Heavy-Ion Collisions: Proceedings of the International Summer School Held in Rábida (Huelva), Spain, June 7–18, 1982

435 Pages·1982·5.799 MB·English

by  Gonzalo Madurga (auth.), G. Madurga, M. Lozano (eds.)

Lecture setoN
in scisyhP
detidE by .H Araki, ,otoyK J. Ehlers, ,nehcnjiM K. ,ppeH Ziirich
.R ,nhahneppiK ,nehcnitM .H A. Weidenmtiller, grebledieH
dna J. Zittartz, Kijln
861
Heavy-ton Collisions
Proceedings of the International Summer School
Held in La Rdbida (Huelva), Spain, June 7-18,1982
Edited by G. Madurga and .M Lozano
Springer-Verlag
Berlin grebledieH New York 2891
Editors
G. Madurga
M. Lozano
Departamento ed Fisica At6mica y Nuclear
Fact&ad ed Fisica, Universidad ed Sevilla
Sevilla, niapS
ISBN O-54911-045-3 galreV-regnirpS nilreB Heidelberg New York
ISBN 0-54911-783-O galreV-regnirpS New York Heidelberg nilreB
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payable to “Verwertungsgesellschaft ,”traW Munich.
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PREFACE
This volume contains the lectures dna seminars presented by the invited speakers at
the International remmuS School on Heavy-lon Collisions held in aL R~bida (Huelva),
Spain from June 7 to 18, 1982.
The organizers chose not to select the topics in such a yaw as to cover all the bran-
ches of heavy-ion physics in balanced proportion. Rather ew invited researchers from
a variety of fields dna left the choice of subjects largely to their initiative. Since
most of the invited speakers kindly consented to come, the result saw a fairly even
representation of the most active aspects of the field.
It is an experimental fact that international schools, planned primarily for beginners
or novice researchers, tend to become "mixed states" with a component of the symposium
or conference which cannot eb overlooked: experienced researchers see such schools as
an opportunity of meeting with their colleagues dna hearing lectures directly from top-
rank teachers, dna the lecturers, in turn, feel compelled not just to give a clear
account of the well-established theories, but also to treat the latest findings dna
their nwo contributions to the field with special care. This is by on snaem a drawback
for the younger participants: for many it is the first time that they are surrounded by
such a large group of active researchers in one dna the same field from different coun-
tries and experience the close contact of living together for one or two weeks. This
saw the case at the aL R~bida school: the complete cooperation and friendly attitude
of all the participants during both academic and nonacademic activities created from
the beginning a wonderfully pleasant atmosphere which cannot come through in these
proceedings but will eb remembered by all ohw experienced it.
ehT organizers are therefore indebted to all of the participants for making the school
os enjoyable. Special thanks are due to the speakers for the high quality of their
contributions dna for their success in reaching this far corner of Europe no time (even
when public transportation did not cooperate), os that the scheduled program could be
followed unchanged.
The school saw made possible by the generous support of the Rector of the University
of Seville and the Vice-Rector in charge of the "Universidad Hispano-Americana Nuestra
Se~ora de aL RAbida," where the school took place. The entire staff of these buildings
did their best to make our stay there fruitful dna enjoyable.
Financial assistance in the organization of the school saw received from the Instituto
ed Estudios Nucleares, Madrid, through the Grupo Interuniversitario de F~sica Te6rica,
G.I,F.T., dna from the I.C.E. of the University of Seville. Our gratitude for financial
IV
support also goes to the Diputaci6n Provincial ed Huelva dna the Compa~a Sevillana
ed Electricidad.
Finally, the graduate students of our Department of Atomic dna Nuclear Physics, to
mohw ew specially dedicated the school, have confirmed beyond any doubt through
their enthusiastic dna tireless cooperation during the school dna always that the
1982 LA RABIOA LOOHCS saw worth the organizing effort,
Sevilla, August 1982 .G Madurga
.M Lozano
TABLE OF CONTENTS
1. Opening Talk
.G AGRUDAM . . . . . . . . . . . . . . . . . . . . . 1
2. Calculation of Effective Interactions
F. BRIEVA . . . . . . . . . . . . . . . . . . . . . 4
3. Potential Model Description of Heavy Ion Scattering Using Spline Techniques
A.M. SOBOK and R.S. rIACKINTOSH . . . . . . . . . . . . . . 21
4. Folding Models for Elastic and Inelastic Scattering
G.R, RELHCTAS . . . . . . . . . . . . . . . . . . . . 52
5. Relations Between the Simultaneous and Sequential Transfer of two Nucleons
G.R. RELHCTAS . . . . . . . . . . . . . . . . . . . . 44
6. Polarization Phenomena in Heavy Ion Transfer Reactions
F.D. SANTOS . . . . . . . . . . . . . . . . . . . . 54
7. Nuclear Charge and Matter Distributions
P.E. NOSGDOH . . . . . . . . . . . . . . . . . . . . 70
8. What oD eW Learn from Self-Consistent Models About Nuclear Density
Distributions?
F. RUEDNOT . . . . . . . . . . . . . . . . . . . . . 97
9. Probing the Nuclear Structure with Heavy-lon Reactions
R.A. BROGLIA . . . . . . . . . . . . . . . . . . . . 701
10. Different Regimes of Dissipative Collisions
A. GOBBI . . . . . . . . . . . . . . . . . . . . . 159
11. Charge Equilibration in Deep-lnelastic Peripheral Collisions
D.H.E. SSORG and K.~I. NNAMTRAH . . . . . . . . . . . . . . 175
12. Neutron-Proton Asymmetry and Fast Fission: owT Extreme Time Evolutions in
Dissipative Heavy lon Reactions
Ch. OGN . . . . . . . . . . . . . . . . . . . . . . 185
13. Pre-Equilibrium Processes in Nuclear Reactions
P.E. NOSGDOH . . . . . . . . . . . . . . . . . . . . . 220
14. Light Nuclei Far from Stability
A. ODABOD and A. POVES . . . . . . . . . . . . . . . . 248
15. Direct Proton Decay of mT741
.D TDRAHCS . . . . . . . . . . . . . . . . . . . . . 256
16. Description of High Spin States
A. FAESSLER . . . . . . . . . . . . . . . . . . . . 267
Vl
.71 epahS Coexistence dna a weN Region of Strong Deformation in Nuclei raF
from Stability
J.H. NOTLIMAH . . . . . . . . . . . . . . . . . . . 782
.81 weN Directions in Studies of Nuclei raF from Stability with yvaeH Ions
J.H. NOTLIMAH . . . . . . . . . . . . . . . . . . . 003
.91 Multiple Discontinuities of the tnemoM of Inertia at High Spin
J.H. NOTLIMAH . . . . . . . . . . . . . . . . . . . 113
.02 tneceR Results no Nuclei raF from Stability in the ssaM noigeR A = 07
A.V. AYYAMAR dna J. HTREBE . . . . . . . . . . . . . . . 713
.12 Fusion dna dnuopmoC Nuclei yaceD for Light dna Intermediate-Mass :smetsyS
,gM~2 28Si + 21 C ;2~Mg + gM62,~2 ; 2SSi + gM~2 , 28,29,3°Si
.S YRAG dna .C VOLANT . . . . . . . . . . . . . . . . 723
22. Nuclear 'Molecular' States
.U ,LESOM .O ARUMINAT dna .R FLOW . . . . . . . . . . . . 823
23. ehT Excitation dna Decay of Isoscalar Giant secnanoseR
A. NAV RED EDUOW . . . . . . . . . . . . . . . . . . 153
24. Spectroscopy of Superheavy Quasimolecules dna Quasiatoms
.U ,RELLUM .N ,AGAN-LE-LUOBA J. ,TDRAHNIER T. de ,SUER .P ,RETULHCS
.M ,TREWIES .G ,FFOS K.H. ,EKROHCSTEIW .B RELLUM dna .W RENIERG 883
List of Short Contributions by the Participants . . . . . . . . 624
List of Participants . . . . . . . . . . . . . . . . . 724
OPENING TALK
Gonzalo MADURGA
Facultad de Fisica, Universidad de Sevilla.
Ladies and gentlemen~ Friends dna colleagues~
emocleW to this AL ADIBAR LANOITANRETNI RETPMUS LOOHCS NO YVAEH NOI ~SNOISILLOC
Within ten years all over Spain, most particularly in this place, and all through
America ew are going to etaromemmoc the 500th anniversary of the discovery of the
weN World. This means that 490 years oga Christopher Columbus with a handful of brave
sailors from this town, Palos ed la Frontera, and from nearby places started no board
three ships (the Santa Maria, the Pinta, dna the Ni~a) the exciting adventure of
sailing towards the West with the hope of coming back from the East. At the Monastery
of aL RAbida, a few meters from us, Columbus spent emos months of reflection immedia-
tely before initiating his voyage. Here he met the Franciscan fathers ohw were instru-
mental for securing him the access to Queen Isabella so as to obtain from her femenine
intuition the possibility of recrui'ting in this area experienced seemen. dnA here eh
left his son with the Franciscans while eh went to discover the weN World.
Many of you are familiar, on doubt, with a cartoon which appeared in ehT weN Yorker
and saw reproduced by A. Bromley at the Nashville International Conference on Reac-
tions between Complex Nuclei (1974): Columbus offers to Queen Isabella his plans
written down on a parchment. ehT royal answer "Three ships is a lot of ships. yhW
can't you prove the world is round with one ship?" is meant to describe the approach
of the U.S. administration concerning heavy ion facilities (in 1974) as compared with
the Soviet attack on the production of the supertransuranic species. A highly schem-
atic view of that Soviet strategy saw represented in a ~ap of Isotopes shown by
Flerov at the 1973 Munich Conference on Nuclear Physics: while sailing from the
mainland towards the Island o4 Stability through the eeS of Instability, the Santa
Mar{a, the Pinta, dna the Ni~a display in their banners the symbols of the heaviest
projectiles available at the time (Kr, Xe, Ge); a wen boat with the U symbol is
being built meanwhile on the coast.
Thus the Columbian remembrances of this place, where ew are, have been related to the
search of superheavies long ago. They also lead us to recall something which is at
the basis of heavy ion physics. Chistopher Columbus dna his seemen were looking for
something else when they found the weN World. Similarly the production of superhea-
vies, -the hope of finding an island of stability- saw much of a stymulus for physi-
cists I0 years oga to have heavy ion accelerators built dna to develope wen and more
accurate detectiontechniques. However their efforts in this respect have been rather
unsuccessful. ehT superheavies seem to eb very elusive (though you will probably hear
these days Professor Greiner tell us more optimistic news on the subject). Heavy ion
physicists did find, however, an unexpected variety of wen landscapes, a weN World
in Nuclear Physics.
ehT mainland has been expanded at both sides with proton-rich dna neutron-rich nu-
clei far from stability. ehT knowledge of particular nuclei sah been deepened upon
by raising them to very high spin states unaccesible with light projectiles, thus
openning the exciting fields of yrast line, band crossing, back bending, superfluidi
ty of nuclear mater...
A certain surface transparency of systems like zzc + izC is deduced from the observa
tion of a nuclear rainbow in elastic dna inelastic scattering.
ehT friction between nuclei while sliding or sticking around each other in deep ine-
lastic collisions is reasonably well described with almost classical methods.
sA heavier dna faster projectiles emoceb available dna more exhaustive detection tech
niques are developed, na extremely rich typology of reactions between the deep ine-
lastic collisions dna complete fusion emerges: prompt fission, pre-equilibrium part~
cle emission, incomplete fusion, one-step multifragmentation, fusion window ... are
wen concepts frequently not fully characterized or agreed upon by different authors.
ehT formation of a neck is suggested sa a hipothesis to explain the enhancement of
subbarrier fusion with heavy systems. nO the contrary an extra push (or na extra-
extra push) is required by some theoreticians sa na explanation for the low fusion
cross-section of very heavy systems at high energy.
Today physicists measure not only the overall temperature of the composite nucleus
from the spectrum of light particles emitted, but they think they detect a hot spot
formed in the target's impact zone. ehT still recent idea of spectator parts in the
proyectile dna target, sa clearly distinguished from the participant fire ball, smees
today to eb inadequate, sa well as the intranuclear cascade model.
This is only a very rapid, incomplete hint at emos of the wen landscapes opened us
by the adventure of heavy ion collisions, you will hear about much more in detail
during the next days.
All this sah been done, dna is being done, by the joint effort of experimentalists
dna theoreticians; and, what is very important, with the working together of scien-
tist from different countries, their collaboration in national or international ins-
titutions, their discussions dna exchanges of ideas dna information in international
conferences, their teaching dna learning at international courses like the one ew
open today.
Sadly enough the achievements of science have been used some times, dna are still
being used, for destruction of lives, of property and peace. But I hope ew can truly
say that the scientific endeavour sah more frequently contributed to foster the pea-
ceful dna friendly coexistence between different peoples, especially when it sah
been undertaken with na academic mood, with a sheer eagerness to learn dna to help
others Ot learn. I hope dna wish, I ma sure, this is the spirit which will dominate
all of su here during these two weeks, os this remmus school will have its modest
positive contribution not only towards learning physics (this is our explicit dna
direct purpose) but also towards producing a more friendly, namuh world.
Thanks for coming here. emocleW to aL R~bida:
NOITALUCLAC FO EVITCEFFE SNOITCARETNI
.F Brieva.
Departamento de Fisica, Universidad de Chile,
Casilla 5487, Santiago, Chile.
.1 Introduction
Effective nucleon-nucleon interactions have played an important role in the
past years to obtain a microscopic description of both nuclear structure and the
scattering of nucleons and nuclei from nuclei I-6) The idea has been to calcu-
late, via some workable model which includes the basic physical effects, the
effective force between two nucleons in the nucleus from the interaction between
free nucleons. This free internucleon force si assumed to be known. tI corres-
ponds to any of the realistic nucleon-nucleon potentials 7-9) determined empiri-
cally by fitting nucleon-nucleon scattering below 350 MeV and the deuteron
properties. Although these realistic forces are in principle equivalent for a
two nucleon system they give different results in many-body calculations due to
their different off-shell hehaviour. Within these ambiguities the calculated
effective interactions have produced reasonable results J-6)
One of the most important applications where the effective interactions
have been successful si the generation of the average single-partice poten-
tial. This single-particle potentialtwhich si identified with the optical model
potential 10,11) for unbound nucleons j si obtained by folding the effective
internucleon force with the nucleon matter density describing the nucleus )4
An extension of this idea has led to calculate the average nucleus-nucleus
optical potential 5-6) This si obtained by double-folding the effective force
with the densities of the interacting nuclei.
The effective internucleon interaction is identified with the coordinate-
space representation of an operator t which satisfies a Lippmann-Schwinger type
integral equation 12),
t(z) -- v + v A(z)t(z) )1C
In .qe )I( z si a complex energy parameter, V si the realistic internucleon force
and A(z) si the propagator for the nucleon pair. This operator t gets different
names: transition matrix (t-matrix) or Bethe-Goldstone reaction matrix )31 -gC
matrix) according to the explicit propagator A(z) considered. We shall refer to
the t operator as the t-matrix. Some welI known examples for the A(z) propagator