Search

In this work, total excitation cross section of atomic hydrogen in the collision of bare ion was calculated employing a three body Faddeev formalism. In the present calculation, initially the first order electronic amplitude was calculated using the interaction potential which led to inelastic form factor. Secondly, the first order nuclear amplitude was calculated and added to the first order electronic amplitude. This second term was calculated employing the near-the-shell two body transition operator. The interaction energy was assumed to be in the intermediate and high energy limits . Finally, the results were compared with the relevant cross sections calculated under monocentric close-coupling data in the literature.

Abstract A quantum theory is established for the propagation of electromagnetic waves in highly nonlinear dispersive optical fibers. By applying the method recently presented dispersion terms and retarded response of the medium are included for the propagation of light in a fiber in this work. A coupled stochastic generalized nonlinear Schrödinger equation (GNLSE) is obtained via the coherent positive-P representation to describe the supercontinuum generation process. This coupled quantum-stochastic equation is applied to obtain the linearized fluctuation equation for studying quantum noise and the fluctuation in the vicinity of the formed solitons in the supercontinuum generation process in the region of anomalous dispersion. Also, these equations can be used to study the soliton self-frequency shift quantum mechanically. Finally, we simulate the obtained coupled stochastic generalized nonlinear Schrödinger in the mean case and compare our simulation results with experimental results.

We have initiated a study to extract concentration profiles of ultra shallow phosphorous implants in silicon complementing published work on ultra shallow boron implant profiles. There is an ever-increasing interest in the production of p-n junctions in silicon to create the new generations of ultra large scale integrated (ULSI) devices. Such junctions can be formed by implantation do pants (such as B, P, and As) at lowered energies. Development of design tools and process implementation both require that accurate methods be available for confirming absolute do pant profiles. Traditionally, profiles have been extracted through the use of secondary ion mass spectroscopy (SIMS), Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA) and electrical measurements such as spreading resistance profilometry. Results of ion implanted species can be checked by SIMS (J.G.M. van Berkum, et al Vac. Sci. Technol. B16 (1998) 298). However, the analysis of ultra shallow implants by standard SIMS techniques is not straightforward and is weak in quantitative measurements. There are several reasons for this. First, standard methods of SIMS are hampered by limits on the instrumental sensitivity, which may not be adequate to examine very low-dose implants. Second, the accuracy in quantifying standard SIMS at very shallow depth is limited, due to an initial transitional region within which the sample composition equilibrates with the primary ion beam. This initial equilibration is characteristic of the SIMS technique, and is highly reproducible. Considerable effort has been expended in understanding the details of the equilibrium process, nevertheless, it is complicated even in the simplest of situations and continues to present problems for accurate quantification. Third, in specific situations high mass resolution required to separate the species of interest, or its proxy, from other mass groups, including impurity groups. Although there has been many investigations to extract quantitative profiles by SIMS using relative sensitivity factors (RSF), they can be reproduced 20-30% under more controlled conditions (R.G. Wilson, S.W. Novak, J. Appl. Phys. 69 (1991) 466). However, there is a need for other methods to normalize SIMS results. RBS is a candidate to calibrate SIMS profiles, but lacks the sensitivity to detect phosphorous due to the proximity of its mass with the masses of Si isotopes. Nuclear reaction analysis (NRA), 31P( a ,p)34S, is a suitable method for phosphorous detection. This nuclear reaction displays a resonance in the cross section at an incident energy near 5 MeV. While the cross section for the 31P( a ,p)34S reaction is small, we are able to measure the absolute do pant concentration of phosphorous implants into Si down to fluences of 1 ´ 1014cm-2. This opens a route to the calibration of TOF SIMS integrated profiles for P, which may then be used for analysis of the lower fluence regime. Two sets of phosphorous implanted silicon wafers were prepared. Phosphorous doses in our samples ranged from 1 ´ 1013 cm-2 to 5 ´ 1015 cm-2 with the implanted energy of 1 keV to 30 keV. To date, no evidence was found for self-sputtering based on these samples. The alpha capture reaction on phosphorous has been investigated in the field of nuclear physics to find the nuclear energy level of different isotopes. This reaction has been used in profiling P in silicon, but none to P concentrations and P implanted energies as low as those reported here. The present studies complement the work done on ultra shallow boron implant (Aditya Agarwal, et al Appl. Phys. Lett. 74 (1999) 2453).

In this report, we present a quantum theory describing the propagation of the electromagnetic radiation in a fiber in the presence of the third order dispersion coefficient. We obtained the quantum photon-polariton field, hence, we provide herein a coupled set of operator forms for the corresponding nonlinear Schrödinger equations when the third order dispersion coefficient is included. Coupled stochastic nonlinear Schrödinger equations were obtained by applying a positive P-representation that governs the propagation and interaction of quantum solitons in the presence of the third-order dispersion term. Finally, to reduce the fluctuations near solitons in the first approximation, we developed coupled stochastic linear equations. [ABSTRACT FROM AUTHOR]

In this work, differential cross sections have been calculated for the excitation of atomic hydrogen (H) from its ground state (1s) into a selection of its excited states (2s, 2p0, 2p+-1 and 3s). The present study was conducted at intermediate and high proton impact energies within the range 50 keV-1 MeV. A three-body model based on Faddeev-type equations is implemented, while near the energy shell the two-body Coulomb transition matrix was used to calculate the transition amplitude. Second and higher order approximations have been ignored in this case. The resulting amplitudes are subsequently utilized to calculate total and differential cross sections for the corresponding excitation processes. These calculated cross sections have then been compared with available experimental data and other theoretical results from the literature. [ABSTRACT FROM AUTHOR]