Single mode operation was exhibited on the Israeli tandem free-electron laser (FEL). This enabled judicious measurements of narrow spectral linewidth, frequency chirp, and relaxation-oscillation effects. Exact 3D simulations of the FEL oscillator showed good agreement with the measurements, and permitted an estimation of the fundamental Schawlow-Towns linewidth limit of the FEL (including "a effect") as well as technical noise linewidth limits. We estimate that with voltage-controlled stabilization high-power (10 kW) tunable (over 60% bandwidth) quasi-cw coherent ͓͑Dn͞n͒ rms ഠ 10 210 ͔ mm-FIR (far infrared) radiation is attainable in the tandem FEL. [S0031-9007(99)09370-9]
We have measured the quantum detection efficiency (QDE) of potassium bromide as a photocathode applied directly to the surface of a microchannel plate over the 250-1600A wavelength range. The contributions of the photocathode material in the channels and on the interchannel web to the QDE have been determined. Two broad peaks in the QDE centered at ~450 and ~1050 A are apparent, the former with ~50% peak QDE and the latter with ~40% peak QDE. The photoelectric threshold is observed at ~1600 A, and there is a narrow QDE minimum at ~750 A which correlates with 2x the band gap energy for KBr. The angular variation of the QDE from 0 to 40 degrees to the channel axis has also been examined. The stability of KBr with time is shown to be good with no significant degradation of QDE at wavelengths below 1216 A over a 15-day period in air.
Heating of 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol (per-O-acetyl-D-glucal) in water leads to a mixture of unsaturated compounds with cyclic as well as open-chain structures. The mixture obtained was analyzed by the CGC method. The experimental findings were employed to model the mechanism of the transformation studied. In addition, AM1 calculations were carried out in order to describe the elementary processes suggested. Full geometry optimizations performed for species found in the mixture made it possible to evaluate the thermodynamic characteristics of particular reactions. Next, the calculations for transition states afforded appropriate kinetic barriers. All computations were carried out for a gaseous phase as well as an aqueous solution. Both experimental and theoretical results conform well with the mechanism proposed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.