Search results for "scattering [p nucleus]"
showing 10 items of 198 documents
Second-order approximations to laser-assisted charged-particle scattering.
1990
Multiphoton free-free transitions within a full second-order treatment of the scattering potential are considered with two specific aims: (i) to test some widely used approximations against exact calculations; (ii) to present differential cross sections for the laser-assisted positron scattering, in the regime of intermediate field intensities (up to ${10}^{13}$ W/${\mathrm{cm}}^{2}$). In the case of a field linearly polarized along the incident particle momentum, the results clearly discriminate among the approximations, setting interesting limitations to each of them as functions of the scattering potential features and of the field parameters. Each approach shows good performance for par…
Study of the Density and Temperature Dependences of the Vibrational Raman Transition in Compressed Liquid N2
1991
0021-9606; Accurate values of linewidth and line shift in the isotropic vibrational Raman spectrum of compressed liquid N2 have been obtained by using inverse Raman spectroscopy. Experiments have been performed for eight isotherms, from the normal boiling point to the critical point temperatures of N2, the number density varying between the value on the coexistence line, and the maximum value of 2.1 x 10^22 cm-3. Minima of the linewidth have been observed above 86 K, showing the increasing influence of vibration-rotation coupling (motional narrowing) competing with the broadening due to pure vibrational dephasing. Moreover, for the first time, maxima of the red line shifts have been found, …
Temperature Dependence of pHEMT-Based LNA Performance for VSAT Applications
1994
From a complete characterization in terms of noise and scattering parameters carried out at room temperature in the 8-16 GHz frequency range, the noisy small-signal model of a pseudomorphic HEMT series has been extracted. The transistor scattering parameters have been subsequently measured at lower temperatures (down to -50 °C) by placing the device text fixture in a thermo-controlled chamber. An accurate noisy model has then been extracted by determining the circuit element values at the different temperatures. The trade-off performance of a pHemt-based LNA for VSAT receiver system applications has been investigated vs. frequency and temperature.
Production of dark-matter bound states in the early universe by three-body recombination
2018
The small-scale structure problems of the universe can be solved by self-interacting dark matter that becomes strongly interacting at low energy. A particularly predictive model for the self-interactions is resonant short-range interactions with an S-wave scattering length that is much larger than the range. The velocity dependence of the cross section in such a model provides an excellent fit to self-interaction cross sections inferred from dark-matter halos of galaxies and clusters of galaxies if the dark-matter mass is about 19 GeV and the scattering length is about 17 fm. Such a model makes definite predictions for the few-body physics of weakly bound clusters of the dark-matter particl…
Ion beam analysis and alpha spectrometry of sources electrodeposited on several backings
1998
Abstract Alpha sources of several activities were prepared by electrodeposition of natural uranium onto four different backings: stainless steel, Ni, Mo and Ti. The influence of the activity, the type of backing, and the process of heating the source on the energy resolution of the spectra were investigated using alpha spectrometry and Rutherford Backscattering Spectrometry (RBS) techniques. Diffusion profiles of the radioactive deposits in the backings were obtained from RBS and related to the results using alpha spectrometry
Ion irradiation of AZO thin films for flexible electronics
2017
Aluminum doped Zinc oxide (AZO) is a promising transparent conductor for solar cells, displays and touch-screen technologies. The resistivity of AZO is typically improved by thermal annealing at temperatures not suitable for plastic substrates. Here we present a non-thermal route to improve the electrical and structural properties of AZO by irradiating the TCO films with O+ or Ar+ ion beams (30–350 keV, 3 × 1015–3 × 1016 ions/cm2) after the deposition on glass and flexible polyethylene naphthalate (PEN). X-ray diffraction, optical absorption, electrical measurements, Rutherford Backscattering Spectrometry and Atomic Force Microscopy evidenced an increase of the crystalline grain size and a …
Formation of cobalt silicide from filter metal vacuum arc deposited films
2006
The thermal reaction of Co film deposited on Si(111) surfaces by a high current filter metal vacuum arc (FMEVAD) system has been studied. After deposition the films were annealed over the 400-900 degrees C temperature range for 30 min. Rutherford backscattering spectrometry (RBS) was used to characterize the elemental depth distributions in the films subjected to different annealing temperatures. Ordered chemical phases were determined by glancing-incidence X-ray diffraction (GIXRD) and the morphology was determined by cross section transmission electron microscopy (TEM). The results show that the phases formed are Co2Si at 400 degrees C, CoSi + Coo at 500 degrees C, CoSi + CoSi2 at 600 deg…
A study of solar thermal absorber stack based on CrAlSiNx/CrAlSiNxOy structure by ion beams
2019
Renewable energies are foreseen as a major energy resource for next generations. Among several energy sources and technologies available, Concentrated Solar Power (CSP) technology has a great potential, but it needs to be optimised, in particular to reduce the costs, with an increase of the operating temperature and long term stability. This goal can be achieved by tailoring the composition and multilayer structure of films. In this work we present and discuss the results obtained from solar absorber coatings based on nitride/oxynitride structures. A four-layer film structure, W/CrAlSiNx(HA)/CrAlSiNxOy(LA)/SiAlOx, was deposited on stainless steel substrates using magnetron sputtering deposi…
Ordering effects in extreme high-resolution depth profiling with MeV ion beams
2012
Abstract The continuing development of depth profiling with MeV ion beam methods with depth resolutions in the nanometre, and even sub-nanometre, regime implies the resolved depth become comparable with the interatomic spacing. To investigate how short-range ordering influences depth profiles at these resolutions, we have employed a mathematical modelling approach. The radial, g ( r ) and depth distribution, g ( z ) functions were calculated for (1 0 0) surface, random and amorphous Si structures at 300 K produced using molecular dynamics simulations with the EDIP quasi-empirical potential. The results showed that short-range ordering lead to reduction of the scattering yield below the deep…
Characterization of alpha sources prepared by direct evaporation using Rutherford backscattering spectrometry
1997
Abstract Standardization of solutions containing alpha emitting nuclides by direct evaporation onto metal supports is a widely used technique due to its simplicity in providing good quantitative results. In order to avoid inhomogeneity in the deposition surface, polished stainless steel disks and a spreading agent are generally used. These sources are usually measured by alpha spectrometry using passivated implanted silicon detectors. The resolution of the source is a measure of the thickness and homogeneity of the evaporated layer. Rutherford backscattering of He+ and H+ was here used to measure directly this thickness and homogeneity. The results were in agreement with semiconductor detec…