Fifth Symposium on the Structure of Low-Medium Mass Nuclei

Fifth Symposium on the Structure of Low-Medium Mass Nuclei

J. P. DAVIDSON
BERNARD D. KERN
Copyright Date: 1973
Pages: 312
https://www.jstor.org/stable/j.ctt130j3tf
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  • Book Info
    Fifth Symposium on the Structure of Low-Medium Mass Nuclei
    Book Description:

    In this report of the proceedings of the Fifth Symposium prominent world physicists give an account of the status of the understanding of nuclear structure in the mass region from A=20 to A=60.

    Ten invited papers cover various aspects of nuclear structure from both the theoretical and the experimental points of view. Additionally, four short papers presenting formal comments are included, along with the edited discussions following the readings of the papers.

    Two topics are treated in particular: the long-awaited application of polarized beams to the study of nuclear structure is reviewed, with results from Stanford University; and a technique is described, that makes it possible for the first time to observe directly the decay of nuclear states.

    eISBN: 978-0-8131-6281-2
    Subjects: Physics

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. EDITORS' PREFACE
    (pp. vii-x)
  4. Session I Chairman:: P. Goldhammer
    • I.A. PROGRESS IN THE sd-SHELL
      (pp. 1-19)
      C. van der Leun

      Some twenty years ago, it was possible to summarize the spectroscopic information on sd-shell nuclei in one table of a few pages. That table listed all the known levels, including resonance levels.

      Today one has to apply all the tricks of condensation and of concise writing to be able to review our knowledge of the sd-shell nuclei in the scope of a book. Even then it is imperative to forget about all the data that have only historical significance, however interesting they may be. Moreover, one has to treat the practically infinite number of resonance levels in a stepmotherly fashion....

    • I.B. NEW APPLICATIONS OF HARTREE-FOCK CALCULATIONS TO NUCLEI WITH 20 < A < 60
      (pp. 20-50)
      H. C. Lee

      In the past decade or so the Hartree-Fock (HF) method has become increasingly popular as a tool for the study of nuclear physics. First it was used on calculations of the binding energy of nuclear matter and of finite nuclei as well. In time, these calculations have become more sophisticated in technique and more encompassing in aim. In recent years, one has become familiar with terminologies such as Brueckner-Hartree-Fock¹, deformed HF², HF-Bogoliubov³, density-dependent HF⁴, HF with three-body interactions⁵, and multi-configuration HF.⁶ All these are methods prescribed for specific but complementary improvements over the basic HF method, and it is a...

    • I.a. HIGH-SPIN STATES IN Al27 AND THE NUCLEAR STRUCTURE OF NUCLEI AROUND MASS 28
      (pp. 51-55)
      M. J. A. de Voigt

      Many attempts have been made to apply the collective model to nuclei in the mass region A = 27−29, where the nuclear shape changes from prolate to oblate. Several discussions of Al27in terms of rotational bands (see Reference 1) have been published, but they fail to explain many different features simultaneously. More experimental information, especially on high-spin states, might remove some of the existing ambiguities and uncertainties.

      Therefore levels in Al27have been investigated by means of the Na23(α,γ)Al27reaction, where the strongly competing proton emission turns out to provide a very useful natural selection mechanism in the observation...

    • I.b. THE RESOLUTION OF ANGULAR CORRELATION AMBIGUITIES FOR HIGH SPIN STATES USING A 3 Ge(Li) DETECTOR COMPTON POLARIMETER
      (pp. 56-62)
      J. F. Sharpey-Schafer

      Recent work¹ by P. J. Twin at Liverpool on the spin and mixing ratio ambiguities inherent in gamma ray angular correlation measurements shows that the most powerful method for resolving many of the ambiguities is to measure the linear polarization of the de-exciting gamma rays. The method is particularly successful for high spin states which decay by pure quadrupole radiation.

      At Liverpool a Compton polarimeter has been constructed consisting of three large (7 to 9% relative efficiency) Ge(Li) detectors with resolutions for 1.33 MeV photons between 2.0 and 3.0 keV. The largest detector is positioned in the horizontal plane at...

  5. Session II Chairman:: P. M. Endt
    • II.A. NUCLEAR STRUCTURE CALCULATIONS WITH REALISTIC TWO-BODY FORCES
      (pp. 63-89)
      S. Maripuu

      The promising results of the early work of Kuo and Brown1–4have inspired many studies of the use of realistic two-nucleon interactions in nuclear structure calculations. Realistic is used here to mean that the two-nucleon interaction is derived from the phase shift data from free nucleon-nucleon scattering. The two-nucleon interaction so derived is then transformed into an effective interaction to be used in a small model space. The successful results obtained by employing this method are many. A large number of physical quantities have been explained accurately, usually at least as well as is managed with empirical interactions (see...

    • II.B. ROLE OF NUCLEAR COEXISTENCE IN SHELL MODEL SPECTRAL DIFFERENCE CALCULATIONS
      (pp. 90-121)
      Philip Goode

      There are many examples of anomalous behavior of nuclei in the mass-40 region. It is the purpose of this paper to investigate some of these anomalies in terms of difference calculations. In the course of the investigation, it is also our purpose to illustrate the interplay of the valence effective interaction and space truncation as well as some convergence properties of the valence effective interaction and its effective particle rank.

      One of the oldest known anomalies in the mass-40 region is that of the Cl38/K40pair. Within the framework of the pure shell model, Cl38is a proton particle in...

    • II.a. ISOSCALAR MAGNETIC MOMENTS IN LIGHT NUCLEI
      (pp. 122-123)
      P. M. Endt

      The multicomponent wave functions provided by many particle shell model calculations can be used, amongst other things, to calculate magnetic dipole moments.

      In the course of such calculations for the sd-shell, van Hienen and Glaudemanslobserved that the g-factor for the isoscalar contribution to magnetic moments (in the following denoted by go) is remarkably constant. Almost all calculated go-values were found to lie in the 0.4-0.6 region, depending very little on the type of two body interaction employed or on the size of the shell model space. This is in contrast to the g-factor for the isovector contribution which was...

  6. Session III Chairman:: J. D. Fox
    • III.A. A PEDESTRIAN APPROACH TO THE INTERMEDIATE STRUCTURE IN PHOTONUCLEAR REACTIONS IN LIGHT NUCLEI
      (pp. 124-162)
      F. B. Malik and M. G. Mustafa

      In talking about the photonuclear or any other type reaction theory in nuclear physics, it has become customary to classify them into two distinct catagories,vizthe direct reaction (referred to as DR) and the compound process (denoted further as CP). The basic underlying picture of a DR is outlined in Figures 1a and 1b. A photon of energy hν being incident on a nucleus knocks out one of the nucleons, leaving the rest of the system essentially unperturbed. At best, the effect of the rest of the nucleus can be incorporated in terms of a smooth background of an...

    • III.B. The Fine Structure of Analog States
      (pp. 163-191)
      G. E. Mitchell

      The discovery of analog states in medium and heavy nuclei and the subsequent renaissance of interest in isospin is well known and well documented.1-3In this talk it is impractical to give more than cursory attention to the history of analog states, but we should give credit to the pioneering work of Anderson⁴ and collaborators (the observation of analog states via the (p,n) charge exchange reaction), of Lane⁵ (the Lane potential), of Fox, Moore and Robson⁶ (observation of analog states in the compound nucleus), and of Robson⁷ (first theoretical description of compound nuclear analog states).

      The aspect of analog states...

  7. Session IV Chairman:: E. K. Warburton
    • IV.A. NUCLEAR LIFETIMES THROUGH THE USE OF THE CRYSTAL BLOCKING TECHNIQUE
      (pp. 192-214)
      G. M. Temmer

      Considerable experience has been gained over the past decade concerning the remarkable effects of the penetration of charged particles through crystal lattices, the so-called "channeling" and "blocking" phenomena. For our purposes, we shall have reference mainly to the latter, which deal with the suppression, along crystalline axes and planes, of nuclear reaction yields of secondary charged particles from nuclei situated at lattice sites. The incident beam travels along a random direction. Figure 1 illustrates this situation for "prompt" secondary particles obtained from (elastic) Rutherford scattering, for example The detector reveals an angular distribution pattern, when normalized to reaction yield for...

    • IV.B. DOPPLER SHIFTS WITH GAS BACKING
      (pp. 215-224)
      D. J. Donahue

      The Doppler shift attenuation (DSA) method has proved to be a powerful and widely used tool for the measurements of mean lives of nuclear states. As generally used, with nuclei in excited states recoiling into solid backings, mean lives from a few picoseconds down to nearly 10−14seconds can be measured. In the experiments which I will discuss, nuclei recoil in a gas, and thus depending on the gas pressure used, mean lives from a few picoseconds up to nanoseconds can be measured.

      The recoil distance, or plunger method, is generally used for mean lives in this range. However, if...

    • IV.a. PULSED BEAM DIRECT TIMING LIFETIME MEASUREMENTS USING Ge(Li) DETECTORS
      (pp. 225-230)
      Barry C. Robertson

      The Ge(Li) detector has received extensive use because of its excellent energy resolution, but relatively little work has been done with it as a timing device due to the complexity of its pulse shape. However the development of the constant fraction trigger¹ and the amplitude and risetime compensation (ARC) technique² has changed this and made it possible to increase the range of lifetimes that can be measured by the direct timing technique using Ge(Li) detectors.

      In the direct timing technique both the generation and decay time of a nuclear level are measured; the lifetime of a long-lived state can be...

  8. Session V Chairman:: L. Brown
    • Introductory Remarks by the Chairman
      (pp. 231-232)
      Louis Brown

      Previous Symposia have not included sessions on polarization. This was not an oversight on the part of the organizers but reflected the small contribution that this branch has made to nuclear spectroscopy during the first score years of its life. Indeed at the 1970 International Symposium on Polarization in Madison, G. R. Plattner surveyed what had been accomplished in the study of compound nuclear states in light nuclei, concluding that it was almost zero, if the number of level parameters determined using the technique was a measure. I was quite flattered by his talk because he used measurements and analyses...

    • V.A. POLARIZED BEAMS IN NUCLEAR SPECTROSCOPY
      (pp. 233-271)
      H. F. Glavish

      There are two specific applications of polarized beams in nuclear spectroscopy which I shall discuss. One of these is the study of the giant dipole states of nuclei observed with the polarized proton capture reaction A(⃗p,γ)B. The other is the study of particle-gamma correlations following a nuclear reaction that is initiated by a polarized incident beam. An example of this latter application is the study of the angular correlation of gamma rays detected in coincidence with inelastically scattered protons produced by a polarized incident proton beam in a (⃗p,p'γ) reaction.

      In the case of the giant dipole states of nuclei...

    • V.B. BAND STRUCTURE OF Ne20
      (pp. 272-300)
      T. K. Alexander

      The nucleus Ne20has been known to exhibit rotational-like motion for some years.¹ The low lying energy levels have been classified into bands with members having energy spacings proportional to J(J + 1) and the same parity. Levels of one band have E2 transition probabilities many times the single particle value and the observation of such strong E2 transitions has been a major experimental tool in assigning a particular level to a particular band. Recent experiments2,3have shown that the E2 γ ray transition probabilities between all members of the ground state band up to J = 8 are in...

  9. List of Participants
    (pp. 301-302)