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Richard
R. Ernst – Autobiography
I
was born 1933 in Winterthur, Switzerland, where our ancestors resided at least
since the 15th century. We lived in a home built in 1898 by my grandfather, a
merchant. My father, Robert Ernst, was teaching as an architect at the
technical high school of our city. I had the great luck to grow up, together
with two sisters, in a town that combined in a unique way artistic and
industrious activities. Invaluable art collections and a small but first rank
symphony orchestra carry the fame of Winterthur far across the borders of
Switzerland. On the other hand, industries producing heavy machinery, like
Diesel motors and railway engines, provided the commercial basis of prosperity.
I
soon became interested in both sides. Playing the violoncello brought me into
numerous chamber and church music ensembles, and stimulated my interest in
musical composition that I tried extensively while in high school. At the age
of 13, I found in the attic a case filled with chemicals, remainders of an
uncle who died in 1923 and was, as a metallurgical engineer, interested in
chemistry and photography. I became almost immediately fascinated by the
possibilities of trying out all conceivable reactions with them, some leading
to explosions, others to unbearable poisoning of the air in our house,
frightening my parents. However, I survived and started to read all chemistry
books that I could get a hand on, first some 19th century books from our home
library that did not provide much reliable information, and then I emptied the
rather extensive city library. Soon, I knew that I would become a chemist,
rather than a composer. I wanted to understand the secrets behind my chemical
experiments and behind the processes in nature.
Thus,
after finishing high school, I started with high expectations and enthusiasm to
study chemistry at the famous Swiss Federal Institute of Technology in Zurich
(ETH-Z). I was rapidly disappointed by the state of chemistry in the early fifties
as it was taught at ETH-Z; we students had to memorize incountable facts that
even the professors did not understand. A good memory not impeccable logic was
on demand. The physical chemistry lectures did not reveal much insight either,
they were limited just to classical thermodynamics. Thus, I had to continue,
similar as in high school, to gain some decent chemical knowledge by reading. A
book from which I learned a lot at that time was "Theoretical
Chemistry" by S. Glasstone. It revealed to me the fundamentals of quantum
mechanics, spectroscopy, statistical mechanics, and statistical thermodynamics,
subjects that were never even mentioned in lectures, except in a voluntary and
very excellent lecture course given by the young enthusiastic Professor Hans
H.Günthard who had studied chemistry and physics in parallel.
It
was clear to me, after my diploma as a "Diplomierter Ingenieur
Chemiker" and some extensive military service, I had to start a PhD thesis
in the laboratory of Professor Günthard. Fortunately, he accepted me and
associated me with a young most brilliant scientist Hans Primas, who never went
through any formal studies but nevertheless acquired rapidly whatever he needed
for his work that was then concerned with high resolution nuclear magnetic
resonance (NMR), a field in its infancy at that time. Much of his and also my
time was spent on designing and building advanced electronic equipment for
improved NMR spectrometers. In parallel, we developed the theoretical
background for the experiments we had in mind as well as for the optimum
performance of the instruments. Signal-to-noise ratio calculations and
optimizations were daily routine as NMR suffers from a disappointingly low
sensitivity that severely limits its applications. Hans Primas developed and
analyzed field modulation techniques, constructed a field frequency lock
system, and contributed a new design of shaped pole caps for the electromagnet
that was supposed to deliver an extremely homogeneous magnetic field. These
developments led to two types of spectrometers that were adopted by
Trüb-Täuber, a Swiss electronics company, and sold all over Europe. Later in
1965, Trüb-Täuber was dissolved, and the NMR spectroscopy section led to the
foundation of Spectrospin AG that is, together with Bruker Analytische
Messtechnik, nowadays the world leading producer of NMR spectrometers.
My
own work dealt with the construction of high sensitivity radio frequency
preamplifiers and in particular high sensitivity probe assemblies, initially
for a 25 MHz, later for a 75 MHz proton resonance spectrometer. On the
theoretical side, I was concerned with stochastic resonance. The goal set by
Hans Primas was the usage of random noise for the excitation of nuclear
magnetic resonance, following the famous concepts of Norbert Wiener for the
stochastic testing of non-linear systems. The theoretical treatment was based
on a Volterra functional expansion using orthogonal stochastic polynomials. I
tried in particular to design a scheme of homonuclear broadband decoupling to
simplify proton resonance spectra. By applying a stochastic sequence with a
shaped power spectral density that has a hole at the observation frequency, all
extraneous protons should be decoupled without perturbing the observed proton
spin. The theoretical diffculties were mainly concerned with the computation of
the response to nonwhite noise. Experiments were not attempted at that time, we
did not believe in the usefulness of the concept anyway, and I finished my
thesis in 1962 with a feeling like an artist balancing on a high rope without
any interested spectators.
I
thus decided to leave the university forever and tried to find an industrial
job in the United States. Among numerous offers, I decided for Varian
Associates in Palo Alto where famous scientists, like Weston A. Anderson, Ray
Freeman, Jim Hyde, Martin Packard, and Harry Weaver, were working
along
similar lines as we in Zürich but with a clear commercial goal in mind. This
attracted my interest, hoping to find some motivation for my own work. And
indeed, I was extremely lucky. Weston Anderson was on his way to invent Fourier
transform spectroscopy in order to improve the sensitivity of NMR by parallel
data acquisition. After his involvement in the development of a cute mechanical
device, the "wheel of fortune", to generate and detect several
frequencies in parallel, he proposed to me in 1964 to try a pulse excitation
experiment that indeed led to Fourier transform (FT) NMR as we know it today.
The first successful experiments were done in summer 1964 while Weston Anderson
was abroad on an extensive business trip. In this work I could take advantage
in an optimum way of my knowledge in system theory gained during my studies
with Primas and Günthard. The response to our invention was however meager. The
paper that described our achievements was rejected twice by the Journal of
Chemical Physics to be finally accepted and published in the Review of
Scientific Instruments. Varian also resisted to build a spectrometer that
incorporated the novel Fourier transform concept. It took many years before in
the competitive company Bruker Analytische Messtechnik Tony Keller and his
coworkers demonstrated in 1969 for the first time a commercial FT NMR
spectrometer to the great amazement of Varian that had the patent rights on the
invention.
Still
at Varian, I was further extending my earlier work on stochastic resonance with
the introduction of heteronuclear broadband decoupling by noise irradiation,
the "noise decoupling" that led to a rapid development in carbon-13
spectroscopy. It has been replaced later by the much more effcient multiple
pulse schemes of Malcolm H. Levitt and Ray Freeman using composite pulses.
Of
major importance for the success of more advanced experiments and measurement
techniques in NMR was the availability of small laboratory computers that could
be hooked up directly to the spectrometer. During my last years at Varian
(1966-68), we developed numerous computer applications in spectroscopy for
automated experiments and improved data processing.
In
1968 I returned, after an extensive trip through Asia, to Switzerland. A brief
visit to Nepal started my insatiable love for Asian art. My main interest is
directed towards Tibetan scroll paintings, the so-called thangkas, a unique and
most exciting form of religious art with its own strict rules and nevertheless
incorporating an incredible exuberance of creativity.
Back
in Switzerland, I had a chance to take over the lead of the NMR research group
at the Laboratorium für Physikalische Chemie of ETH-Z after Professor Primas
turned his interests more towards theoretical chemistry. Despite an initial
lack of suitable instrumentation, I continued to work on methodological
improvements of time-domain NMR with repetitive pulse experiments and Fourier
double resonance. In addition, we performed the first pulsed time-domain
chemically-induced dynamic nuclear polarization (CIDNP) experiments. We
developed at that time also stochastic resonance as an alternative to pulse FT
spectroscopy employing binary pseudo-random noise sequences for broadband
excitation, correlating input and output noise. Similar work was done
simultaneously by Prof. Reinhold Kaiser at the University of New Brunswick.
The
next fortunate event occurred in 1971 when my first graduate student, Thomas
Baumann, visited the Ampere Summer School in Basko Polje, Yugoslavia, where
Professor Jean Jeener proposed a simple two-pulse sequence that produces, after
two-dimensional Fourier transformation, a two-dimensional (2D) spectrum. In the
course of time, we recognized the importance and universality of his proposal.
In my group, Enrico Bartholdi performed at first some analytical calculations
to explore the features of 2D experiments. Finally in the summer of 1974, we
tried our first experiments in desperate need of results to be presented at the
VIth International Conference on Magnetic Resonance in Biological Systems,
Kandersteg, 1974.
At
the same time, it occurred to me that the 2D spectroscopy principle could also
be applied to NMR imaging, previously proposed by Paul Lauterbur. This led then
to the invention of Fourier imaging on which the at present most frequently
used spin-warp imaging technique relies. First experiments were done by Anil
Kumar and Dieter Welti.
From
then on, the development of multi-dimensional spectroscopy went very fast,
inside and outside of our research group. Prof. John S. Waugh extended it for
applications to solid state resonance, and the research group of Prof. Ray
Freeman, particularly Geoffrey Bodenhausen, contributed some of the first
heteronuclear experiments. We started 1976 an intense collaboration, lasting
for 10 years, with Professor Kurt Wüthrich of ETH-Z to develop applications of
2D spectroscopy in molecular biology. He and his research group have been
responsible for most essential innovations that enabled the determination of
the three-dimensional structure of biomolecules in solution.
During
the following years, a large number of ingenious coworkers, in particular
Geoffrey Bodenhausen, Lukas Braunschweiler, Christian Griesinger, Anil Kumar,
Malcolm H. Levitt, Slobodan Macura, Luciano Müller, Ole W. Sørensen, and
Alexander Wokaun, contributed numerous modifications of the basic 2D
spectroscopy concept, such as relay-type coherence transfer, multiple quantum
filtering, multiple quantum spectroscopy, total correlation spectroscopy,
exclusive correlation spectroscopy, accordion spectroscopy, spy experiments,
three-dimensional spectroscopy, and many more. In parallel, numerous other
research groups contributed an even larger number of innovative methods.
Besides
these activities in high resolution NMR, we always had a research program in
solid state NMR going aiming at methodological developments, such as improved
2D spectroscopy techniques and spin diffusion, and applications to particular
systems such as one-dimensional organic conductors, polymer blends, and
dynamics in hydrogen-bonded carboxylic acids in collaboration with Thomas
Baumann, Pablo Caravatti, Federico Graf, Max Linder, Beat H.Meier, Rolf Meyer,
Thierry Schaffhauser, Armin Stöckli, and Dieter Suter.
More
recently, I had also the pleasure to closely collaborate with Prof. Arthur
Schweiger, an extremely innovative EPR spectroscopist, in the development of
pulsed EPR and ENDOR techniques. This turned out to be a specially challenging
field due to the inherent experimental diffficulties and the many ways to
overcome the problems.
In
recent years, more and more of my time has become absorbed by administrative
work for the research council of ETH-Z of which I am presently the president. I
recognized that teaching and research institutions vitally depend on the
involvement of active scientists also in management functions.
Looking
back, I realize that I have been favored extraordinarily by external
circumstances, the proper place at the proper time in terms of my PhD thesis,
my first employment in the USA, hearing about Jean Jeener's idea, and in
particular having had incredibly brilliant coworkers. At last, I am extremely
grateful for the encouragement and for the occasional readjustment of my
standards of value by my wife Magdalena who stayed with me so far for more than
28 years despite all the problems of being married to a selfish work-addict
with an unpredictable temper. Magdalena has, without much input from my side,
educated our three children: Anna Magdalena (kindergarden teacher), Katharina
Elisabeth (elementary school teacher), and Hans-Martin Walter (still in high
school). I am not surprised that they show no intention to follow in my footsteps,
although if I had a second chance myself, I would certainly try to repeat my
present career.
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