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HOMER DUPRE HAGSTRUM
March ~ I, 95-September 7, 1994
BY PHILIP W. ANDERSON AND
T H E O D O RE H . GE BAL L E
HOMER HAGSTRUM WAS BORN in St. Paul, Minnesota. His
father, Andrew, hac! emigrates! there from VarmiancI,
Swollen, as a 22-year-oIcl with his oIcler brother, Nels, in
ISS9. His mother, Saclie Gertrude Fryckberg, was born in
St. Paul in ISS3, the youngest daughter of a family that hac!
also migrated from Swollen. Homer was the second of four
boys who reached maturity. The home environment was
built upon strict Swedish Covenant practices, with a strong
emphasis on education. Drinking, dancing, card playing,
and movies were considered sinful.
Homer continues! to live at home throughout his graclu-
ate years at the University of Minnesota, en cl clicl not see a
movie until he was 25 years oIcl en cl really to go forth into
the woricI. His going to see "Captains Courageous" actually
causecl his mother to break clown en cl weep. She hacl gone
from high school to work when her father cliecl en cl was
cleterminec! that her sons shouic! obtain as much education
as they couIcl absorb. His father, with only an elementary
school experience in Sweden, became the owner with his
brother of a successful men's clothing store, Hagstrum Broth-
ers, in St. Paul. The oIclest son, lean, although groomed to
become a minister, later became a clistinguishecl professor
of English at Northwestern University in Evanston, Illinois,
47
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B I O G RA P H I C A L
EMOIRS
en c! sometime heat! of the National Endowment for the
Humanities. The youngest two brothers, Vincent en cl Paul,
became executives in the mercantile worIcI. Homer en cl lean
hac! the unusual distinction of being awarclec! honorary cle-
grees together from their alma mater, the University of Min-
nesota, cluring the commencement clay of 1986.
Homer roller-skatec! to a local elementary school, where
he attenclecl an alpha class that covered two years' work in
one year. In middle school he skipped half of his eighth-
gracle class. Homer later felt that being much younger than
his classmates was a distinct social handicap. At home he
showocl a strong mechanical aptitude, with a workshop en cl
darkroom in the basement en c! a crystal radio set in the
attic. The high school Homer attenclecI, Minnehaha AcacI-
emy, was a private religious school in Minneapolis. He hacl
begun questioning his famiTy's religious doctrine early on,
en cl in high school became engaged in science. He was
fortunate to have an excellent science teacher, Henry
Schoultz, who profoundly influencer! his life. Even as a fresh-
man Homer stayed after school and worked in Henry's labo-
ratory.
In his senior year Homer and Henry built a 6-inch re-
flecting telescope, which remained at the school for many
years. At home Homer built an "observatory," a portable
wooden structure, to perch on the apex of the roof of his
house. Homer sat up observing with star charts en cl flash-
light for years afterwards. A photograph shows Homer sit-
ting on the steep roof with one of his telescopes in hand.
His early interest in science, astronomy, en cl mathematics,
en cl in working with his hands, never climinishecl en cl gave
him great pleasure for the rest of his life. In later years he
arranged vacations so he couIcl observe solar eclipses even
when they were in faraway places, such as Africa where he
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HOMER DUPRE HAGSTRUM
49
camper! in the desert with his son, Jonathan en c! South
America.
Homer entered the University of Minnesota as an elec-
trical engineering student, obtaining his B.S.E.E. in 1935
summa cum laucle en cl also his B.A. in 1936. While at the
university he clevelopecl a lifelong love of classical music
en c! clelightec! later on in relating how he hac! learner! about
music while "ushering uncler Ormancly en cl Metropolis."
Homer founcl physics to be his natural home en cl went on
to graduate school, completing his M.S. in 1939 en c! his
Ph.D. in physics en cl mathematics in 1940. He became the
last graduate student of John Tate, who is well known, in
aciclition to his own scientific achievements, for being the
longtime editor of Physical Review. Tate was the second
major influence in Homer's scientific life. His first two pa-
pers, publisher! with Tate in 1941, were concerned! with the
ionization en cl dissociation of molecules by electron im-
pact, and with the thermal activation of the oxygen mol-
ecuTe.
Homer left Minnesota in 1940 to join Bell Telephone
Laboratories where he remained for 45 years, his entire
professional career. Bell Labs was then at its West Street
location in downtown Manhattan, en cl Homer found an apart-
ment nearby. He hacl time after work to go out with friends,
discovering opera, ballet, ballroom ciancing which he took
up with enthusiasm en cl skiing. It was at a ski resort on
the slopes of the Berkshires in Massachusetts that he met
Bonnie Cairns from Woocistock, Illinois, who was interested!
in art en cl sculpture. In contrast with the 25 years it took
him to leave his first home, it took only six months before
he en c! Bonnie were marries! in 1948. On a trip to Europe
in 1955 Homer found a decrepit armilIary sphere on the
floor of an antique shop in Florence, Italy. Bonnie pitched
in her half of the travel funcis to produce the 60 clollars
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B I O G RA P H I C A L
EMOIRS
neeclec! to buy it. Homer undertook the stucly of armillaries
upon returning home en cl repaired en cl reconstructed the
instrument, which ciatecl from the sixteenth century. It be-
came one of his en c! the famiTy's most prizes! possessions.
After the war Homer en cl Bonnie movecl to Summit,
New Jersey, near Murray Hill, where the research effort of
Bell Labs was relocatecI. They hac! two chiTciren, Melissa
en cl Jonathan, en cl raisecl them in a comfortable suburban
setting. The chilciren completecl graduate school, each ob-
taining a Ph.D.: Jonathan's in geology and Melissa's in an-
thropology.
A large number of physicists en cl other scientists hacl
come from all over the woric! to join Bell Labs. Because of
far-flung origins en cl the absence of local family en cl oIcl
friends, strong new ties were cemented. The Hagstrums'
close friencis incluclec! Joyce en c! Phil Anderson, John en c!
Maggie Gait, Ted and Sissy Geballe, Bruce and Joan Hannay,
Davicl en cl June Thomas, Peter en cl Cathy Wolff, en cl of
course, many others. The group met throughout the year,
celebrating major holidays, going on outings with children,
and on forays to Manhattan for symphonies and plays off
en c! on Broadway. After a few cirinks Homer lover! to recite
German poetry and sing Swedish hymns. He enjoyed a good
winter hike in the Great Swamp, en cl ice-skating with his
en c! other chiTciren. Later in life he especially lover! hiking
in high alpine terrains with beautiful nighttime skies. He
became a pillar of the Unitarian Church, whose minister
lake Trapp was the father of Bernc! Matthias's wife, Joan.
Homer was clevotecl to his family. He actively encour-
aged Bonnie to clevelop her own talent as a sculptor en cl to
travel to northern Italy to study en c! work in the local marble.
Bonnie's work in stone is highly regarded. Some was shown
in an exhibition at the National Academy of Sciences in the
spring of 1991. In contrast to the Bible camp where Homer
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HOMER DUPRE HAGSTRUM
51
spent his youthful summers, his chiTciren went to camps
with an outdoor orientation. Upon returning one summer
from a camp in New Mexico, Jonathan brought home a
wiTc! bull snake for a pet. Initially the snake escapee! regu-
larly from its terrarium en cl roamed the house at will. Homer,
in particular, was fascinated by the snake's mocle of loco-
motion en c! wouic! bring it out to show guests, usually to
their great dismay. Jonathan later flew the snake back to its
natural habitat.
Homer's professional life was spent at only two institu-
tions the University of Minnesota, where he was eclucatecI,
en cl Bell Labs, where he clicl his pioneering research. His
thesis was a characteristically careful en c! definitive investi-
gation of the ionization en cl dissociation of molecules by
electron impact en cl on the thermal activation of the oxy-
gen molecule. His first two publications resulting from this
work were publishecl (naturally in Physical Review) with
Tate in 1941. Homer went straight to Bell Labs in 1940 en cl
joiner! the physical electronics group uncler Jim Fisk. That
group was responsible for cleveloping and, at first, manu-
facturing the "strapped" microwave magnetron that became
the core element in the Allies' racier superiority cluring the
war. One of the first clozen the English macle was cleliverecl
to the United States by the famous Tizard mission of Sep-
tember 1940, en c! within a month Bell Labs hac! uncler-
taken the responsibility of producing them. In the whole
battle of the black boxes this en cl the early warning racier
were most responsible for turning back the Germans in the
crucial early battles on which Englancl's survival clepenclecl-
in the case of the magnetron the Battle of the Atlantic of
1941. Fisk, Hagstrum, en c! Paul Hartman clescribec! the work
in a postwar paper in the Be]] System Technical To urn e]
(1946~. Others who were involved include J. R. Pierce, J. C.
STater, l. P. Moinar, en c! A. H. White. In later years Homer
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52
B I O G RA P H I C A L
EMOIRS
enjoyed! telling stories about his trip to Englanc! with John
Pierce cluring the war in connection with this work en cl
about the games with "fly-powerecl airplanes" the group in-
ventec! to relieve the pressure of their work. He remained!
close friends with Acl White en cl Julius MoInar.
In 1946, with wartime priorities no longer dictating re-
search, Homer returnee! to the stucly of dissociation by elec-
tron impact measuring the dissociation energies of impor-
tant molecules such as nitrogen, oxygen, carbon clioxicle,
en c! nitric oxide (1951~. The success of the experiments
required ever improving the acivancecl vacuum techniques.
Homer en cl H. W. Weinhart publishecl a calibratecl leak
macle from a porcelain roe! (1950), but in fact his real con-
tribution was in setting, en cl then breaking again en cl again
in the course of the years, records for vacuum pressure en cl
other measures of cleanliness ~ ~ 976, ~ ~ .
In the early 1950s Homer turned his attention to the
interaction of ions with metal surfaces (1960~. His first pa-
per was on electron ejection from Mo by He+, He++, en c!
Her++ (1956~. Homer recognized that this process could be
turned into a new kind of spectroscopy: ionization neutral-
ization spectroscopy (INS). This requires! new instrumenta-
tion, new experimental protocols, en cl new theory, all of
which Homer took on en cl succeeclecl in arriving at work-
able solutions. This lee! to his first paper, in 1953, on the
instrumentation en cl experimental procedure. The theory
of the neutralization process at the solicl surface turns out
to be a complicates! two-electron quantum problem. As the
slow ion approaches the surface some of the large neutral-
ization energy (i.e., the negative of the ionization energy of
the atom) goes to emitting an electron from the surface
while the second electron falls into the ion. The spectro-
scopic information is contained in the kinetic energy distri-
bution of the electron emitter! from the surface. Homer
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HOMER DUPRE HAGSTRUM
53
consiclerec! two relater! paths (1954, 1961), the first being a
direct Auger following the theory of S. S. Shekhter V Exp.
Theor. Phys. ~U.S.S.R.] 7~19371:750) en cl the second being
more complex, involving resonance neutralization follower!
by Auger cle-excitation (H. S. W. Massey, Proc. Camb. Philos.
Soc. 26~19301:386~.
Many of Homer's wartime associates who were still at
Bell hacl been tapped for higher administration, mostly on
the technical sicle. During the immediate postwar years he
continues! to work in the physical electronics group, which
clicl research mostly relatecl to vacuum tubes. But this group
was also minecl for administrative talent, in view of the ex-
pectation that heater! cathodes en c! vacuum technology wouic!
soon be superseclecl by solicI-state crevices. From this group
came, for instance, MoInar, K. G. McKay, John Hornbeck,
en c! its heacI, Aciclison White, as higher-level managers, sev-
eral eventually went on to have very clistinguishecl careers
in management.
Homer, along with Conyers Herring, represented! to the
next generation such as ourselves the possibility of a sec-
oncl fruitful track within the expanding Bell Labs, a career
staying within the cutting ecige of funciamental science without
succumbing either to the blanclishments of academia or
the technical management route. But in 1954 the Bell acI-
ministrators recognizes! that surface physics was becoming
an ever more important frontier in science en cl in technol-
ogy. New en cl improved methods for characterizing surfaces
were neeclec! in semiconductor physics en c! technology, as
well as in heterogeneous catalysis en cl biology. One of the
first interclisciplinary research departments with expertise
in physics, chemistry, en c! metallurgy but focuses! on a
single subfielcI, surface physics was organized with Homer
as department heacI. Siciney MilIman, his perceptive labora-
tory director, undertook to relieve Homer of the most bur-
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54
B I O G RA P H I C A L
EMOIRS
densome administrative duties in order to free his research
time. Within a few years there were other interdisciplinary
departments such as biophysics.
Homer recognized that INS had potentially more sur-
face sensitivity than the more widely used sensitive soft X-
ray scattering (SXS) and photoemission spectroscopies (PES).
But more accurate INS data were required. It took Homer
five years of sustained research to design and construct a
new apparatus that pioneered by incorporating a low-en-
ergy electron-diffraction insert for being able to investigate
the surface symmetry and reconstruction. In the course of
this work he introduced the concept of a turret within which
the sample could be maneuvered to allow a number of dif-
ferent probes or coatings to be applied to the same surface,
a methodology that was widely applied. The apparatus for
INS and the procedures for the data analysis are described
by Homer in a comprehensive article ~ ~ 966, ~ ~ . He was
awarded the Medard W. Welch Award by the American
Vacuum Society in ~ 974. In ~ 976 he was elected to the
National Academy of Sciences and was awarded the Davisson-
Germer Prize by the American Physical Society.
With a minimum number of assumptions the relative
probability that an electron at a given band energy in the
solid will be involved in the neutralization process the tran-
sition probability is calculated. It depends upon the ini-
tial and final state densities and upon the transition matrix
elements and final state interactions much as in PES. It
depends upon wave functions outside the surface and is
thus more surface sensitive than the other spectroscopies.
It is also amenable to studies of surfaces containing foreign
atoms. In a series of investigations with Y. Takeishi (1965),
G. E. Becker ~966, ~973), E. G. McRae ~976), and T.
Sakurai (1976, 1979) that continued until his last working
day at Bell, Homer kept taking data. He and his collabora-
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HOMER DUPRE HAGSTRUM
55
tors stucliec! pure well-characterizec! surfaces of the metals
Fe, Co. Ni, Ag, Cu. W. and Mo and the semiconductors Si,
Ge, en cl GaAs. The studies of these surfaces with acisorbecl
oxide, sulficles en c! other chaTcogenicles, en c! hyciricles were
macle, as well as with alkali metals. Among many other re-
sults of interest was the observation of band narrowing at
the surface for Cu en c! Ni, the first observation of surface
resonances in acisorbecl atoms en cl of the kinetics of acI-
sorption. At the time of his retirement he was making the
first measurements of magnetic resonant states in acisorbec!
atoms, though this work was not completecI.
Homer was that rare type of scientist who enjoyocl work-
ing on all aspects of a carefully thought out research pro-
gram, from his initial iclea to the design en cl construction
of the neeclecl apparatus, to the taking of ciata en cl then
mollifying the theory when necessary to obtain a cletailec!
unclerstancling. In the goIclen age of research at Bell Labs
at that time it was possible for Homer to take five years
J 1
from his research to built! the apparatus. Even though he
succeeclecl in establishing INS as a valuccl spectroscopy, it
has not become a standard laboratory practice. The con-
fluence of new clevelopments renclerec! INS of less value
than Homer hacl envisioned. In particular, a spectacular
array of new scanning tunneling probes has come into be-
ing following Hans Rohrer en c! Gerc! Binnig's revolutionary
demonstration of scanning tunneling microscopy in 1984.
There the electron tunneling is by means of wave functions
that extent! from the surface much as in INS. In all other
respects the tunneling tip, which can be accurately con-
trollecl in all three dimensions, is much superior to the
moving ion. INS has been macle obsolete after only two
short clecacles of existence. If there is a lesson to be Earned,
it is that science moves ahead on many fronts en cl the most
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56
BIOGRAPHICAL MEMOIRS
acimirable achievements are not necessarily the most en-
during.
Homer kept taking data right up until the day he re-
tirec! from Bell. He planner! to be engages! in analysis in
the years ahead. Unfortunately, about that time Homer suf-
ferecl a series of small strokes that ciamagecl his short-term
memory en c! impairec! his ability to concentrate. Nothing
that has transpired detracts from Homer's achievements.
While INS will not be remembered as a milestone of twenti-
eth-century physics, Homer Hagstrum will be rememberer!
as a pioneer who created many of the icleas en cl techniques
of moclern surface physics.
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HOMER DUPRE HAGSTRUM
SELECTED BIBLIOGRAPHY
1941
57
With J. T. Tate. Ionization and dissociation of diatomic molecules
by electron impact. Phys. Rev. 59:354.
With J. T. Tate. On the thermal activation of the oxygen molecule.
Phys. Rev. 59:509.
1946
With J. B. Fisk and P. L. Hartman. The magnetron as a generator of
centimeter waves. Bell Syst. Tech. I. 25:167.
1950
With H. W. Weinhart. A new porcelain rod leak. Rev. Sci. Instrum.
21:394.
1951
Ionization by electron impact in CO, N2, NO, and O2. Rev. Mod.
Phys. 23:185.
1953
Instrumentation and experimental procedure for studies of elec-
tron ejection by ions and ionization by electron impact. Rev. Sci.
Instrum. 23:1122.
1954
Theory of Auger ejection of electrons from metals by ions. Phys.
Rev. 96:336.
1956
Electron ejection from metals by ions. Bell Labs Rec. 34~2~:63.
1960
With C. D'Amico. Production and demonstration of atomically clean
metal surfaces. 7. Appl. Phys. 31:715.
1961
Theory of Auger neutralization of ions at the surface of a diamond-
type semiconductor. Phys. Rev. 122:83.
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58
B I O G RA P H I C A L
1965
EMOIRS
With Y. Takeishi. Effect of electron-electron interaction on the ki-
netic-energy distribution of electrons ejected from solids by slow
ions. Phys. Rev. 137:A304.
With Y. Takeishi. Auger-type electron ejection from the (111) face
of Ni by slow He+, Ne+, and Ar+ ions. Phys. Rev. 137:A641.
1966
Ion-neutralization spectroscopy of solids and solid surfaces. Phys.
Rev. 150:495.
With G. E. Becker. Ion-neutralization spectroscopy of copper and
nickel. Phys. Rev. Lett. 16:230.
1967
With G. E. Becker. Ion-neutralization spectroscopy of copper and
nickel. Phys. Rev. 159:572.
1971
With G. E. Becker. The interrelation of physics and mathematics in
ion neutralization spectroscopy. Phys. Rev. B 4:4187-4202.
1973
With G. E. Becker. Folding and nonfolding electron distributions
in ion neutralization spectroscopy and evidence for an electronic
superlattice at the Si(111~7 surface. Phys. Rev. B 8:1592-1603.
With G. E. Becker. Resonance, Auger, and autoionization processes
involving He+~2s) and He++ near solid surfaces. Phys. Rev. B 8:107.
1975
With K. C. Pandoy and T. Sakurai. Si~lll):SiH3 A simple new sur-
face phase. Phys. Rev. Lett. 35:1728-31.
1976
With E. G. McRae. Surface structure experimental methods. In Treatise
on Solid State Chemistry, vol. 6A, ed. N. B. Hannay, pp. 57-163.
New York: Plenum.
With T. Sakurai. Interplay of the monohydride phase and a newly
discovered dihydride phase in chemi-sorption of H and Si(100) 2x1.
Phys. Rev. B 14:1593.
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HOMER DUPRE HAGSTRUM
1979
59
With T. Sakurai. Study of clean and CO-covered Ge(111) surfaces
by UPS and INS. Phys. Rev. B 20:2423.
Representative terms from entire chapter:
dupre hagstrum
