ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data

http://nrv.jinr.ru/nrv/webnrv/elastic_scattering/KoningP.pdf

Local and global nucleon optical models from 1 keV to 200 MeV

Nuclear Data Sheets for A = 152

We calculate the back-reaction of long wavelength cosmological perturbations on a general relativistic measure of the local expansion rate of the universe. Specifically, we consider a cosmological model in which matter is described by two scalar matter fields, one being the inflaton and the other one representing a matter field which is used as a clock. We analyse back-reaction in a phase of inflaton-driven slow-roll inflation, and find that the leading infrared back-reaction terms contributing to the evolution of the expansion rate do not vanish when measured at a fixed value of the clock field. We also analyse the back-reaction of entropy modes in a specific cosmological model with negative square mass for the entropy field and find that back-reaction can become significant. Our work provides evidence that, in general, the back-reaction of infrared fluctuations could be locally observable.

http://iopscience.iop.org/article/10.1088/1475-7516/2005/04/006/pdf

Back reaction of perturbations in two scalar field inflationary models

Nuclear data sheets for A = 194

Nuclear deformation of the $s\ensuremath{-}d$ shell nuclei $^{24}\mathrm{Mg}$, $^{28}\mathrm{Si}$, and $^{32}\mathrm{S}$ has been investigated by means of fast neutron scattering. Differential cross sections have been measured at the incident neutron energies of 9.76 and 14.83 MeV, over the angular range from 15\ifmmode^\circ\else\textdegree\fi{} to 160\ifmmode^\circ\else\textdegree\fi{}. Angular distributions have been obtained for the elastic scattering and the inelastic scattering to low lying collective states. The measurements have been compared to the predictions of collective models, and nuclear deformations have been determined for these nuclei. The coupled-channel and compound-nucleus formalisms were used in the calculations. The analysis shows that these nuclei exhibit quite different shapes, and confirms the oblate deformation of $^{28}\mathrm{Si}$ established in recent works. A detailed comparison of the deformations obtained in this study with those deduced from (p,p\ensuremath{'}), (d,d\ensuremath{'}), ($\ensuremath{\alpha}$,${\ensuremath{\alpha}}^{\ensuremath{'}}$), ($^{16}\mathrm{O}$, $^{16}\mathrm{O}\ensuremath{'}$), other (n,n\ensuremath{'}), and charge distribution measurements is presented and discussed. It is emphasized that for these $N=Z$ nuclei the quadrupole deformations and deformation lengths are in very good agreement when measured through neutron and proton scattering as well as electromagnetic excitations.

Nuclear deformations of /sup 24/Mg, /sup 28/Si, and /sup 32/S from fast neutron scattering

Differential cross sections for neutron scattering from four even-A isotopes of Sm have been measured at an incident energy of 7 MeV. Separated isotope samples having enrichments between 87.4 and 99.5% were used, each sample containing about 0.15 moles. Measurements have been separated for elastic and inelastic scattering to the first 2/sup +/ levels of /sup 148/Sm, /sup 150/Sm, and /sup 152/Sm. For /sup 154/Sm the two processes were not separated. The data show directly the striking effects of the difference in coupling between the 0/sup +/ and 2/sup +/ levels of these transitional nuclei. Accurately measured total cross sections and low energy scattering properties have been combined with these 7 MeV results in a coupled-channel analysis. Coupling parameters extracted from the analysis have been shown to be significantly less than the deformation parameters which characterize the charge distributions of the deformed isotopes.

Deformation effects in neutron scattering from the Sm isotopes

Neutron total cross sections of /sup 144/Nd and /sup 148/Sm and total cross-section differences for the pairs of isotopes /sup 144,142/Nd, /sup 146,144/Nd, /sup 148,144/Nd, /sup 150,144/Nd, /sup 150,148/Sm, /sup 152,148/Sm, and /sup 154,148/Sm have been measured at 25 energies from 0.75 to 14 MeV. Each sample consisted of about 40 g of powdered oxide with an isotopic enrichment >94%. For each isotopic pair the total cross-section difference was determined directly by measuring the ratio of transmitted flux for matched samples. This difference was found to have an oscillatory behavior when plotted as a function of incident neutron energy. The oscillations have been explained as a deformation effect qualitatively in terms of the nuclear Ramsauer effect and quantitatively using a deformed optical model potential. Adding two neutrons to a nucleus in this mass region was found to have a different effect on the neutron total cross section than adding two protons. A coupled channel analysis was performed using as input data the present total cross sections, low-energy neutron scattering parameters, and elastic and inelastic (2/sup +/) differential cross sections for neutron scattering at 4 and 7 MeV. Excellent total cross-section fits were obtained for the Sm isotopes; however, the totalmore » cross-section fits for the Nd isotopes were only fair. Quadrupole deformation parameters have been deduced for all the isotopes studied. The sensitivity of neutron total cross-section differences to this parameter and to the real isospin term of the nuclear potential is discussed.« less

Effects of deformation on neutron total cross sections of even-A Nd and Sm isotopes

Neutron scattering differential cross sections were measured for $^{232}\mathrm{Th}$, $^{238}\mathrm{U}$, and $^{239}\mathrm{Pu}$ at 14.1 MeV. Optical model calculations were performed using the coupled-channel formalism for deformed nuclei as given by Tamura. Several microscopic and phenomenological optical model potentials were tested for these heavy nuclei: (i) a folding optical model potential using the microscopic nucleon-nucleon effective interaction of Jeukenne, Lejeune, and Mahaux with deformed nuclear density distributions (these calculations are addressed in the text as semimicroscopic optical model potentials), (ii) global phenomenological optical model potentials optimized for the actinide region, and (iii) neutron potentials derived from 35 MeV proton optical potentials using the Lane formalism. The total cross sections calculated from these optical model potentials at 14.1 MeV are also compared with measurements in the literature. The semimicroscopic calculations reproduce reasonably well the measured angular distributions with only two free parameters used to optimize fits to the data. The calculations carried out with optical potentials inferred from proton data give good agreement with the neutron data, an agreement which is similar to that between calculational results using neutron global potentials optimized for this mass region and the measured data.

Measurements and calculations of neutron scattering in the actinide region.

Deformation effects in differential cross sections for neutron scattering from /sup 142,144,146,148,150/Nd have been studied at an incident energy of 7 MeV, where measurements and calculations of total cross sections show maximum differences for different deformations. Differential cross sections were obtained for elastic scattering and inelastic scattering to the first 2/sup +/ states of the five isotopes. The experimental cross sections are compared to the predictions of surface excitation models using coupled-channels calculations. The parameters of the model are adjusted to fit low energy scattering properties and total cross sections for incident energies from 0.7 to 14 MeV as well as the present data. The large set of data tightly constrains all parameters, including the quadrupole deformation parameters. These are compared to those obtained using other probes of the nuclear surface.

Optical potential and nuclear deformation for even Nd isotopes from fast neutron scattering

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Ch. Lagrange

Author Tools

Chat about Author