Contemporary Research Topics in Nuclear Physics PDF
Preview Contemporary Research Topics in Nuclear Physics
Contemporary Research Topics in NUCLEAR PHYSICS Contemporary Research Topics in NUCLEAR PHYSICS Edited by Da Hsuan Feng and Michel Vallieres Drexel University PhIladelphia, Pennsylvania and Michael W. Guidry and Lee L. Riedinger University of Tennessee Knoxville, Tennessee PLENUM PRESS • NEW YORK AND LONDON Library of Congress Cataloging in Publication Data Main entry under title: Contemporary research topics in nuclear physics. "Proceedings of a workshop held at Drexel University from September 1 to Sep tember 3, 1980, under the joint auspices of Drexel Umversity, the University of Ten nessee, and Vanderbilt University" -Pref. Bibliography: p. Includes index. 1. Nuclear physics-Congresses. I. Feng, Da Hsuan, 1945- II. Drexel Uni- versity. III. University of Tennessee (Knoxville campus). IV. Vanderbilt University. QC770.CC6 539.7 82-3677 ISBN-13:978-1-4684-1136-2 e-ISBN-13:978-1-4684-1134-8 DOl: 10.1007/978-1-4684-1134-8 Proceedings of a workshop on Nuclear Physics, held September 1-3, 1980, at Drexel University, Philadelphia, Pennsylvania © 1982 Plenum Press, New York Softcover reprint of the hardcover 1s t edition 1982 A Division of Plenum Publishing CorporatIOn 233 Spnng Street, New York, NY 10013 All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, mlcrofilmmg, recording, or otherwise, without written permission from the Publisher PREFACE This volume contains the proceedings of a workshop held at Drexel University from September 1 to September 3, 1980, under the joint auspices of Drexel University, The University of Tennessee and Vanderbilt University. The workshop dealt with subjects of topical importance to the nuclear physics community: high spin phenomena, heavy ion reactions, transfer reactions, microscopic theories of nuclear structure and the interacting boson model, and miscellaneous topics. This pro ceedings contains all of the invited papers plus short manuscripts expanding on the materials of the invited papers. A total of about 85 participants came to the workshop. The format of the conference was kept informal on purpose, so as to facilitate the discussions. Unfortunately, these discussions, at times intense, could not be included in this volume due to the lack of secretarial help during the meeting. A great deal of current information was exchanged during the conference. However, the full impact of a conference can only be realized when the proceedings have been published and read by par ticipants as well as other colleagues in this field of physics who were not in attendance. We sincerely hope that these proceedings will be useful in this regard. The Organizing Committee is particularly grateful to the Conference participants for their patience and in helping us pre pare the proceedings. The generous financial help of Drexel Uni versity, University of Tennessee and Vanderbilt University was instrumental in making this conference a reality, and is greatly appreciated. Last but not least, the professional help of Mr. Palliparambil Joseph Antony deserves to be especially mentioned, without which completion of this volume would have been impossible. The Editors v CONTENTS Note: The name in capitals indicates the author who presented the talk. SESSION I: High Spin Phenomena Chairperson: L.L. Riedinger Quasi-Particle Motion in Rotating Nuclei 1 S. FRAUENDORF Nuclear Spectroscopy at Very High and Very Low Rotational Frequencies 29 J.D. GARRETT Dynamic Deformation Theory: Recent Results for Spectra and for Cross Sections 55 K. KUMAR High Spin Phenomena 83 J.H. HAMILTON and C.F. Maguire Interpretation of the 2l-ns Isomer in 109Hg as (Vi13/2)2 from a g-Factor Measurement 103 S.A. HJORTH, I.Y. Lee, J.R. Beene, C. Roulet, D.R. Haenni, N.R. Johnson, F.E. Obenshain and G.R. Young High Spin Studies by Multiple Coulomb Excitation 109 E. GROSSE SESSION II: Heavy-Ions Reactions Chairperson: R.K. Bhaduri On the Transition from the Coherent to the Statistical Phase in Deep Inelastic Collisions 121 U. SMILANSKY, S. Mukamel, D.H.E. Gross and K. Mohring vii viii CONTENTS Excitation of Shape-Vibrational Modes in Nuclei by Relativistic Heavy Ions 141 J.O. RASMUSSEN, J. Blair and X. Qiu Nuclear Charge and Matter Distributions 153 P . E. HODGSON A Study of the Reaction Mechanism for l2C on 209Bi at E(C) = 61.1-73 MeV 177 GEN-MING JIN, Xie Yuan-Xiang, Zhu~ong-Tai Shen Wen-Qing, Yu Ju-Sheng, Sun Xi-Jun, Liu Guo-Xing, Sun Ching-Chang, Gua Jun-Sheng, Wu Zhon-Gli, Xu Shu-Wei, Wu En-Chin and Yang Chen-Zhong and J.D. Garrett SESSION III: Transfer Reactions Chairperson: E. Grosse Inelastic Scattering and Transfer Reactions Using Very Heavy Ions 193 M.W. GUIDRY, R.E. Neese and T.L. Nichols Probing Transitional Regions with Nuclear Transfer 223 Reactions J. VAAGEN 249 Nuclean Reactions Near the Coulomb Barrier J.S. Lilley 275 Heavy Ion Reaction Mechanisms C.F. Maguire and J.H. HAMILTON Heavy-Ion Induced Transfer Reactions to High-J Orbital States 297 J. BARRETTE SESSION IV: Microscopic Theories of Nuclear Structure Chairperson: A. Klein Perturbation Theory for a System of Fermions in a Deformed Basis 309 D.R. BES The Boson Fermion-Hybrid Representation and The Nuclear Field Theory 317 C.L. WO, M.W. Guidry, J.Q. Chen and D.H. Feng CONTENTS Microscopic Calculations of the Fission Barrier of Some Actinide Nuclei with Skyrme-Type Interaction Using a Two-Step Iterative Method 331 A. Dutta, R.K. Bhaduri, I. Easson, M. Kohno and M. Val1i~res Linear_.Response RPA Model to Open Shell Nuclei 341 A. Moa1em and J. Bar-Touv Collective Gyromagnetic Ratio From Density Dependent Hartree-Fock Calculations 349 D.W.L. Sprung, S.G. Lie and M. Va11i~res A Phenomenological Study of Nuclear Currents 357 C.L. Lin Collective Vibrations with Zero Range Skyrme and Delta-Log Interaction 363 A. Abbas SESSION V: Interacting Boson Model Chairperson: E. Marshalek Overview of Experimental Tests of the IBA 369 R.F. CASTEN The Interacting Boson Model in the Continuous Basis Representation 4ll R. GILMORE and D.H. Feng Shell Model Structure of the Interacting Boson Model and the Interacting Boson Fermion Model 435 I. TALMI Testing the Interacting-Boson and Interacting-Boson Fermion Approximations by the Study of Radioactive 4ll Decay Schemes with UNISOR On-Line Isotope-Separator J.L. WOOD Studies of Isotope Series with Effective Boson Hamiltonians 4~ P. FEDERMAN, O. Castanos and A. Frank Use of a Boson Mapping to Elucidate the Relation ship Between the IBM and the Bohr Collective Hamiltonian and between a Simplified Shell Model and the Bohr Collective Hamiltonian 487 A. Klein and M. Val1i~res x CONTENTS Renormalization of the IBA Hamiltonian for the Effects of the g Boson 495 K.A. SAGE and B.R. Barrett The Interacting-Boson-Fermion Approximation 503 O. SCHOLTEN Quantized Bogolyubov Transformation and Microscopic Foundation of IBM 523 LI-MING YANG SESSION VI: Miscellaneous Topics Chairperson: S. Pittel Theory of Nuclear Single Particle Potential 531 SHI-SHU WU Application of The Boson-Fermion Hybrid Representation: Why is Spin-Polarized Atomic Hydrogen a Bosonic System? 563 C.L. Wu, J.M. Yuan and D.H. Feng The Microscopic Mechanism of the (p, ~t) Reaction 5n Liu Bo and Zhang Zong-Ye Supermultiplet Classification and Collective Spectra of Two-Electron Atoms 5~ Michael E. KELLMAN PARTICIPANTS 5~ INDEX 591 QUASIPARTICLE MOTION IN ROTATING NUCLEI S. Frauendorf Central Institute for Nuclear Research Rossendorf, 8051 Dresden, PF 19 German Democratic Republic 1. ABSTRACT The rotational bands of deformed nuclei with high spin can be interpreted as configurations of independent quasipartic1es in a deformed potential rotating with a constant frequency and with a pairfie1d present. This generalization of the shell model to rotat ing potentials is called the Cranked Shell Model (CSM). The classi fication with respect to the symmetry quantum number signature is introduced. Several CSM-predictions, such as the additivity of quasiparticle energies and angular momenta, the occurrence of char acteristic frequencies around which band crossings cluster and the interference between quasiparticle orbits are discussed and compared with experimental data on high spin states in the light rare earth region. II. INTRODUCTION The ascent of heavy ion accelerators has created the possibility to study nuclei that carry as much angular momentum as they can accomodate without fissioning. The region of a few MeV excitation above the yrast line is being intensively studied. In this yrast region the rotating nucleus is cold, i.e. its level density is com parable with that near the ground state. Moreover, it takes the rotating nucleus at least 10-12s to de-excite into the ground state. This time is very long in comparison with the typical nuclear time of 10-22s and the states in the yrast region may be considered as stationary ones. This led to the concept of "Yrast-spectroscopy" which extends the spectroscopy of low lying states to the whole yrast region1 . Recent experimental yrast-spectroscopy of discrete 2 s. FRAUENDORF Y-lines has reached angular momentum of I ~ 30 t 2• The region of higher angular momenta is being explored by studying the Y-continua3 Since the nucleus is cold in the yrast region the mean free path of the nucleons is large enough that the independent particle model is expected to work. The majority of the excited states above the yrast line should correspond to a rearrangement of a few nucle~ onic orbitals. Thus it is obvious to base the analysis of the yrast region on an appropriate version of the shell model. One may dis tinguish two important cases: i. The nucleus rotates about its symmetry axis. The rotation does not directly modify the nucleonic orbits (only via changes of the potential) and one may employ the standard shell model with a spherical or deformed potential. The experimental data are con sistent with such an approachl ,4. ii. The nucleus rotates about an axis perpendicular to its symmetry axis. The rotation of the deformed potential modifies the nucleonic orbits which depend on the angular frequency. The rotation is col lective and the states group into rotational bands. My talk will only deal with case (ii). It is based mainly on the work by R. Bengtsson and S. Frauendorf5,6 (cf. also ref. 1). III. THE CRANKED SHELL MODEL We assume that the deformed shell-model potential rotates with the constant angular frequency w about an axis perpendicular to its symmetry axis. In the frame of reference attached to the poten tial the shell model Hamiltonian reads h' h - wjx (1) where h is a standard deformed shell model Hamiltonian and z and x are chosen to be the symmetry and rotation axis, respectively. We suggest calling the Hamiltonian the "Cranked Shell Model" (CSM) in order to relate it to the Cranking Model. The latter notation (also Cranking HFB) is usually used in the context of a self consistent treatment of the independent particle Hamiltonian (1), providing total excitation energies with respect to the ground state. The simpler CSM continues the tradition of shell models assuming that h does not depend on the configuration; h may depend on w, but so far the consequences of this possibility have not been studied in a detail. As any shell model, CSM aims only at the cal culation of excitation energies with respect to a reference con figuration that depends on the frequency w (a band which is yrast of near yrast~.
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