Gerhard Herzberg Physical Chemistry

Won the 1971 Nobel Prize in chemistry for using spectroscopy to discover the internal geometry and energy states in simple molecules, and in particular the structure and characteristics of free radicals.

"You shouldn’t do science just to improve wealth — do science for the sake of human culture and knowledge. There must be some purpose in life that is higher than just surviving."

The Story

Gerhard Herzberg bends over the piles of paper on his big desk. He is overwhelmed. As director of the Pure Physics Department at Canada’s National Research Council, the fall of 1959 is a very busy time for him. Jack Shoesmith, his research technician, comes into the sun-filled office and walks up to the tall windows overlooking the Ottawa River. He says, casually, “I have an interesting spectrum to show you.”

Herzberg thinks of all the meetings and conferences he has to organize, the paper he is writing, presentations he is preparing and the book he is trying to finish, the third volume of his series Molecular Spectra and Molecular Structure. “I don’t have time for this,” he thinks.

“It’s good,” says Jack.

Reluctantly, Herzberg gets up from his chair and follows the young technician down a flight of stairs to the lab below. It’s a big high-ceilinged room, dimly lit and smelling of ammonia and hot electric wiring. There’s a hint of ozone in the air, as before a thunderstorm. They walk past the special spectrograph that Shoesmith has built — a long steel tube about 50 centimetres high and 3 metres long. Vacuum hoses and electrical wires snake around the base of the apparatus, but the pumps and electricity have been turned off. The big room is quiet except for the murmurs of a small crowd that has gathered in the corner.

Herzberg hurries over to see what they are looking at. A long, thin strip of glass with a seemingly random pattern of vertical lines blackening its surface — a spectrogram — lies on a viewing screen. Recognizing it at once, Herzberg picks it up for a closer look. Instantly he shouts, “That’s it!” and breaks out laughing. “Eighteen years,” he thinks. “I’ve been looking for you for eighteen years.”

What Herzberg held that day was the first spectrogram of a simple chemical called methylene, a molecule consisting of a carbon atom with two hydrogen atoms, one on either side, written CH2. What was special about this? Methylene is a very unstable molecule, a free radical — a transition molecule created briefly in a chemical reaction when molecules come together and transform themselves into something new. Free radicals last only for the length of time it takes for their constituent atoms to rearrange themselves with other molecules into new molecules — a few millionths of a second — so it’s very difficult to obtain a spectrum of such fleeting entities. Herzberg was delighted because the spectrum of the CH2 free radical was a key to proving many outstanding theories concerning the internal structure and energy states of molecules. That particular spectrum that Herzberg identified in 1959 eventually resulted in his winning a Nobel Prize in 1971.

As a young scientist...

As a 12-year-old in Hamburg, Germany, Herzberg and a friend named Alfred Schulz constructed a homemade telescope. They patiently ground the glass lenses and set them in handmade mounts in a metal tube. On clear nights they used to take the streetcar to the city park and set up the telescope to look at the moon and planets.

In 1933, Herzberg was working as a lecturer at the university in Darmstadt, Germany, when the Nazis introduced a law banning men with Jewish wives from teaching at universities. Since Herzberg had married a Jewish woman in 1929 — Luise Oettinger, a spectroscopist who collaborated with Herzberg on some of his early experiments — he began making plans to leave Germany near the end of 1933. Earlier that year he had worked with a visiting physical chemist named John Spinks, from the University of Saskatchewan. Spinks helped Herzberg get a job at the university in Saskatoon. It was very difficult for German scientists to find work outside Germany; thousands of them were leaving to escape the Nazis and they were all looking for jobs at the same time. When Herzberg and his wife left Germany in 1935, the Nazis let them take only the equivalent of $2.50 each, as well as their personal belongings. Fortunately, before he left, Herzberg was able to buy some excellent German spectroscopic equipment to take with him to Saskatoon. At the time you couldn’t buy such equipment in Canada.

Leaving Germany was very painful for the Herzbergs and they had no idea what they would find in Saskatoon. But Saskatchewan turned out to be a good experience for them, although it was very different from Germany. During the 10 years they lived there, Herzberg taught physics and wrote his famous book Molecular Spectra. His children were born in Saskatoon.

After moving to Chicago for a few years, Herzberg accepted a position with Canada’s National Research Council in Ottawa and was director of physics there from 1949 to 1969. During this time he made his Nobel Prize-winning discoveries in molecular spectroscopy. He worked at the National Research Council as a distinguished research scientist until his death at the age of 94 on March 4, 1999.

The Science

Herzberg was a physicist, but his discoveries are important to chemists because they involve the internal geometry and energy states of molecules. Remember: When Herzberg was born, the concept of an electron was just catching on. When he graduated from university, people had yet to discover how atoms combined to form molecules. It was all new theory. Very little had been proven.

To try to prove all these exciting ideas, Herzberg became a pioneer in the field of molecular spectroscopy, the study of how atoms and molecules emit or absorb light. By analyzing spectrograms — a sort of photograph of the way a molecule emits and absorbs light — he was able to tell a lot about molecules. For example, by measuring the distance between the lines on a spectrogram and counting how many lines there were, he was able to apply some mathematical formulas that described the energy levels and probable locations of the electrons in the molecule. This was very useful to chemists, because the new knowledge helped them to imagine new ways to combine chemicals to create new substances.

Once the spectrum of a molecule is known, astronomers can also use it. They can characterize the composition of distant stars and nebulae by training spectrographs on them through telescopes. This is handy if you are interested in knowing what stars are made of. It’s a way to learn what is out there, millions of light years away, without having to make the impossibly long trip to visit a place and take samples. This is one thing that really interested Herzberg, because it tied in with his childhood love of astronomy.

A spectrogram is created with a machine called a spectrograph. It takes a beam of light created by burning the chemical you wish to investigate. The light is focused by a lens, then passed through a prism and spread out into its component parts, like a rainbow. But this rainbow is very precise and appears as dark and light vertical lines that you can measure.

A spectrogram is a long piece of plate glass coated with photographic chemicals. After they have been exposed in a spectrograph and developed, the plates have dark, vertical lines. By measuring the spacing and thickness of the lines, physicists can apply mathematical formulas and determine some of the energy states of the molecules whose light produced the spectrogram.

The distance between the larger lines in the spectrum is proportional to the molecule’s “vibrational” energy. The small groups of lines clustered around the major lines represent the “rotational” energy of the molecule. These lines and their mathematical relationships are called Balmer lines, for the Swiss high school teacher who figured them out in 1885.

Methylene (CH2) is a free radical, which means it has an extra pair of electrons that it tries to share with another molecule. These extra electrons make the free radical very reactive, meaning it will combine quickly, usually within a few millionths of a second, with some other molecule.

Mystery

Strange as it may seem, in his later years Herzberg liked to remind people that they should not do science for the purpose of doing something useful. “That’s not why I did it,” he said. “Scientists wonder how certain things work, so they try more and more to find out how and why. Whether or not their work will lead to something useful, they don’t care, because they don’t know, and for that matter, they’re not that interested. If you develop science only with the idea to do something useful, then your chances of discovering something useful are less than if you apply your mind to finding something essential.” According to Herzberg, a true scientist looks to uncover the mysteries of nature for the sole purpose of advancing human knowledge. The usefulness of this knowledge becomes self-evident after it is discovered. Prime examples of this are X-rays and lasers, both of which were discovered by physicists who had no idea how useful their discoveries would later become.

Explore Further

Gerhard Herzberg, Atomic Spectra and Atomic Structure, Dover, 1944.

J. Michael Hollas, Basic Atomic and Molecular Spectroscopy, Wiley-RSC, 2002.

Boris Stoicheff, Gerhard Herzberg: An Illustrious Life in Science, NRC Press, McGill-Queen’s University Press, 2003.

An introduction to spectroscopy on the NASA Goddard Space Flight Center website.

Career Advice

So You Want to Be a Physicist

When Herzberg finished high school at the age of 19, he dearly wanted to become an astronomer. At that time there was a vocational office in Hamburg where young people could go for career guidance. Herzberg went there and asked a counsellor, “How do I become an astronomer?” His request was sent all the way up to the director of the top observatory in Hamburg, but the answer was disappointing: he was told he would need to be independently wealthy to support himself as an astronomer. There was no way of making a living as an astronomer. Instead he was advised to go to university and study physics.

He still had no way to pay for a university education, but he wrote a letter to one of the biggest shipbuilding companies at the time, Hugo Stinnes Lines, and was lucky enough to get a scholarship. That was enough for him to live on while he attended university, launching him on a lifelong career as a physicist.

The Person

Birthdate
December 25, 1904
Birthplace
Hamburg, Germany
Date of Death
March 4, 1999
Place of Death
Ottawa, Ontario
Residence
Ottawa, Ontario
Family Members
  • Father: Albin H. Herzberg
  • Mother: Ella Biber
  • Children: Paul and Agnes
  • Spouse: Monika Tenthoff
Personality
Jovial, modest
Favorite Music
Mozart’s Quartet for Flute, Violin, Viola, and Cello
Other Interests
Singing, music, mountain hiking.
Title
Distinguished Research Scientist
Office
Herzberg Institute of Astrophysics, NRC, Ottawa
Status
Deceased
Degrees
  • Diplom Ingenieur, Darmstadt Institute of Technology, Germany 1927
  • PhD, Darmstadt Institute of Technology, Germany, 1928
  • Privatdozent (post Doctorate), University of Goettingen, Germany 1929
  • Honorary degrees from universities of Oxford, Cambridge and Chicago including many others
Awards
  • Medaille de L’Université de Liege, 1950
  • Henry Marshall Tory Medal, Royal Society of Canada, 1953
  • Joy Kissen Mookerjee Gold Medal, Indian Assn. for the Cultivation of Science, 1954
  • Gold Medal, Canadian Association of Physicists, 1957
  • Medal of the Society for Applied Spectroscopy, 1959
  • Medaille de l’Université de Liege (silver), 1960
  • Medaille de l’Université de Bruxelles, 1960
  • Pittsburgh Spectroscopy Award, Spectroscopy Society of Pittsburgh, 1962
  • Frederic Ives Medal, Optical Society of America, 1964
  • Willard Gibbs Medal, American Chemical Society, 1969
  • Gold Medal, Professional Institute of the Public Service of Canada, 1969
  • Faraday Medal, Chemical Society of London, 1970
  • Royal Medal, Royal Society of London, 1971
  • Linus Pauling Medal, American Chemical Society, 1971
  • Nobel Prize in Chemistry, Swedish Royal Academy of Sciences, 1971
  • Chemical Institute of Canada Medal, 1972
  • Madison Marshall Award, American Chemical Society (North Alabama Section), 1974
  • Earle K. Plyler prize, American Physical Socie
Mentor
Hans Rau, his thesis advisor at Darmstadt who inspired Herzberg to find his own problem to study, then supported his early studies of molecular spectroscopy and sent him to meet Schrödinger, the brilliant Viennese physicist.
Last Updated
March 10, 2011
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