2000's Laureates
Sheldon Datz, 2000
Citation:
For his career in chemistry and atomic physics, the
unifying feature of which is the dynamics of change
through collision. He has been a pioneer in the fields
of crossed-beam and molecular beam chemistry and atomic
physics, channeling of ions in solids, and in recent
insightful experiments using the apparatus of particle
physics to cast light on the chemistry of the early
universe.
Background:
Sheldon Datz is among the most creative experimental
scientists of our time having distinguished himself as a
leader for more than forty years in atomic, molecular,
and optical physics, as well in physical chemistry, the
field in which he received his doctoral degree. He is
also known for his observation and measurement of
dielectronic recombination, a dominant energy loss
process in fusion-oriented high temperature plasma, and
pair production.
The unifying feature of his forty-five year scientific
career lies in his use of crossed molecular beams to
study the dynamics of chemical reactions in
atom-molecule collisions. His broad contributions have
provided understanding of the mechanisms of interactions
involving ions, electrons and photons with kinetic
energies ranging from a milli-electron volt to many
mega-electron volts; and have engendered new methods for
probing the structure of surfaces and internal structure
of metal crystals. Many of his discoveries have been
seminal in nature, and the breadth of these activities
is truly extraordinary.
In chemical dynamics, Dr. Datz and his colleague Dr. E.H.
Taylor in 1955 published the first paper on the use of
crossed molecular beam techniques to study chemical
reactions could be studied under conditions that would
allow observing properties that revealed the quantum
interactions in single collisions. That result had long
been a dream of chemists, but was presumed to be
completely impractical. The very simplicity of this
experiment made it clear even to young assistant
professors that one could undertake similar experiments
with rather modest investments in instrumentation. In
this first and two succeeding papers, Datz and Taylor
described methods to obtain described the experimental
techniques necessary to study atom-molecule reactions
and methods to obtain the detailed nature of chemically
reactive collisions could be obtained. The famous Datz
and Taylor papers of the 1950s and 1960s laid the
foundation for an entirely new field of crossed
molecular beam chemistry.
Datz' continuing work in this field resulted in the
following: the first use of time of flight to measure
translational to vibrational energy in atom-molecule and
ion-molecule collisions; the first molecular beam study
of the role of electronic excitation in chemical
reactions, and the first demonstration of electronic
energy transfer.
Dr. Datz's interest in ion-surface scattering stemmed
from experiments he conducted that demonstrated for the
first time that single atom-atom collisions could be
studied, even if the target atoms were located on the
surface of a solid. In inelastic-atom-molecule
collisions, he introduced time-of-flight and particle
counting techniques (translational spectroscopy) to
study the transfer of translational to vibrational
energy and dissociative collisions.
Datz has been similarly innovative in experiments
demonstrating ion channeling in solids, an effect
predicted theoretically by M. Robinson. In order to
decrease the contribution of multiple scattering
background in the surface scattering experiments, Datz
used single crystal targets oriented so that the
projectile either hit surface atoms or penetrated so
deeply that they did not return. His experiments in this
field resulted in the following: the first demonstration
of coherent excitation of ions by the periodic potential
in a crystal lattice; the discovery of electron and
positron channeling radiation; the first demonstration
that channeled ions interact with electrons in the
crystal as a dense electron target; and the first
demonstration that one can make quantitative
measurements applicable to collisions in dense plasmas
but with more monoenergetic collision conditions.
His experiments have created a research and training
environment in which young scientists have grown and
flourished. Moreover, he has used his standing in the
international community to promote the exchange of
information among scientists of all nations. For the
past several years, he has been organizing yet another
major international conference which will take place
during his 75th year.
Sheldon Datz was born in New York City in 1927. He
earned his B.S. and M.A. degrees at Columbia University
in Chemistry and Physical Chemistry (1950-51) and his
Ph.D. degree from the University of Tennessee in 1960.
He began his career in 1951 as a research chemist at Oak
Ridge National Laboratory, where he is now Senior
Corporate Fellow. He has published over 250 papers in
peer-reviewed journals and has taught and lectured
worldwide. In 1998 Dr. Datz received the Davisson-Germer
Prize, one of the highest honors bestowed by the
American Physical Society.
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