DOCSLIB.ORG

Proton Capture Reactions and Nuclear Structure Proton Capture Reactions and Nuclear Structure

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Proton Capture Reactions and Nuclear Structure Proton Capture Reactions and Nuclear Structure Proton capture reactions and nuclear structure Proton capture reactions and nuclear structure Protonvangstreacties en kernstructuur (met een samenvat ting in het Nederlands) PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Rijksuniversiteit te Utrecht, op gezag van de rector magnificus prof. dr. J.A. van Ginkel, volgens besluit van het College van Decanen in het openbaar te verdedigen op woensdag 18 oktober 1989 des namiddags te 12.45 uur door Sybren Wouter Kikstra geboren op 14 augustus 1962 te Almelo PROMOTOR: PROF. DR. C. VAN DER LEUN Dit werk is een onderdeel van het onderzoeksprogramma van de "Stichting voor Fundamenteel Onderzoek der Materie" (FOM), die financieel gesteund wordt door de "Nederlandse Organisatie voor Wetenschappelijk Onderzoek" (NWO). Adagio cuUbilr — Ludwig van Beethoven Contents 1 Introduction 9 1.1 Historical notes 9 1.2 Proton capture reactions 10 1.3 Resonant absorption 11 1.4 Summary 11 2 Resonant absorption by the lowest two T = 3/2 levels of 9Be 15 2.1 Introduction 15 2.2 Experimental 16 2.3 Measurements and data analysis 18 2.4 Results 20 2.5 Theory and discussion 22 2.5.1 The Ex = 14.393 MeV, J*;T = 3/2"; 3/2 level 24 2.5.2 The Ex = 16.975 MeV, J*;T = 1/2"; 3/2 level 25 3 Superallowed 42Sc(/?+)42Ca decay 31 3.1 Introduction 31 3.2 The 41Ca(n,7)42Ca measurements 32 3.3 The 41Ca(p,7)42Sc measurements 32 3.3.1 Experimental 32 42 3.3.2 Determination of 5p( Sc) 35 3.3.3 Levels of 42Sc 38 3.4 The 42Sc->42Ca superallowed ft value 41 4 Investigation of the 40Ca level scheme 51 4.1 Introduction 51 4.2 Experimental 52 39 4.3 The K+p resonances for Ep = 0.3-2.9 MeV 53 4.3.1 Measurements 53 4.3.2 Analysis 53 4.3.3 Results and discussion 60 Contents 4.4 Gamma-ray spectra 65 4.4.1 Measurements 65 4.4.2 Analysis 65 4.4.3 Results and discussion 70 4.5 Shell model calculations 81 4.5.1 Introduction 81 4.5.2 The WBMB interaction 83 4.5.3 Calculations 83 4.5.4 Results and discussion 85 4.6 Summary and conclusions 91 Statistical nuclear spin assignments 95 5.1 Introduction 95 5.2 Average spins 95 5.3 Weighted averages 99 5.4 Chi-squared tests 102 5.4.1 Resonances 102 5.4.2 Bound states 108 5.5 New assignments 109 5.6 Summary and conclusion 109 Appendix 113 Samenvatting 115 Nawoord 117 Curriculum vitae 119 Chapter 1 Introduction In this thesis experimental studies are described of the structure of some atomic nuclei. Where possible, an attempt has been made to interpret the results of the measurements in terms of existing models. The 40Ca and 42Sc nuclides were excited by bombarding 39K and 41Ca targets, respectively, with low energy protons (Ep = 0.3-3.0 MeV), that were produced by the Utrecht 3 MV Van de GraafF accelerator. From the measured energy and intensity of the 7-rays created in the subsequent decay of the nuclei, accurate information was obtained on the existence and properties of their excited states. The nuclear reactions of this type are referred to as proton-capture or (p,7) reactions. In addition, properties of two levels at high excitation energy of the 9Be nucleus were investigated. These levels were excited by the resonant absorption of 7-rays from the nB(p,7)12C reaction. The above, essentially independent investigations are described in chapters 2-5 of this thesis in the style presently required by the international physics journals, i.e. rather concisely. The purpose of the rest of this introduction is to provide the reader with some background information which may be considered 'common knowledge' in publications. We will start with some historical notes, proceed with a short discussion of the merits of capture reactions and resonant absorption in nuclear spectroscopy, and finally give some details specific to the above mentioned subjects of this thesis. 1.1 Historical notes The discovery by Pose [1] in 1929 of a resonant effect in the bombardment of a thin aluminum foil with a-particles from a radioactive source, marks the start of the exploitation of resonances in capture reactions for obtaining data on properties of nuclear energy levels. In 1935, resonances in the yield of a proton induced reaction were observed by Hafstadt and Tuve [2] who used a 10 Introduction Van de Graaff accelerator, and narrow (few keV) separated (p,7) resonances were first measured with a Geiger Miiller counter by Tangen [3] during world war II. Giant steps forward in the detection techniques were made around 1955, when the high efficiency Nal detectors became generally available, and again in 1966 with the introduction of high-resolution semiconductor detectors of the Ge(Li) type. Presently, Ge and Ge(Li) detectors are used, often surrounded by a scintillator which is effective in the reduction of the counting of unwanted background radiation [4,5]. Nal detectors are still in use when energy resolution is less important than efficiency [6]. The importance of the developments in computer facilities and data acquisition techniques hardly needs mentioning. 1.2 Proton capture reactions Proton capture resonance reactions are an excellent tool for nuclear structure investigations. Firstly, the reaction process is very well understood. Provided that the reaction proceeds through separated resonances, which is the case when the bombarding energy is not too high, the compound system has a well-defined angular momentum and the unquestioned single-level Breit-Wigner theory may be applied. Secondly, the electromagnetic interaction is the best understood of all four fundamental interactions; the results of electromagnetic theory and experiment agree on the 1 ppm level. The strength of the electromagnetic in- teraction is ideal; it is sufficiently large to cause easily observable effects of the charge and current distribution in the nucleus, and small enough, compared to the strong interaction, to validate the application of perturbation theory for the analysis of the observed effects. The above considerations imply that the results of the measurements are model-independent, and consequently the data may be treated statistically. The availability, in most cases, of a variety of resonances with different spins and parities favourably distinguishes the (p,7) reaction from e.g. thermal neu- tron capture. Specific bound states may thus be excited with different intensities at different (p,7) resonances, which is especially advantageous in the identifica- tion and disentanglement of close doublets [4]. It should be mentioned, however, that the (p,7) and (n,7) reactions are complementary in that there are no p- and sd-shell nuclei which can be studied in both reactions. Another advantage of (p,7) reactions is the possibility to measure the lifetimes of nuclear excited states from the observed Doppler shifts of the energies of 7-rays emitted by the recoiling final nucleus [4,5]. The power of (p,7) reactions in combination with a good detector system was beautifully demonstrated in the study by Endt et al. [7] of 26A1, which is now by far the best known nucleus in the sd-shell. The data are ideally suited Resonant absorption 11 for tests of chaos theory (see e.g. [8]), for which complete (no missing levels) and pure (correct spin assignments) data are of utmost importance. The availability of complete and pure information has prompted the study of a new method for the assignment of nuclear level spins, which is discussed in chapter 5 of this thesis. For further reading the reader is referred to refs. [9-11]. 1.3 Resonant absorption As was first shown in 1957 [12,13], it is feasible to use proton capture resonances as a source of tuneable monoenergetic 7-rays to excite nuclear levels. A 7- ray energy slightly higher than the excitation energy of the level is needed to compensate for the recoil energy losses at emission and absorption. The angle dependence of the Doppler shift provides the energy tuneability for obtaining a resonant dip in the transmission cross section, which contains the nuclear structure information. In the first experiments a level was 'self-excited' by the Doppler-shifted decay 7-rays of that same level. The feasibility of 'cross excitation' of a level in one nucleus by a 7-ray from another nucleus was first demonstrated by Sparks et al. [14]. The resonant absorption method is reviewed in ref. [15]. 1.4 Summary Chapter 2 describes an investigation of the lowest two T = 3/2 levels of 9Be. As shown schematically in fig. 1.1, these levels were excited by 7-rays arising from broad resonances in the nB(p,7)12C reaction. The results of the measurements are interpreted by a comparison to the analogue /?-decay of 9Li and to shell model calculations. The basic idea behind the experiments presented in chapter 3 is contained in the following equations + Trip = m42Sc + Sp, and thus Tl = ~ ' «ca Sn — Sp + mp — mn, where m denotes the mass in energy units, and 5n and Sp are the neutron separation energy in 42Ca and the proton separation energy in 42Sc, respectively. Fig. 1.2 illustrates the situation in the form of simplified level schemes. The total decay energy of the superallowed 0+ —• 0+ /?+ transition between the ground states of 42Sc and 42Ca was thus determined accurately by measure- 42 42 ments in Utrecht of Sp of Sc and in Oak Ridge of Sa of Ca. The results were 12 Introduction f,x(MeV) f,T £x (MeV) (MeV) 18.83 .
Load more

Recommended publications
  • Carbon Capture: a Technology Assessment
    Carbon Capture: A Technology Assessment Peter Folger, Coordinator Specialist in Energy and Natural Resources Policy November 5, 2013 Congressional Research Service 7-5700 www.crs.gov R41325 CRS Report for Congress Prepared for Members and Committees of Congress Carbon Capture: A Technology Assessment Summary Carbon capture and sequestration (or carbon capture and storage, CCS) is widely seen as a critical strategy for limiting atmospheric emissions of carbon dioxide (CO2)—the principal “greenhouse gas” linked to global climate change—from power plants and other large industrial sources. This report focuses on the first component of a CCS system, the CO2 capture process. Unlike the other two components of CCS, transportation and geologic storage, the CO2 capture component of CCS is heavily technology-dependent. For CCS to succeed at reducing CO2 emissions from a significant fraction of large sources in the United States, CO2 capture technologies would need to be deployed widely. Widespread commercial deployment would likely depend, in part, on the cost of the technology deployed to capture CO2. This report assesses prospects for improved, lower- cost technologies for each of the three current approaches to CO2 capture: post-combustion capture; pre-combustion capture; and oxy-combustion capture. While all three approaches are capable of high CO2 capture efficiencies (typically about 90%), the major drawbacks of current processes are their high cost and the large energy requirements for operation. Another drawback in terms of their availability for greenhouse gas mitigation is that at present, there are still no full-scale applications of CO2 capture on a coal-fired or gas-fired power plant (i.e., a scale of several hundred megawatts of plant capacity).
    [Show full text]
  • A Revisionist History of Regulatory Capture WILLIAM J
    This chapter will appear in: Preventing Regulatory Capture: Special Interest . Influence and How to Limit it. Edited by Daniel Carpenter and David Moss. Copyright © 2013 The Tobin Project. Reproduced with the permission of Cambridge University Press. Please note that the final chapter from the Cambridge University Press volume may differ slightly from this text. A Revisionist History of Regulatory Capture WILLIAM J. NOVAK A Revisionist History of Regulatory Capture WILLIAM J. NOVAK PROFESSOR, UNIVERSITY OF MICHIGAN SCHOOL OF LAW The idea of regulatory capture has controlled discussions of economic regulation and regulatory reform for more than two generations. Originating soon after World War II, the so-called “capture thesis” was an early harbinger of the more general critique of the American regulatory state that dominated the closing decades of the 20th century. The political ramifications of that broad critique of government continue to be felt today both in the resilient influence of neoliberal policies like deregulation and privatization as well as in the rise of more virulent and populist forms of anti-statism. Indeed, the capture thesis has so pervaded recent assessments of regulation that it has assumed something of the status of a ground norm – a taken-for-granted term of art and an all-purpose social-scientific explanation – that itself frequently escapes critical scrutiny or serious scholarly interrogation. This essay attempts to challenge this state of affairs by taking a critical look at the emergence of regulatory capture theory from the perspective of history. After introducing a brief account of the diverse intellectual roots of the capture idea, this essay makes three interpretive moves.
    [Show full text]
  • Fundamental Stellar Parameters Radiative Transfer Stellar
    Fundamental Stellar Parameters Radiative Transfer Stellar Atmospheres Equations of Stellar Structure Nuclear Reactions in Stellar Interiors Binding Energy Coulomb Barrier Penetration Hydrogen Burning Reactions Burning of Helium and Heavier Elements Element Abundances Creation of Elements Heavier than Iron Introduction Stellar evolution is determined by the reactions which take place within stars: Binding energy per nucleon determines the most stable isotopes • and therefore the most probable end products of fusion and fis- sion reactions. For fusion to occur, quantum mechanical tunneling through the • repulsive Coulomb barrier must occur so that the strong nuclear force (which is a short-range force) can take over and hold the two nuclei together. Hydrogen is converted to helium by the PP-Chain and CNO- • Cycle. In due course, helium is converted to carbon and oxygen through • the 3α-reaction. Other processes, such as neutron capture reactions, produce heav- • ier elements. Binding Energy Per Nucleon { I The general description of a nuclear reaction is I(A , Z ) + J(A , Z ) K(A , Z ) + L(A , Z ) i i j j ↔ k k ` ` where A is the baryon number, nucleon number or nuclear mass of nucleus N and • n Z is the nuclear charge of nucleus N. • n The nucleus of any element (or isotope) N is uniquely defined by the two integers An and Zn. Note also that anti-particles have the opposite charge to their corresponding particle. In any nuclear reaction, the following must be conserved: the baryon number (protons, neutrons and their anti-particles), • the lepton number (electrons, positrons, neutrinos and anti-neutrinos) and • charge.
    [Show full text]
  • Redalyc.Projected Shell Model Description for Nuclear Isomers
    Revista Mexicana de Física ISSN: 0035-001X [email protected] Sociedad Mexicana de Física A.C. México Sun, Yang Projected shell model description for nuclear isomers Revista Mexicana de Física, vol. 54, núm. 3, diciembre, 2008, pp. 122-128 Sociedad Mexicana de Física A.C. Distrito Federal, México Available in: http://www.redalyc.org/articulo.oa?id=57016055020 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative REVISTA MEXICANA DE FISICA´ S 54 (3) 122–128 DICIEMBRE 2008 Projected shell model description for nuclear isomers Yang Sun Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, P.R. China, Joint Institute for Nuclear Astrophysics, University of Notre Dame, Notre Dame, Indiana 46545, USA. Recibido el 10 de marzo de 2008; aceptado el 7 de mayo de 2008 The study of nuclear isomer properties is a current research focus. To describe isomers, we present a method based on the Projected Shell Model. Two kinds of isomers, K-isomers and shape isomers, are discussed. For the K-isomer treatment, K-mixing is properly implemented in the model. It is found however that in order to describe the strong K-violation more efficiently, it may be necessary to further introduce triaxiality into the shell model basis. To treat shape isomers, a scheme is outlined which allows mixing those configurations belonging to different shapes. Keywords: Shell model; nuclear energy levels. Se estudian las propiedades de isomeros´ nucleares a traves´ del modelo de capas proyectadas.
    [Show full text]
  • Dispersion of Flies by Flight
    DISPERSION OF FLIES BY FLIGHT By F. C. BISHOPP, Entomologist, and E. W. I^AAKë, Entomological Assistant, Inves- tigations of Insects Affecting the Health of Man and Animals, Bureau of Entomology, United States Department of Agriculture A definite knowledge of the means of dissemination of various species of economic insects is of much importance in control or eradicative undertakings. Undoubtedly the spread of injurious forms by artificial means is in general of most pronounced importance. With free-fiying species, however, natural dispersion deserves careful consideration. This is particularly true of the various species of flies which directly affect man and animals. The accumulation of data on the possibilities of flight of various injurious species of flies should aid economic work in several ways. i. It should help in the study of the spread of fly-borne diseases, either in large districts or locally. 2. It should make possible the proper location of dumps, incinerators, hog-feeding stations, and other favorable breeding grounds so that the menace to towns, cities, military camps, etc., will be reduced to a minimum. 3. In control work in restricted districts or about individual plants it should help in determining the extent to which fly-breeding grounds in the neighborhood affect these undertakings. 4. In the prosecution of large-scale control work against certain species on farms or ranges, it should show how widespread must be the effort if marked results are to be accomplished. 5. It should make it possible to determine whether control campaigns are accumulative from year to year in their effect, or whether, owing to extensive migration, the results are effective only during one year or one period.
    [Show full text]
  • The Truth of the Capture of Adolf Eichmann (Pdf)
    6/28/2020 The Truth of the Capture of Adolf Eichmann » Mosaic THE TRUTH OF THE CAPTURE OF ADOLF EICHMANN https://mosaicmagazine.com/essay/history-ideas/2020/06/the-truth-of-the-capture-of-adolf-eichmann/ Sixty years ago, the infamous Nazi official was abducted in Argentina and brought to Israel. What really happened, what did Hollywood make up, and why? June 1, 2020 | Martin Kramer About the author: Martin Kramer teaches Middle Eastern history and served as founding president at Shalem College in Jerusalem, and is the Koret distinguished fellow at the Washington Institute for Near East Policy. Listen to this essay: Adolf Eichmann’s Argentinian ID, under the alias Ricardo Klement, found on him the night of his abduction. Yad Vashem. THE MOSAIC MONTHLY ESSAY • EPISODE 2 June: The Truth of the Capture of Adolf Eichmann 1x 00:00|60:58 Sixty years ago last month, on the evening of May 23, 1960, the Israeli prime minister David Ben-Gurion made a brief but dramatic announcement to a hastily-summoned session of the Knesset in Jerusalem: A short time ago, Israeli security services found one of the greatest of the Nazi war criminals, Adolf Eichmann, who was responsible, together with the Nazi leaders, for what they called “the final solution” of the Jewish question, that is, the extermination of six million of the Jews of Europe. Eichmann is already under arrest in Israel and will shortly be placed on trial in Israel under the terms of the law for the trial of Nazis and their collaborators. In the cabinet meeting immediately preceding this announcement, Ben-Gurion’s ministers had expressed their astonishment and curiosity.
    [Show full text]
  • GORILLA Report on the Conservation Status of Gorillas
    Version CMS Technical Series Publication N°17 GORILLA Report on the conservation status of Gorillas. Concerted Action and CMS Gorilla Agreement in collaboration with the Great Apes Survival Project-GRASP Royal Belgian Institute of Natural Sciences 2008 Copyright : Adrian Warren – Last Refuge.UK 1 2 Published by UNEP/CMS Secretariat, Bonn, Germany. Recommended citation: Entire document: Gorilla. Report on the conservation status of Gorillas. R.C. Beudels -Jamar, R-M. Lafontaine, P. Devillers, I. Redmond, C. Devos et M-O. Beudels. CMS Gorilla Concerted Action. CMS Technical Series Publication N°17, 2008. UNEP/CMS Secretariat, Bonn, Germany. © UNEP/CMS, 2008 (copyright of individual contributions remains with the authors). Reproduction of this publication for educational and other non-commercial purposes is authorized without permission from the copyright holder, provided the source is cited and the copyright holder receives a copy of the reproduced material. Reproduction of the text for resale or other commercial purposes, or of the cover photograph, is prohibited without prior permission of the copyright holder. The views expressed in this publication are those of the authors and do not necessarily reflect the views or policies of UNEP/CMS, nor are they an official record. The designation of geographical entities in this publication, and the presentation of the material, do not imply the expression of any opinion whatsoever on the part of UNEP/CMS concerning the legal status of any country, territory or area, or of its authorities, nor concerning the delimitation of its frontiers and boundaries. Copies of this publication are available from the UNEP/CMS Secretariat, United Nations Premises.
    [Show full text]
  • The FRIB Decay Station
    The FRIB Decay Station WHITEPAPER The FRIB Decay Station This document was prepared with input from the FRIB Decay Station Working Group, Low-Energy Community Meetings, and associated community workshops. The first workshop was held at JINPA, Oak Ridge National Laboratory (January 2016) and the second at the National Superconducting Cyclotron Laboratory (January 2018). Additional focused workshops were held on γ-ray detection for fast beams at Argonne National Laboratory (November 2017) and stopped beams at Lawrence Livermore National Laboratory (June 2018). Contributors and Workshop Participants (24 institutions, 66 individuals) Mitch Allmond Miguel Madurga Kwame Appiah Scott Marley Greg Bollen Zach Meisel Nathan Brewer Santiago MunoZ VeleZ Mike Carpenter Oscar Naviliat-Cuncic Katherine Childers Neerajan Nepal Partha Chowdhury Shumpei Noji Heather Crawford Thomas Papenbrock Ben Crider Stan Paulauskas AleX Dombos David Radford Darryl Dowling Mustafa Rajabali Alfredo Estrade Charlie Rasco Aleksandra Fijalkowska Andrea Richard Alejandro Garcia Andrew Rogers Adam Garnsworthy KrZysZtof RykacZewski Jacklyn Gates Guy Savard Shintaro Go Hendrik SchatZ Ken Gregorich Nicholas Scielzo Carl Gross DariusZ Seweryniak Robert GrzywacZ Karl Smith Daryl Harley Mallory Smith Morten Hjorth-Jensen Artemis Spyrou Robert Janssens Dan Stracener Marek Karny Rebecca Surman Thomas King Sam Tabor Kay Kolos Vandana Tripathi Filip Kondev Robert Varner Kyle Leach Kailong Wang Rebecca Lewis Jeff Winger Sean Liddick John Wood Yuan Liu Chris Wrede Zhong Liu Rin Yokoyama Stephanie Lyons Ed Zganjar “Close collaborations between universities and national laboratories allow nuclear science to reap the benefits of large investments while training the next generation of nuclear scientists to meet societal needs.” – [NSAC15] 2 Table of Contents EXECUTIVE SUMMARY ........................................................................................................................................................................................
    [Show full text]
  • Technical Summary 17
    Technical Summary 17 IPCC Special Report Carbon Dioxide Capture and Storage Technical Summary Coordinating Lead Authors Edward Rubin (United States), Leo Meyer (Netherlands), Heleen de Coninck (Netherlands) Lead Authors Juan Carlos Abanades (Spain), Makoto Akai (Japan), Sally Benson (United States), Ken Caldeira (United States), Peter Cook (Australia), Ogunlade Davidson (Sierra Leone), Richard Doctor (United States), James Dooley (United States), Paul Freund (United Kingdom), John Gale (United Kingdom), Wolfgang Heidug (Germany), Howard Herzog (United States), David Keith (Canada), Marco Mazzotti (Italy and Switzerland), Bert Metz (Netherlands), Balgis Osman-Elasha (Sudan), Andrew Palmer (United Kingdom), Riitta Pipatti (Finland), Koen Smekens (Belgium), Mohammad Soltanieh (Iran), Kelly (Kailai) Thambimuthu (Australia and Canada), Bob van der Zwaan (Netherlands) Review Editor Ismail El Gizouli (Sudan) 18 Technical Summary Contents 1. Introduction and framework of this report ...........................................................................................................................19 2. Sources of CO2 . .....................................................................................................................................................................22 3. Capture of CO2 .................................................................................................................................................................. ....24 4. Transport of CO2 ...............................................................................................................................................................
    [Show full text]
  • The Cognitive Locus of Distraction by Acoustic Novelty in the Cross-Modal Oddball Task
    ARTICLE IN PRESS Cognition xxx (2007) xxx–xxx www.elsevier.com/locate/COGNIT The cognitive locus of distraction by acoustic novelty in the cross-modal oddball task Fabrice B.R. Parmentier a,b,*, Gregory Elford a, Carles Escera c, Pilar Andre´s a, Iria San Miguel c a School of Psychology, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK b School of Psychology, University of Western Australia, Australia c Cognitive Neuroscience Research Group, Department of Psychiatry and Clinical Psychobiology, University of Barcelona, Catalonia, Spain Received 24 July 2006; revised 11 March 2007; accepted 11 March 2007 Abstract Unexpected stimuli are often able to distract us away from a task at hand. The present study seeks to explore some of the mechanisms underpinning this phenomenon. Studies of involun- tary attention capture using the oddball task have repeatedly shown that infrequent auditory changes in a series of otherwise repeating sounds trigger an automatic response to the novel or deviant stimulus. This attention capture has been shown to disrupt participants’ behavioral performance in a primary task, even when distractors and targets are asynchronous and pre- sented in distinct sensory modalities. This distraction effect is generally considered as a by-prod- uct of the capture of attention by the novel or deviant stimulus, but the exact cognitive locus of this effect and the interplay between attention capture and target processing has remained rel- atively ignored. The present study reports three behavioral experiments using a cross-modal oddball task to examine whether the distraction triggered by auditory novelty affects the pro- cessing of the target stimuli.
    [Show full text]
  • STUDY of the NEUTRON and PROTON CAPTURE REACTIONS 10,11B(N, ), 11B(P, ), 14C(P, ), and 15N(P, ) at THERMAL and ASTROPHYSICAL ENERGIES
    STUDY OF THE NEUTRON AND PROTON CAPTURE REACTIONS 10,11B(n, ), 11B(p, ), 14C(p, ), AND 15N(p, ) AT THERMAL AND ASTROPHYSICAL ENERGIES SERGEY DUBOVICHENKO*,†, ALBERT DZHAZAIROV-KAKHRAMANOV*,† *V. G. Fessenkov Astrophysical Institute “NCSRT” NSA RK, 050020, Observatory 23, Kamenskoe plato, Almaty, Kazakhstan †Institute of Nuclear Physics CAE MINT RK, 050032, str. Ibragimova 1, Almaty, Kazakhstan *[email protected] †[email protected] We have studied the neutron-capture reactions 10,11B(n, ) and the role of the 11B(n, ) reaction in seeding r-process nucleosynthesis. The possibility of the description of the available experimental data for cross sections of the neutron capture reaction on 10B at thermal and astrophysical energies, taking into account the resonance at 475 keV, was considered within the framework of the modified potential cluster model (MPCM) with forbidden states and accounting for the resonance behavior of the scattering phase shifts. In the framework of the same model the possibility of describing the available experimental data for the total cross sections of the neutron radiative capture on 11B at thermal and astrophysical energies were considered with taking into account the 21 and 430 keV resonances. Description of the available experimental data on the total cross sections and astrophysical S-factor of the radiative proton capture on 11B to the ground state of 12C was treated at astrophysical energies. The possibility of description of the experimental data for the astrophysical S-factor of the radiative proton capture on 14C to the ground state of 15N at astrophysical energies, and the radiative proton capture on 15N at the energies from 50 to 1500 keV was considered in the framework of the MPCM with the classification of the orbital states according to Young tableaux.
    [Show full text]
  • Photofission Cross Sections of 232Th and 236U from Threshold to 8
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1972 Photofission cross sections of 232Th nda 236U from threshold to 8 MeV Michael Vincent Yester Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Nuclear Commons Recommended Citation Yester, Michael Vincent, "Photofission cross sections of 232Th nda 236U from threshold to 8 MeV " (1972). Retrospective Theses and Dissertations. 6137. https://lib.dr.iastate.edu/rtd/6137 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This dissertation was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1. The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round black mark, it is an indication that the photographer suspected that the copy may have moved during exposure and thus cause a blurred image.
    [Show full text]