Description: This article discusses charge-state dependence of M-shell x-ray production in 67Ho by 2-12-MeV carbon ions. Abstract: Charge-state dependence of M-shell x-ray production cross sections of 67Ho bombarded by 2-12-MeV carbon ions, with and without K-shell vacancies, were measured using a windowless Si(Li) x-ray detector with a full-width-at-half-maximum resolution of 135 eV at 5.9 keV. Carbon ions of different charge states were produced using a postacceleration, nitrogen gas stripping cell. The carbon ions were then magnetically analyzed to select the desired charge state and energy before entering the target chamber. The total M-shell and Mζ, Mα,β, and Mγ x-ray cross sections were measured. The electron-capture (EC) contributions as well as the direct-ionization (DI) contributions can be determined by making a comprehensive study of the projectile-charge-state dependence of the target x-ray production cross sections for targets in which the single-collision realm is maintained. In this paper, both EC and DI contributions and the total M-shell x-ray production cross sections are compared to both the first Born theory and to the perturbed-stationary-state theory with energy-loss, Coulomb-deflection, and relativistic corrections.

Description: This article discusses the control of chaos in a CO2 laser. Abstract: We report the experimental control of chaos in an optically modulated CO2 laser. The CO2 laser was driven into chaos by injecting a feedback beam modulated by an electro-optical modulator. Control of chaos was achieved using a modified proportional feedback technique in which the control pulses were delayed by approximately one relaxation period. Using this technique, it was possible to control unstable periodic orbits up to period 6.

Description: This article discusses direct evidence for the amorphous silicon phase in visible photoluminescent porous silicon. Abstract: We report on micro-Raman spectroscopy studies of porous silicon which show an amorphous silicon Raman line at 480 R cm-1 from regions that emit visible photoluminescence. A Raman line corresponding to microcrystalline silicon at 510 R cm-1 is also observed. X-ray photoelectron spectroscopy data is presented which shows a high silicon-dioxide content in porous silicon consistent with an amorphous silicon phase.

Description: This article discusses a dynamical approach to Lévy processes.Abstract: We derive the diffusion process generated by a correlated dichotomous fluctuating variable y starting from a Liouville-like equation by means of a projection procedure. This approach makes it possible to derive all statistical properties of the diffusion process from the correlation function of the dichotomous fluctuating variable Φy(t). Of special interest is that the distribution of the times of sojourn in the two states of the fluctuating process is proportional to d²Φy(t)/dt². Furthermore, in the special case where Φy(t) has an inverse power law, with the index β ranging from 0 to 1, thus making it nonintegrable, the authors show analytically that the statistics of the diffusing variable approximate in the long-time limit the α-stable Lévy distributions. The departure of the diffusion process of dynamical origin from the ideal condition of the Lévy statistics is established by means of a simple analytical expression. We note, first of all, that the characteristic function of a genuine Lévy process should be an exponential in time. We evaluate the correction to this exponential and show it to be expressed by a harmonic time oscillation modulated by the correlation function Φy(t). Since the characteristic function ...

Description: This article discusses an effective core potential study of transition-metal chalcogenides. Abstract: A structural analysis is reported of roughly 150 transition-metal (TM)-chalcogenido complexes in a variety of chemical environments. With few exceptions, agreement between calculated and experimental geometries is excellent. The research provides convincing evidence that computational methods employed are adequately describing the bonding in these diverse TM complexes. Interesting trends in relative TMCh (Rмсh-Rмсh) bond lengths are found. Experimental and computational data show that other than the zirconocene-and halfnocene-oxos there is similar behavior in relative bond lengths for widely varying TM-chalcogenido complexes. Relative bond lengths versus oxo (S-O, Se-O, and Te-O) in group IVB metallocenes tend to be larger than for other families of complexes and show less variation among the heavier chalcogens (Se-S, Te-S, and Te-Se). Analysis of localized wave functions for Cp₂ZrCh point to a greater contribution from a singly-bonded Zr-Ch structure (relative to Zr=Ch) when Ch is O compared to heavier chalcogens. Taken together, the data suggest that there is a fundamental difference in the Zr-oxo (and Hf-oxo) bond in relation to heavier chalcogens, consistent with recent experimental data. In previous studies of multiply bonded TM complexes the authors have focused on the ability of ECPs ...