated. An absorption spectrum of a uniform Sn plasma generated by thermal x rays has been measured in the EUV range (9-19 nm wavelength) for the first time. Experimental results indicate that control of the optical depth of the laser-produced Sn plasma is essential for obtaining high conversion to 13.5 nm-wavelength EUV radiation; 1.8% of the conversion efficiency was attained with the use of 2.2 ns laser pulses.     

Effect of savitzky—golay smoothing on second-derivative spectra

The rounding error arising from analog/digital conversion (12-bit) of a spectrum introduces small shoulders on the zero-order spectrum, which are enhanced in the second-derivative spectrum. To reduce this noise, Savitzky-Golay smoothing of the zero-order spectrum was examined by simulation. This smoothing procedure brings the second-derivative spectrum closer to the true spectrum. The effects of smoothing on the ultraviolet spectrum of salicylic acid in ethanolic solution are reported.