Table Of ContentPOSITRON ANNIHILATION
Proceedings of the Conference Held at
Wayne State University on July 27-29, 1965
Edited by
A. T. STEWART L 0. ROELLIG
Department of Physics Department of Physics
University of North Carolina Wayne State University
Chapel Hill, North Carolina Detroit, Michigan
ACADEMIC PRESS · New York · London · 1967
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List of Contributors
Numbers in parentheses indicate the pages on which
the authorsT contributions begin.
G» AMBROSINO (345), Institut National des Sciences et Techniques
Nucléaires, Saclay, France
J. BELL (393), Department of Nuclear and Radiation Chemistry, Uni-
versity of New South Wales, Sydney, Australia
S. BERKO (61,269), Department of Physics, Brandeis University,
Waltham, Massachusetts
W. BRANDT (155), Department of Physics, New York University,
New York, New York
C. V. BRISCOE (377, 383), Department of Physics, University of
North Carolina, Chapel Hill, North Carolina
J. P. CARBOTTE (265),1 Laboratory of Atomic and Solid State Phys-
ics, Cornell University, Ithaca, New York
G. J. CELITANS (365, 371),2 New England Institute for Medical Re-
search, Ridgefield, Connecticut
G. CHANDRA (335), Tata Institute of Fundamental Research, Bombay,
India
P. COLOMBINO (353), Istituto di Fisica dell'Università, Turin, Italy
H. R. CRANE (321), Harrison M. Randall Laboratory of Physics, The
University of Michigan, Ann Arbor, Michigan
N. E. CUSACK (309), Department of Physics, University of East
Anglia, Norwich, England
S. DeBENEDETTI (3, 297), Carnegie Institute of Technology, Pitts-
burgh, Pennsylvania
L. H. DIETERMAN (317), Department of Physics, The University of
Texas, Austin, Texas
Present Address: Department of Physics, McMaster University, Hamilton,
Ontario, Canada.
2Present Address: Department of Physics, The Hiram Scott College,
Scottsbluff, Nebraska.
VI LIST OF CONTRIBUTORS
G. FABRI (357, 421), Laboratorio Centro Informazioni Studi Esperi-
enze, Milan, Italy
A. FIORENTINI (81), Gruppo Nazionale Struttura della Materia del
CNR, Istituto de Fisica del Politecnico di Milano, Milan, Italy
B. FISCELLA (353), Istituto di Fisica dell'Università, Turin, Italy
E. GERMAGNOLI (357), Istituto di Fisica dell'Università, Parma,
Italy
V. I. GOLDANSKII (183), Chemical Physics Institute of the Academy
of Science of the USSR, Moscow, USSR
J. H. GREEN (95),3 Department of Nuclear and Radiation Chemistry,
University of New South Wales, Sydney, Australia
G. IACI (357), Istituto di Fisica deirUniversità, Catania, Italy
G. JONES (401), Department of Physics, University of British Colum-
bia, Vancouver, Canada
S. KAHANA (51),4 Department of Physics, McGill University, Mon-
treal, Canada
T. M. KELLY (387), Department of Physics, Wayne State University,
Detroit, Michigan
T. KOHONEN (277), Institute of Technology, Otaniemi, Finland
V. G. KULKARNI (335), Tata Institute of Fundamental Research,
Bombay, India
J. H. KUSMISS (341 ),5 Department of Physics, University of North
Carolina, Chapel Hill, North Carolina
R. G. LAGU (335), Tata Institute of Fundamental Research, Bombay,
India
G. F. 0. LANGSTROTH (281), Department of Physics, Dalhousie Uni-
versity, Halifax, Nova Scotia, Canada
J. LEE (365, 371), New England Institute for Medical Research,
Ridgefield, Connecticut
3Present Address: New England Institute for Medical Research, Ridge-
field, Connecticut.
4Present Address: Physics Department, Brookhaven National Laboratory,
Upton, New York.
5 Present Address: Physics Department, Western Michigan University,
Kalamazoo, Michigan.
LIST OF CONTRIBUTORS Vll
C. Y. LEUNG (409), Department of Physics, University of Toronto,
Toronto, Canada
T. L. LOUCKS (287), Institute for Atomic Research and Department
of Physics, Iowa State University, Ames, Iowa
J. D. McGERVEY (143, 305), Department of Physics, Western Re-
serve University, Cleveland, Ohio
B. T. A. McKEE (281), Department of Physics, Dalhousie University,
Halifax, Nova Scotia, Canada
A. R. MACKINTOSH (287), Institute for Atomic Research and De-
partment of Physics, Iowa State University, Ames, Iowa
I. K. MacKENZIE (281), Department of Physics, Dalhousie Univer-
sity, Halifax, Nova Scotia, Canada
C. K. MAJUMDAR (299), Department of Physics, Carnegie Institute
of Technology, Pittsburgh, Pennsylvania
H. S. W. MASSEY (113), Department of Physics, University College,
London, England
J. MELNGAILIS (297),6 Carnegie Institute of Technology, Pittsburgh,
Pennsylvania
W. E. MILLETT (317, 361), Department of Physics, The University
of Texas, Austin, Texas
P. H. R. ORTH (401), Department of Physics, University of British
Columbia, Vancouver, Canada
T. M. PATTERSON (349),7 Department of Physics, University of
North Carolina, Chapel Hill, North Carolina
D. A. L. PAUL (409, 417), Department of Physics, University of To-
ronto, Toronto, Canada
R. PAULIN (345), Institut National des Sciences et Techniques Nu-
cléaires, Saclay, France
G. POLETT1 (421), Laboratorio Centro Informazioni Studi Esperi-
enze, Milan, Italy
I. F. QUERCIA (357), Istituto di Fisica dell'Università, Catania, Italy
G. RANDONE (421), Laboratorio Centro Informazioni Studi Esperien
enze, Milan, Italy
6Present Address: Centre National de la Recherche Scientifique, France.
7 Present Address: Physics Department, Wayne State University, Detroit,
Michigan.
viii LIST OF CONTRIBUTORS
A. RICH (321), Harrison M. Randall Laboratory of Physics, The Uni-
versity of Michigan, Ann Arbor, Michigan
D. M. ROCKMORE (259),8 Department of Physics, University of North
Carolina, Chapel Hill, North Carolina
L. O. ROELLIG (127, 387), Department of Physics, Wayne State Uni-
versity, Detroit, Michigan
J. B. SHAND (291),9 University of North Carolina, Chapel Hill, North
Carolina
P. C. STANGEBY (417), Department of Physics, University of To-
ronto, Toronto, Canada
A. T. STEWART (17, 259, 291, 313, 341, 349, 377, 383), Department
of Physics, University of North Carolina, Chapel Hill, North
Carolina
S. J. TAO (371, 393), New England Institute for Medical Research,
Ridgefield, Connecticut
J. H. TERRELL (269),10 Department of Physics, Brandeis University,
Waltham, Massachusetts
J. C. THOMPSON (317), Department of Physics, The University of
Texas, Austin, Texas
B. V. THOSAR (335), Tata Institute of Fundamental Research, Bom-
bay, India
L. TROSSI (353), Istituto Nazionale di Fisica Nucleare, Sezione di
Torino, Turin, Italy
E. TURRISI (357), Istituto di Fisica dell'Universita, Catania, Italy
P. G. VARLASHKIN (313),11 Department of Physics, University of
North Carolina, Chapel Hill, North Carolina
H. L. WEISBERG (269),12 Department of Physics, Brandeis Univer-
sity, Waltham, Massachusetts
8Present Address: Physics Department, University of Maine, Orono,
Maine.
9 Present Address: Department of Physics, University of Georgia, Athens,
Georgia.
10Present Address: Mithras Inc., Cambridge, Massachusetts.
nPresent Address: Physics Department, Louisiana State University,
Baton Rouge, Louisiana.
12Present Address: Lawrence Radiation Laboratory, University of Califor-
nia, Berkeley, California.
LIST OF CONTRIBUTORS IX
R. N. WEST (309), Department of Physics, University of East Anglia,
Norwich, England
R. W. WILLIAMS,(287), Institute for Atomic Research and Depart-
ment of Physics, Iowa State University, Ames, Iowa
E. J. WOLL, Jr. (329),13 Department of Physics, Carnegie Institute
of Technology, Pittsburgh, Pennsylvania
Present Address: Department of Physics, McMaster University, Hamil-
ton, Ontario, Canada.
Preface
This book summarizes the present knowledge of positron an-
nihilation in various environments. The first part of the book
presents lengthy review articles based on the invited talks pre-
sented at the Positron Annihilation Conference These papers
0
were coordinated with respect to each other and written to sur-
vey the entire field. The second section contains short reports of
the most recent developments in the field and illustrates the pres-
ent direction of research.
The study of the annihilation of positrons has provided valuable
information concerning the properties of matter. Positrons make a
useful probe, for they can penetrate into liquids and solids without
damaging the material. The annihilation gamma rays (which are rel-
atively unattenuated by the usual experimental apparatus, e. g. Dewars,
vacuum chamber walls, or high pressure cells) provide information
concerning the structure of the material and its interactions with pos-
itrons. In recent years several important advances have been made,
especially in positron annihilation in gases and metals, and in pos-
itronium chemistry. Furthermore, the commercial development of
fast and stable electronic apparatus has encouraged many more groups
to work in the field so that the rate of progress is increasing rapidly.
A Positron Annihilation Conference was orgainized to help con-
solidate present progress, to discuss unsolved problems, and to dis-
cern new directions of profitable research work for this interesting
and unique method. The conference, held at Wayne State University
in Detroit, Michigan on July 27-29, 1965, was made possible through
the generous support of the Wayne State Fund, University of North
Carolina at Chapel Hill, National Science Foundation, United States
Army Research Office, Durham, and the Advanced Research Projects
Agency (University of North Carolina). The organizing committee,
L. O. Roellig (chairman), A. T. Stewart, and P. R. Wallace, is pleased
to take this opportunity to thank these organizations for their sponsor-
ship.
The editors are much indebted to their colleagues, for it is they
who by contributions and discussions have created this book, a re-
view and guide to positron annihilation in matter.
A. T. STEWART
L. O. ROELLIG
July, 1967
xi
The Physics of Positron Annihilation
A Survey*
S. DeBenedetti
Carnegie Institute of Technology
Pittsburgh, Pennsylvania
THE ERA OF DISCOVERY AND OF QUANTUM
ELECTRODYNAMICAL INVESTIGATION
The opportunity of presenting a historical survey of the develop-
ments in the physics of positrons is both an honor and a pleasure.
The pleasure, however, is somewhat reduced when I think that such
honors are usually conferred on people who are themselves consid-
ered as part of history. And though history is concerned with the
past, I would like to have the illusion that, for the moment, I still do
belong to the present. Do I?
But I am not here to speak of my personal life, but rather about
the life of the positrons.
In this connection I discovered a remarkable coincidence. The life
of the positrons is about as long as my own scientific life. With this,
I do not mean that my scientific life is of the order of 10""9 sec; it
might well be just as ephemeral, but measured in seconds it is closer
to 109 than to 10~9. Perhaps this is because I have not yet met my
antiself! Had my life been of the order of 10~9 sec, I would not have
been invited to give this historical introduction.
When I say that my scientific life is as long as that of the posi-
trons, I refer to the fact that the positrons were discovered by An-
derson in 19331 when I was in the last year of study at the Univer-
sity of Florence.
The news of the discovery did not come to me from Anderson in
California, but from a schoolmate of mine a year or so older than
myself, whose name some of you may remember. I am speaking
about Occhialini who, in 1933, was in England working with Blackett
on the construction of the first counter-controlled cloud chamber.
From my friend Occhialini a letter arrived at the Institute of
*Work supported by the National Science Foundation.
3
4 S. DeBENEDETTI
Physics in Florence telling about the results of his work. At the In-
stitute—which is located in the lovely hill of Arcetri where Galileo
spent the last years of his life under house imprisonment for having
dared to support the Copernican system—the letter was passed on
to me by Bernardini, whose name you may also have heard. This
letter told of the discovery of cosmic ray showers. 2 The pictures of
the showers, which we received, contained both positrons and elec-
trons. Not only did they confirm the existence of positrons, which
had been established quite convincingly by Anderson, but they proved
that positrons were actually produced in the transformation of energy
into matter. This interrelation between matter and energy was a
new thing at the time, and you might understand how it appealed to
the mind of a young student such as I was. It is true that the theory
of relativity was known and that Dirac had predicted the existence of
some positively charge states of the electron (which he himself found
very embarrassing because they had not been found in nature); but,
until these pictures showed the actual creation of matter from en-
ergy, all the theoretical arguments seemed empty speculations. To
see for the first time the creation of particles and antiparticles was
an experience which I still remember and which moved me quite
deeply.
It is probably from that time on that I fell in love with positrons;
in a way I am still in love with them. I must confess, however, that I
have not always been faithful to this love. With the discovery of new
particles, the object of my intellectual affection has been changing.
Some of you might accuse me of being intellectually promiscuous and
it is an accusation I will not dispute.
But, going back to positrons, the next step was the discovery that
they annihilated. The experimental work was done in France (also
published in 1933) separately by Thibaud3'4 and by Joliot.5*6 In the
meantime Monsieur and Madame Joliot had discovered artificial ra-
dioactivity which provided sources of positrons that could be handled
with ease.
For this discovery M. and Mme. Joliot were awarded the Nobel
prize. When the announcement of the prize came, I was working with
them at the Laboratoire Curie, where the occasion was happily cele-
brated by opening numerous bottles of champagne.
It was at this laboratory, under the direction of Joliot, that I be-
came more directly acquainted with positrons. I had the great satis-
faction of seeing how the positrons were actually produced by the
materialization of gamma rays. I used the gamma rays from radio-
active Thorium C" , and was able to verify the law predicted by the
theory that the materialization cross section goes with the square of
the atomic number.7>8 At about the same time, in 1934, Klemperer
was studying some of the features of annihilation, and proved that
two gamma rays were emitted in coincidence in approximately op-
posite directions.9
