Gerhard Herzberg, 1904-1999
Gerhard Herzberg, Nobel Laureate in Chemistry 1971, Distinguished Research Scientist at the National Research Council, and Past-President of the CAP (1956--57), died at his home in Ottawa on 3 March 1999 at the age of 94.
He was born on Christmas day in 1904 in Hamburg to a modest middle-class family, and was only ten when his father, who had suffered from chronic ill health, died. Herzberg attended the main Gymnasium in Hamburg with a scholarship, and was blessed with excellent teachers who instilled in him a love of astronomy, other branches of science, and mathematics. When it came time to think of university, he explored the possibility of studying astronomy but was advised that it would be impossible to make a living in this way. Instead he opted for a program in Engineering Physics at the Technical University in Darmstadt, and was fortunate to get a private scholarship which enabled him to attend. He studied under Hans Rau, carried out his first research on atomic hydrogen, and photographed an extensive series of Balmer lines, which is reproduced in countless texts to this day. His thesis on the spectrum of nitrogen and its afterglow earned him the Doctor of Engineering degree in 1928.
Herzberg spent the following two years as a postdoctoral fellow, first in Göttingen and then in Bristol. In Göttingen where the then-new quantum mechanics was being developed and was being used to explain problems in atomic and molecular physics, Herzberg worked with Walter Heitler in Max Born's Theoretical Physics Institute, and carried out experiments in the Institute of James Franck, who was a recent Nobel Laureate in physics (1925). There Herzberg met Luise Oettinger, a physics student in Franck's group, and they married in December 1929. He was asked by the students to give lectures on spectroscopy, and these formed the basis of his first book Atomic Spectra and Atomic Structure, still in print after 62 years. From the alternation of intensities in the rotational Raman spectrum of N2 Herzberg and Heitler concluded that the 14N nucleus has integer spin and follows Bose statistics. This was in 1929, three years before the discovery of the neutron, at a time when the 14N nucleus was thought to have an odd number of fermions (14 protons and 7 electrons) and so would have been expected to obey Fermi statistics. At this early stage of molecular orbital theory, Herzberg made an important contribution on bonding, non-bonding and anti-bonding electrons, and as a result was invited to Bristol by John E. Lennard-Jones (later Sir John), an early proponent of the theory. He also set up a spectroscopy laboratory in Bristol and studied the spectra of several diatomic and polyatomic molecules.
He returned to Darmstadt in November 1930 as Privatdozent, and remained there for almost five years during which he established an important spectroscopy laboratory and supervised the research of several students and visitors. Among the latter was John Spinks from the University of Saskatchewan (later its president), who was to play a major role in bringing the Herzbergs to Canada. An early contribution (1933) was a seminal paper with Edward Teller on the theory of vibrational intensities in electronic transitions. Teller was one of the pioneers in the application of quantum mechanics to polyatomic molecules, and continued over many years to have fruitful exchanges of ideas with Herzberg. Unhappily, with the rise of Nazism the political situation in Germany became rapidly worse and, because Luise was Jewish, the Herzbergs were forced to consider leaving their native country.
A year-long search showed that research positions were scarce all over the world because of the Depression, and many were already filled by academic refugees. At age 30, and recognised as one of the world leaders in molecular spectroscopy, Herzberg faced the possiblity of unemployment. He wrote to Spinks to see if he could be of any help in finding a position in Toronto or at the National Research Council, but these efforts were unsuccessful. However, through Spinks, Walter Murray, the President of the University of Saskatchewan, offered Herzberg a Guest Professorship in Physics for two years, funded by the Carnegie Corporation. Herzberg accepted the appointment, arrived in mid-September 1935, and within three months was given a permanent appointment. The Herzbergs spent ten happy years in Saskatoon, and raised their two children, Paul born in 1936 and Agnes in 1938.
During this time, Herzberg carried out important research projects on molecules of astrophysical interest, one in particular being the identification of three unknown spectral lines as due to CH+ by reproducing the spectrum in the laboratory with one of his students, Alex E. Douglas. This was the first interstellar molecular ion, and one of only three known interstellar molecules to be identified at that time. He was also able to show that the lengths of specific types of bonds in molecules depend in the nature of the neighbouring bonds. He saw the publication in German and English of Atomic Spectra and Atomic Structure and the first volume of the series Molecular Spectra and Molecular Structure: Diatomic Molecules , with
translations by Spinks. The second volume, Infrared and Raman Spectra, was written in English and published near the end of his stay in Saskatoon.
However, opportunities for research in Saskatoon were limited, and in 1945 Herzberg accepted a position at the Yerkes Observatory of the University of Chicago at Williams Bay. Finally he was able to realize his early ambition to work in astrophysics, and he developed techniques to observe molecular spectra at path lengths long enough to simulate planetary atmospheres. He predicted and observed the absorption spectrum of H2 due to the quadrupole moment of the molecule, and years later this was seen on Jupiter, Saturn and Uranus. In addition, he completely revised his volume on Diatomic Molecules. He also formed a lifelong friendship with the astrophysicist Subrahmanyan Chandrasekhar, later Nobel Laureate in physics (1983). In the event, despite the congenial atmosphere and scientific success, the Herzbergs stayed only three years in Williams Bay. They had developed a strong affection for Canada and were anxious to return.
C.J. Mackenzie, President of NRC, and E.W.R. (Ned) Steacie, Director of the Division of Chemistry, were instrumental in persuading Herzberg to join NRC and to establish a spectroscopy laboratory in the Division of Physics. He arrived in August 1948 and within four months was named Director of the Division of Physics. Herzberg was joined by Alex Douglas, his best student from the University of Saskatchewan, shortly thereafter by Donald A. Ramsay, Hin Lew, and Cecil C. Costain, and then a little later by Boris P. Stoicheff, all with interests and expertise in different regions of the spectrum. This team remained together for more than a decade, and together they developed the Spectroscopy Laboratory which rapidly gained world renown and has remained in the forefront of the field ever since. Full advantage was taken of the Postdoctorate Fellowship (PDF) Program of NRC, which made it possible to attract the best recent graduates from all over the world to work in the laboratory.
The decades following his arrival in Ottawa were extremely productive not only for Herzberg but for the "lab" as a whole. This was due in no small measure to the infectious enthusiasm and hard work of Herzberg himself, who came to be known affectionately as GH. The atmosphere can best be described by quoting one of the PDFs:
It was also during this time that Herzberg wrote the third volume in the series on molecular spectroscopy, Electronic Spectra and Electronic Structure of Polyatomic Molecules (1966). He devoted Saturdays to this task, thus adding to his already punishing work schedule. It is probably fair to say that there was no one in the lab who could consistently beat him in to work in the morning or leave later at the end of the day. He was also, as always, pursuing his research interests where, amongst other things, techniques for observing the electronic spectra of unstable molecules and free radicals were being developed. Two of the radicals which he spent many years looking for were methyl (CH3) and methylene (CH2). Finally, after two decades, he found a spectrum which was clearly due to CH2. There were, of course, many other unstable species found in the lab during this time but it is clear that Herzberg was especially proud of this discovery which was partly responsible for the award of the Nobel Prize in Chemistry in 1971. The Prize Citation reads
and in his address Professor Stig Claesson said -- in part
In the years since 1971 it has been shown that the ground state of methylene is not quite linear, but has a wide interbond angle of about 134 .)
Herzberg was an extremely effective lecturer because he took great pains to be well prepared. He was therefore very much in demand. Inevitably the award of the Nobel Prize increased the number of invitations that he received and this put enormous pressure on his time, particularly as he always found it hard to say no to any request. Nevertheless he still found time to pursue his research interests and to write, completing The Spectra and Structures of Simple Free Radicals in 1971 and Constants of Diatomic Molecules (with Klaus-Peter Huber) in 1979.
Herzberg showed dogged determination in achieving his scientific goals. It has already been mentioned that the search for CH2 took place over two decades. That is not to say that he spent all his time in the search but he never lost sight of an objective that he considered worthwhile. It is worth mentioning here some other long-term interests of his.
Hydrogen, both atom and molecule, interested Herzberg from the very outset of his career. Significant effort was spent in the experimental determination of the Lamb shift of the hydrogen (and helium) atom. This work required the establishment of accurate wavelength standards in the far ultraviolet and the final result was in complete agreement with theoretical calculations. The determination of the dissociation energy of the diatomic hydrogen molecule also presented an enormous experimental challenge and it was only after using the highest resolution available that Herzberg finally obtained a result in accord with theory. It should be remembered in this context that it was by no means certain at the time that theoretical calculations could rival experimental accuracy even for as simple a system as the hydrogen molecule. More recently much work was done on the excited states of hydrogen including an accurate determination of the ionization potential. Herzberg was also very much interested in obtaining spectroscopic evidence for the H3+ molecular ion. In this he was not himself successful but the ion was found by Takeshi Oka who, at the time, was a member of his group. However, one outcome of the search for H3+ was the recognition of the spectrum of the neutral H3 molecule in an electrical discharge through H2, an amazingly late finding considering how much research had been done on such discharges. The H3 results are described in a series of papers starting in 1979. Astronomical spectroscopy continued to attract Herzberg and the diffuse interstellar bands (DIBs) fascinated him. Despite the long-held view of astronomers that these absorption bands seen against background stars are due to dust grains, Herzberg felt that they were more likely due to gas-phase molecules. In 1980 Alex Douglas proposed that long carbon chains could be responsible for the DIBs and this received support recently when John P.~Maier of Basel identified C7- as the carrier of five of the hundred or more known DIBs. While this observation supports Herzberg's view, there is no doubt that he would have been very happy to see a more complete resolution of the problem of the DIBs in his lifetime.
The esteem that the spectroscopic and scientific communities held Herzberg in was evident in the conferences held every five years in his honour. The first of these took place in 1969 to celebrate his 65th birthday. At this meeting, when most would be thinking of retirement, he was appointed Distinguished Research Scientist. In 1974 the formation of the Herzberg Institute of Astrophysics was announced in his honour. It provided a place where he would be able to continue his research for as long as he wished. The most recent conference was held in 1994 and Herzberg officially retired in early 1995, but he still came into the Sussex Drive building of NRC on a regular basis until failing health finally prevented him.
Outside his scientific interests Herzberg was fond of hiking, particularly with friends like Konrad Bleuler and Ernst Miescher, in the mountains near Saas-Fee in Switzerland. He also had a lifelong interest in music. He took lessons on the violin in his early days and, while in Saskatoon, treated himself to voice lessons. His rich bass-baritone voice became familiar to all who knew him well (as indeed did his booming laugh). CAP members were able to hear him sing at a concert held during the 1965 meeting in Vancouver. He continued to listen to music, especially opera, and until recently would often be seen at concerts given by the National Arts Centre Orchestra in Ottawa.
Herzberg regarded both the arts and the sciences as essential activities in a civilized society. He was an eloquent advocate for fundamental science, particularly as budgetary restraints focussed more and more -- too much in his estimation -- on the bottom line.
Herzberg's first wife Luise died suddenly in 1971, tragically a few months before the award of the Nobel Prize. He is survived by his second wife, Monika, his son Paul, and his daughter Agnes.
John W.C. Johns
"GH gave leadership and direction to all of us in the lab by his own inimitable example. He worked long hours. He was deeply immersed in his own exciting researches, and yet he found time each day to talk to us about our own work. To our surprise, he somehow managed to keep abreast of the voluminous scientific literature, and he arranged for a constant stream of scientists to visit the lab and to give seminars, and so keep us up to date on spectroscopic activities elsewhere. And, above all else, both GH and Douglas were always available, to keep us out of experimental pitfalls -- or once lost in them, to gently ease us out and to put us on the right track. There were occasions, however, when we would catch only the blur of GH's white lab coat as he raced up the steps to his office, and we would be reminded that other important matters, either a budget or a pressing administrative problem, also had to be settled. But seldom would such difficulties be allowed to intrude on the daily progress of the lab."
"For his contributions to the knowledge of electronic structure and geometry of molecules, particularly free radicals."
"This year's Nobel Prize winner in Chemistry, Dr.~Gerhard Herzberg, is generally considered to be the world's foremost molecular spectroscopist and his large institute in Ottawa is the undisputed centre for such research. It is quite exceptional, in the field of science, that a single individual, however distinguished, in this way can be the leader of a whole area of research of general importance. A noted English chemist has also said that the only institutions that have previously played such a role were the Cavendish Laboratory in Cambridge and Bohr's institute in Copenhagen. . . . .
Herzberg had so far performed extensive precision determinations of the properties of over thirty free radicals among which are to be found the radicals methyl and methylene -- well known from organic chemistry. Among his exciting discoveries may be mentioned that radicals drastically change their shape with increasing energy. For example, methylene is linear in its ground state but bent in states of higher energy. Many of the most important results were only achieved after several years' work and some of the most exciting as late as the end of the 1960's. One can therefore note that this year's prize is truly an award for contributions of great current interest.''
Boris P. Stoicheff
James K.G. Watson