The Story of “The Nature of the Chemical Bond”: Coordinating Research & Funding

[Ed. Note: This year marks the 75th anniversary of Linus Pauling’s publication of his landmark text, The Nature of the Chemical Bond.  For the next six weeks we will take a detailed look at the creation, release and impact of a book that changed the scientific world.]

Linus Pauling’s The Nature of the Chemical Bond, first published in 1939, was the product of over two decades of diligence, sacrifice, and collaboration among a broad range of actors that included Pauling’s family, research assistants, professional colleagues and a variety of institutions. Pauling’s prefatory remarks to the book – “For a long time I have been planning to write a book on the structure of molecules and crystals and the nature of the chemical bond” – give an indication of the extent to which this was a long-term objective for Pauling, despite his being only 38 years old.

Looking back at his process, Pauling’s application for a grant from the Carnegie Institute in February 1932 provides a more detailed affirmation of his ambitions. In it, Pauling relayed how his undergraduate research in crystal structures at Oregon Agricultural College between 1917 and 1922 had laid the foundation for his current work by bringing him into contact with contemporary questions in structural chemistry. As a graduate student at Caltech, Pauling began to search for answers to those questions in the newly developing field of quantum mechanics.

In pursuit of those answers, Pauling and his wife Ava Helen, with the support of a Guggenheim Fellowship, left their one-year-old son, Linus Jr., with Ava Helen’s mother in Portland and traveled to Europe in 1926 to study quantum mechanics at its source. There, Pauling deepened his understanding and immersed himself even more by beginning to apply the new physics directly to chemical bonding.

J. Holmes Sturdivant

Upon returning to Caltech in 1927, Pauling began to seek funding so he could continue what he had begun. Let down by the National Research Fund, Pauling supported his work with funding from Caltech and the National Research Council, money which allowed him to hire a full time assistant, J. Holmes Sturdivant, who focused on x-ray crystallography and continued to work with Pauling for many years. Pauling also brought aboard Boris Podolsky for nine months to assist him with the more detailed technical components of connecting quantum mechanics to chemical bonding.

In 1932 Pauling expressed a hope that, with help from the Carnegie Institute, he could expand his work by funding more assistants and purchasing equipment like an “electric calculating machine,” a “specialized ionization spectrometer,” and a microphotometer. The Carnegie Institute was not interested. Luckily for Pauling, the Rockefeller Foundation came through with a general grant of $20,000 per year over two years, to be split between the physics and chemistry departments at Caltech. This allowed Pauling to keep Sturdivant on staff while adding George Wheland, Jack Sherman, and E. Bright Wilson, Jr. to his research team.

This scramble to secure funding and bring new people into the lab came amidst the publication of Pauling’s first four “Nature of the Chemical Bond” articles for the Journal of the American Chemical Society, proof positive that Pauling’s work was bearing fruit. Once the funding was secured and Sherman and Wheland began producing results, Pauling wrote – with Sherman and Wheland as co-authors – three more “Nature of the Chemical Bond” articles the following year, published in the newly established Journal of Chemical Physics. Wheland also worked with Pauling on a monograph discussing the application of quantum mechanics to organic molecules. Wheland finished his part of the book by 1937, but Pauling never got around to his portion: his desire to write a book length treatment of chemical bonds began, more and more, to take center stage.

Warren Weaver

In order to keep the funding coming in through the lean years of the Great Depression, Pauling was compelled to follow the lead of his patrons, the Rockefeller Foundation. Warren Weaver, Director of Natural Sciences for the foundation, told Pauling in December 1933 that the organization was “operating under severe restrictions” and that funding would go to projects “concentrated upon certain fields of fundamental quantitative biology.” That Pauling’s work had “developed to the point where it promises applications to the study of chlorophyll, haemoglobin and other substances of basic biological importance” was key to his potential receipt of continued dollars.

The commitment of Caltech’s chemistry department to continue pursuing the line of research suggested by Weaver helped Pauling to secure funding for the following year. A three-year commitment came after that, providing the Caltech group with a reliable source of support into 1938. Pauling thanked Weaver in February of that year for his direction, writing,

I am of course aware of the fact that our plans for organic chemistry not only have been developed with the aid of your continued advice but also are based on your initial suggestion and encouragement; and I can forsee that I shall be indebted to you also for the opportunity of carrying out on my own scientific work in the future to as great an extent as I have been during the past six years.

Secure funding allowed Pauling to maintain a research group consisting of graduate students and post-doctoral fellows. In his preface to The Nature of the Chemical Bond, Pauling expressed his gratitude to several of these individuals, including Sherman and Sturdivant. Another, Sidney Weinbaum, earned his doctorate under Pauling and continued on afterwards, helping Pauling with quantum mechanical calculations and molecular structures.

Fred Stitt worked as research fellow with Pauling and assisted him in teaching his graduate course on the applications of quantum mechanics to chemistry – an exercise, no doubt, that helped to shape Pauling’s own thoughts on the subject, crystallizing them in preparation for the book.

Charles Coryell and Linus Pauling, 1935.

Charles Coryell and Linus Pauling, 1935.

Charles Coryell worked as a research fellow at the Caltech lab with Pauling on the topic of magnetic susceptibilities, which were central to investigating chemical bonds.  (Coryell also later helped Pauling to construct a magnet for the Caltech labs, based on one already in place at Cornell.)

Edwin H. Buchman, according to a 1985 oral history interview, was self-supporting due to royalties from his synthesis of vitamin B1. Buchman told Pauling in May 1937 that he would assist Pauling “on any problem in which an organic chemist could be useful and for which extra space could be had.”

Once assembled, Pauling’s team helped him to refine his understanding of chemical structures and bonding as the time approached when he could produce a book-length treatment on the subject.

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Clarissa Lee, Resident Scholar

Clarissa Lee, January 2013.

Clarissa Lee, January 2013.

Clarissa Lee is the most recent alum of the Oregon State University Libraries Resident Scholar Program, having completed her stay in Corvallis in early January. Lee is a Ph.D. candidate in the Program in Literature at Duke University.

The focus of Lee’s research and writing is the notion of speculation in contemporary quantum theory; or, more generally, “speculative physics.”  While at OSU, Lee dug deeply into the History of Science rare book collection, the History of Atomic Energy Collection and the Ava Helen and Linus Pauling Papers in support of her dissertation.

Lee’s Resident Scholar presentation, “Experiments, Fictions, and the Question of Science-Modeling in Speculative Physics,” gave a glimpse into her ambitious research agenda as it is currently evolving.  From the abstract of her talk

In trying to work out what speculation entails, I have returned to the prehistory of particle physics, to earlier chains of physical epistemological developments in areas such as electricity, radioactivity and nuclear physics, especially in terms of their experimental-instrumental design and the formalistic developments that drive them forward….I will also explore the relationship of specific developments in particle physics to astrophysics and cosmology (with a nod towards the space science of the 1960s) especially over questions of space-time and locality of extra-terrestrial objects (as well as their relationship to String theory and hidden dimensions.)

According to Lee, her time at OSU

helped me shape…the arguments I am making about the freedom and constraints involved in physics speculation, especially through some of the physics problems faced by scientists in moving between theoretical prediction and experiment.

analog

Lee’s research “is also interested in theorizing and constructing models of fiction…through the use of speculative science fiction as well as speculative science fact, for the purpose of extending the imaginative realm of the scientific real.”

To this end, Lee made extensive use of Linus Pauling’s collection of Analog: Science Fact and Fiction paperback periodicals. Along with detective stories and the occasional walk, reading science fiction was Pauling’s favorite leisure activity, and his papers include thousands of dog-eared science fiction monthlies – a much-needed escape for Pauling from the unrelenting pressures that surrounded him for much of his life.

For Lee, sources like Pauling’s Analogs are useful in

trying to formulate some preliminary ideas concerning how fictionalizing can be used as a way for creatively modeling existing scientific ideas, theories and facts that aid scientists in pondering about more speculative areas of science, while also using scientific material to deal imaginatively with interdisciplinary studies of science and the humanities.

The Resident Scholar Program, now in it sixth year, offers research stipends of up to $2,500 in support of researchers wishing to make extensive use of materials held in the OSU Libraries Special Collections & Archives Research Center.  More information about the program, including the application form, is available here. The deadline for 2013 applicants is April 30th.

Polykarp Kusch (1911-1993)

Today marks the centenary of the birth of Polykarp Kusch, an accomplished physicist and Nobel laureate, born in Blankenburg, Germany on January 26, 1911.

In 1912, the Kusch family moved from Germany to the United States, where Polykarp would later build his reputation as a respected and successful scientist. After concluding his pre-college education in the Midwest, Kusch enrolled in the Case Institute of Technology (now the Case Western Reserve University) in Cleveland, Ohio. Although he initially planned to pursue a degree in chemistry, his interests quickly shifted toward physics, and he received his Bachelor of Science in the subject in 1931. Kusch continued his secondary education at the University of Illinois, where he earned both his Master of Science and Ph. D. in 1933 and 1937, respectively.

Upon completing his education, Kusch began a career in scientific research. He held his first position at the University of Minnesota, where he worked as a research assistant. There, he learned the technique of mass spectroscopy and garnered the support of his supervisors, which eventually led to his appointment as an instructor at Columbia University in New York City. At Columbia, Kusch worked in the lab of I.I. Rabi, and had the opportunity to take part in the magnetic resonance spectroscopy research that would later win Rabi the 1944 Nobel Prize in Physics. In 1941, Kusch left Columbia for a few years, during which time he researched and developed microwave generators and vacuum tubes for the Westinghouse Electric Corporation and the Bell Telephone Laboratories.

Around 1946, Kusch returned to Columbia, where he accepted a position as associate professor and conducted research in quantum mechanics. Specifically, he was most interested in the components of the atom – protons, neutrons, and electrons – and the ways in which they interacted with each other. This research would lead to his sharing of the 1955 Nobel Prize in Physics with Willis. E. Lamb. Kusch won his portion of the prize for “his precision determination of the magnetic moment of the electron,” a breakthrough that led to the development of a new field of physics called quantum electrodynamics, which describes how light and matter interact with one another.

In 1949, Kusch was promoted to full professor at Columbia; he would eventually become academic vice president and provost of the university.  In 1972 he decided to leave Columbia for the newly established University of Texas in Dallas, where he assumed a position as professor – he retained this role until his retirement in 1982. As Kusch’s career reached its later stages, he became more interested in societal issues, such as overpopulation and education, and the manners in which they could impact scientific progress. Besides the Nobel Prize, Kusch received many other awards, including the Illinois Achievement award in 1975. He was also a member of several important organizations, such as the National Academy of Sciences, the American Association for the Advancement of Science, and the American Philosophical Society.


There is little evidence in the Pauling Papers of extensive interaction between Kusch and Pauling.  Two sets of correspondence, however, suggest that the pair did share certain commonalities, and are indicative of the traits that, for better and for worse, tended to define Pauling’s professional life.

In the first instance, Kusch sent a telegram to Pauling dated November 7, 1960 indicating that one A. F. Forance had invited him to appear at an educational gathering but that, “in no event will I speak before his group.  I intend to send a letter of vigorous protest.”  It appears that Kusch’s note was sent in reaction to Forance’s having slighted Linus Pauling – an all too common occurrence for Pauling during this chapter in his life.

As it turns out, Pauling had been scheduled to deliver the principal address at the annual meeting of the Ohio Science Education Association in Columbus, and a second lecture to a smaller group in Cincinnati, both events organized by Mr. Forance.  Two days before the first lecture, Pauling learned from an Associated Press reporter that his Cincinnati appearance had been canceled, due to protests of Pauling’s politics (this was in the wake of Pauling’s SISS hearings) by a local American Legion group.  Pauling had received no official word from Forance however, and flew to Ohio as planned.  In his words

When I arrived in Cincinnati at 5 P.M. Mr. Forance and another teacher…met me at the airport.  We started on the auto trip to the city, and after perhaps fifteen minutes, Mr. Forance mentioned that the address for that night in Cincinnati had been canceled.

Pauling was understandably upset but chose to deliver his Columbus lecture as planned.  In responding to Kusch’s disgust-tinged telegram, Pauling counseled

We have to recognize that high school teachers and people in secondary education are quite vulnerable, and my own feelings about Mr. Forance have softened somewhat with the passage of time.

The second exchange between Kusch and Pauling, initiated some five months later, is indicative of their mutual scientific interests.  In it, Pauling comments on a paper that Kusch had recently co-published in the Journal of Chemical Physics.  Specifically, Pauling requests further information on the electronic magnetic moments, or lack thereof, in molecules of KFeCl3 and CsFeCl3. Pauling notes that “the matter is interesting to me because of the evidence that it provides about the iron-chloride bonds.”

Pauling to Kusch, March 30, 1961.

In providing the requested information, Kusch notes that “I am always delighted to have someone read my papers which generally describe an intense interest in a subject but not necessarily an interest of very many scientists in the subject matter.”  Indeed, this trait of intense interests in all manner of scientific topics shows up again and again in Pauling’s exchanges with his colleagues.  Coupled with an extraordinary work ethic, Pauling’s never-ending sense of wonder about the world was, as much as any other trait, the secret to his success.

Pauling Amidst the Titans of Quantum Mechanics: Europe, 1926

Erwin Schrödinger and Fritz London in Berlin, Germany, 1928.

[Ed. Note: Spring 2010 marks the seventy-fifth anniversary of the publication of Linus Pauling and E. Bright Wilson, Jr.’s landmark textbook, Introduction to Quantum Mechanics.  This is post 1 of 4 detailing the authoring and impact of Pauling and Wilson’s book.]

…the replacement of the old quantum theory by the quantum mechanics is not the overthrow of a dynasty through revolution, but rather the abdication of an old and feeble king in favor of his young and powerful son.

-Linus Pauling, “The Development of the Quantum Mechanics,” February 1929.

Since 1925 the John Simon Guggenheim Memorial Foundation has annually awarded fellowships to promising individuals identified as advanced professionals who have “already demonstrated exceptional capacity for productive scholarship or exceptional creative ability in the arts.”  The selection process is extremely competitive and recipients are generally esteemed in their chosen field as applicants face rigorous screening and are selected based on peer recommendation and expert review.

Since the first awards in 1925, many Nobel and Pulitzer prize winners have received Guggenheim Fellowships including, but not limited to, Ansel Adams, Aaron Copland, Martha Graham, Langston Hughes, Henry Kissinger, Paul Samuelson, Wendy Wasserstein, James Watson and, of course, Linus Pauling.

As one of the program’s earliest honorees, Pauling was awarded his first Guggenheim fellowship in 1926.  Heeding the advice of his mentors, Pauling had applied for the fellowship in hopes of pursuing an opportunity for international study.  Pauling’s advisers had long been insisting that he go to Europe to study alongside the leading experts in the budding field of quantum physics, and the Guggenheim funding provided Pauling with the opportunity to do just that.  It was this fellowship that allowed Pauling to travel abroad in order to learn from the European geniuses of quantum physics and to later become one of the early American pioneers of the new field of quantum mechanics.


Linus and Ava Helen Pauling’s apartment in Munich, Germany. 1927.

The subject of quantum mechanics constitutes the most recent step in the very old search for the general laws governing the motion of matter.

–Linus Pauling and E. Bright Wilson, Introduction to Quantum Mechanics, 1935.

The mid-1920s – the time during which Pauling was awarded the prestigious Guggenheim fellowship – was an exciting period to begin an exploration of quantum theory.  The tides were dramatically shifting in this field of study and the acceptance of the old quantum theory was rapidly declining.

Linus and Ava Helen left for Europe on March 4, 1926, arriving in Europe in the midst of what was a great quantum theory reform.  At the inception of quantum theory, physicists and chemists had attempted to apply the classical laws of physics to atomic particles in an effort to understand the motion of and interactions between nuclei and electrons.  This application was grossly flawed as the classical laws, such as Newton’s laws, were originally generated to represent macroscopic systems.   Theorists soon discovered that the classical laws did not apply to atomic systems, and that the microscopic world does not consistently align with experimental observations.

A series of breakthroughs by prominent theorists in the early- to mid-1920s accelerated the decline of the old quantum theory.  In 1924 Louis de Broglie discovered the wave-particle duality of matter, and in the process introduced the theory of wave mechanics.  Then in 1925, just one year before Pauling began his European adventure, Werner Heisenberg developed his uncertainty principle and thus began applying matrix mechanics to the quantum world.

In 1926, shortly after the Paulings arrived in Europe, Erwin Schrödinger combined de Broglie’s and Heisenberg’s findings, mathematically proving that the two approaches produce equivalent results.  Schrödinger then proceeded to develop an equation, now know as the Schrödinger Equation, that treats the electron as a wave.  (The Schrödinger Equation remains a central component of quantum mechanics today.)  The adoption of wave and matrix mechanics led to the development of a new quantum theory and the overwhelming acceptance of a burgeoning field known as quantum mechanics.


Arnold Sommerfeld and Ava Helen Pauling in Munich, Germany. 1927.

Where the old quantum theory was in disagreement with the experiment, the new mechanics ran hand-in-hand with nature and where the old quantum theory was silent, the new mechanics spoke the truth.

–Linus Pauling, February 1929

Pauling began his work in Munich at Arnold Sommerfeld‘s Institute for Theoretical Physics, a scholarly environment described by biographer Thomas Hager as “a new wave-mechanical universe for Pauling.”  It was this atmosphere that opened the door for Pauling to leave his mark as a pioneer of quantum mechanics.

In the fall of 1926, Pauling began applying the new quantum mechanics to the calculation of light refraction, diamagnetic susceptibility, and the atomic size of large, complex atoms.  Through these types of applications, Pauling developed his valence-bond theory, in the process making significant advancements in the new field of quantum mechanics and expanding our understanding of the chemical bond.

Two Years on the Pauling Beat

Today marks the second anniversary of the launching of the Pauling Blog.  In two years we have generated 214 posts, garnered over 63,000 views (not counting those accruing from syndication, which WordPress doesn’t include in its total statistics) and been graced with nearly 7,400 spam comments, most of which, thankfully, have been kept at bay by the good folks at Akismet.

We’re a bit less philosophical today than was the case one year ago, but we do want to take this moment to reflect back a bit.  Our readership has grown substantially over the past year and, as we enter our terrible twos, we figure this is a good opportunity to take another quick look at some writing that many of our readers may have never seen.  Here then, are ten worthwhile posts from the early days of the blog.

  1. Visiting Albert Schweitzer:  a review of the Paulings’ trip to Schweitzer’s medical compound in central Africa – in Linus Pauling’s estimation, “one of the most inaccessible areas of the world.”
  2. Pauling and the Presidents: the first in a series of three posts on Pauling’s relationship with this nation’s Commanders in Chief and with the office of the Presidency itself.  The other two posts focus on Pauling’s complicated interactions with John F. Kennedy, and with his own brief flirtation with the idea of running for the office himself.
  3. Pauling’s Rules: among Pauling’s major early contributions to science was his formation of a set of rules used to guide one’s analysis of x-ray diffraction data in the determination of crystal structures.
  4. The Guggenheim Trip: a three-part series detailing Linus and Ava Helen’s adventures as they toured through Europe for a year, meeting major scientific figures and absorbing the fledgling discipline of quantum mechanics.
  5. The Darlings: Maternal Ancestors of Linus Pauling:  an entertaining look at the colorful characters residing further down Pauling’s family tree.  We also featured Pauling’s paternal ancestry as well as Ava Helen’s lineage in separate posts.
  6. A Halloween Tale of Ice Cream and Ethanol:  Pauling’s typically detailed and ultra-rational recollection of a hallucination experienced late one November night.
  7. Clarifying Three Widespread Quotes:  three quotes attributed to Linus Pauling are scattered across the Internet.  This post investigates whether or not Pauling actually authored them.
  8. Pauling in the ROTC:  often accused of anti-Americanism due to his pacifist beliefs, few people know that Pauling actually served in the Reserve Officers Training Corps, ultimately rising to the rank of Major.  This post was among the first in our lengthy Oregon 150 series, celebrating Pauling’s relationship with his home state.
  9. Mastering Genetics: Pauling and Eugenics:  a post that delves into what was among the more controversial stances that Pauling ever took.
  10. Linus Pauling Baseball:  we can’t help it – the video is priceless.

As always, thanks for reading!

The Guggenheim Trip, Part III: Unexpected Colleagues

Walter Heitler, Fritz London, and Ava Helen Pauling in Europe. 1926.

Walter Heitler, Fritz London, and Ava Helen Pauling in Europe. 1926.

The paper of Heitler and London on H2 for the first time seemed to provide a basic understanding, which could be extended to other molecules. Linus Pauling at the California Institute of Technology in Pasadena soon used the valence bond method. . . . As a master salesman and showman, Linus persuaded chemists all over the world to think of typical molecular structures in terms of the valence bond method.” – Robert Mulliken. Life of a Scientist, pp. 60-61. 1989.

After Linus Pauling’s publication of “The Theoretical Prediction of the Physical Properties of Many-Electron Atoms and Ions,” he was ready for an even greater challenge – the problem of the chemical bond was a tantalizing enigma for Pauling, and he wanted more time in Europe to work on it. In the winter of 1926, he applied for an extension of his Guggenheim fellowship and with the help of a particularly complementary cover letter from Arnold Sommerfeld, Pauling was granted six more months of support.

Boosted by this news, he quickly began planning visits to Copenhagen and Zurich, both cities boasting of some of Europe’s finest research facilities. His first stop was Copenhagen, where he hoped to visit Niels Bohr’s institute and discuss ongoing research with the renowned scientist. Unfortunately, he had arrived uninvited and found it almost impossible to obtain a meeting with the physicist. Bohr, with the help of Werner Heisenberg and Erwin Schrödinger, was deeply engaged in research on the fundamentals of quantum mechanics, and was specifically attempting to root out the physical realities of the electron, in the process developing a theory which would eventually be termed the “Copenhagen Interpretation.”

Pauling did, however, did make one valuable discovery in Denmark — that of a young Dutch physicist named Samuel Goudsmit. The two men quickly became friends and began discussing the potential translation of Goudsmit’s doctoral thesis from German to English. Their work did eventually get them noticed by Bohr, who finally granted Pauling and Goudsmit an audience. Unfortunately for the pair, Bohr was neither engaging nor encouraging. Nevertheless, the two continued to work together, their cooperation eventually culminating in a 1930 text, The Structure of Line Spectra, the first book-form publication for either scientist.

In 1926 though, frustrated by his unproductive time in Copenhagen, Pauling departed, stopping briefly at Max Born’s institute in Göttingen before traveling to Zurich where other advances in quantum mechanics promised an interesting stay. Unfortunately, the man Pauling was most interested in, Erwin Schrödinger, proved to be just as unavailable as Bohr. The quantum mechanics revolution was consuming the time and thoughts of Europe’s leading physicists and Pauling, a small-fry American researcher, simply wasn’t important enough to attract the interest of men like Bohr and Schrödinger.

Fritz London

Fritz London

As a result, Pauling chose to converse and work with men of his own status in the scientific community. Fritz London and Walter Heitler, acquaintances of the Paulings, had spent the past several months working on the application of wave mechanics to the study of electron-pair bonding.

Heitler and London’s work was an outgrowth of their interest in the applications and derivations of Heisenberg’s theory of resonance, which suggested that electrons are exchanged between atoms as a result of electronic attraction. Heitler and London determined that this process, under certain conditions, could result in the creation of electron bonds by cancelling out electrostatic repulsion via the energy from electron transfer. Their work on hydrogen bonds likewise agreed with existing theories, including Wolfgang Pauli’s exclusion principle and G.N. Lewis’ shared electron bond. The Heitler-London model was well on its way to contributing to a new truth about the physics of the atom

Walter Heitler

Walter Heitler

Pauling used his time in Zurich to experiment with the Heitler-London work. While he didn’t produce a paper during his stay, the new model made a great impression on him and he returned to Caltech with a renewed sense of purpose. He was preparing to tackle the problem of atomic structure, in all its manifestations, and make history as one of the greatest minds of the twentieth century.

For more information, view our post “Linus Pauling and the Birth of Quantum Mechanics” or visit the website “Linus Pauling and the Nature of the Chemical Bond: A Documentary History.”

The Guggenheim Trip, Part II: The Growth of a Scientist

Linus Pauling, Werner Kuhn, and Wolfgang Pauli traveling by boat in Europe. 1926.

Linus Pauling, Werner Kuhn, and Wolfgang Pauli traveling by boat in Europe. 1926.

My year in Munich was very productive. I not only got a very good grasp of quantum mechanics — by attending Sommerfeld’s lectures on the subject, as well as other lectures by him and other people in the University, and also by my own study of published papers — but in addition I was able to begin attacking many problems dealing with the nature of the chemical bond by applying quantum mechanics to these problems.”
– Linus Pauling. The Chemical Bond: Structure of Dynamics, Ahmed Zewail, ed. 1992.

After his and Ava Helen’s stay in Italy, Linus Pauling was itching to return to the lab. The couple arrived in Munich in the last week of April and the first item on Pauling’s agenda was a meeting with Arnold Sommerfeld.

Sommerfeld, in association with Niels Bohr, was responsible for the Bohr-Sommerfeld model of the atom, a precursor to modern quantum mechanical ideas on atomic structure. At the time of Pauling’s European trip, Sommerfeld was serving as the director of the Institute of Theoretical Physics in Munich. He had spent the past decade building Germany’s community of physicists, nuturing many of Europe’s best scientists on a steady diet of cutting edge research. His lectures, famous by the time Pauling reached Europe, were known for their new and innovative content. As Thomas Hager, a Pauling biographer, explains, “[Sommerfeld] knew everyone in theoretical physics, had collaborated with many of them and corresponded regularly with the rest.” He knew exactly what was happening in his field and made sure his students did too.

Pauling’s first Munich meeting with Sommerfeld was something of a disappointment for the young scientist. Rather than being allowed to continue the work he had begun at Caltech, Sommerfeld chose to assign Pauling mathematical research relating to electron spin – an area that held little interest for him.

After a spell of half-hearted devotion to the electron spin problem, Pauling convinced Sommerfeld to allow him to study the motion of polar molecules. Pauling believed he could clarify portions of the Bohr-Sommerfeld model by introducing the effects of a magnetic field to the existing equations. This caught Sommerfeld’s attention and Pauling was subsequently instructed to continue his research under the stipulation that he provide Sommerfeld with the details of his work for presentation at an upcoming conference in Zurich. Pauling did so, and a few days after Sommerfeld had departed for the conference, he received an order to appear in Zurich to discuss his work.

Once at the conference, Pauling found himself surrounded by the leading physicists of Europe. Wolfgang Pauli, a young German physicist famous for his development of the revolutionary Pauli Exclusion Principle, was among those in attendance. On a whim, Pauling approached his colleague and began explaining his recent work on the Bohr-Sommerfeld model. Pauli was unimpressed. The paradox-riddled Bohr-Sommerfeld model, and Pauling’s work supporting it, was on its way out with the new ideas of quantum mechanics soon to take its place. Pauling’s research was too late to be of any value and Pauli was not shy about telling him so.

After finishing his summer vacationing with Ava Helen in Switzerland, Pauling returned to Munich for the fall semester. It was at this time that Pauling really began to prove himself, developing a reputation for his extensive knowledge and concentrated enthusiasm. Pauling’s most important accomplishment, however, was not his ability to make friends. Instead, it was gaining both the attention and the esteem of Arnold Sommerfeld. Pauling did so by discovering a mathematical error in the work of Gregor Wentzel, a protégé of Sommerfeld. The discovery and correction of this mistake garnered Pauling a great deal of respect in Sommerfeld’s eyes.

As it turned out, Pauling’s discovery of Wentzel’s error resulted in more than just Sommerfeld’s acclaim. It allowed Pauling to apply Wentzel’s work to the calculation of energy levels, which in turn provided the platform for a series of calculations on the energy values for complex atoms. This was a totally new approach to deriving atomic properties and Pauling took full advantage of his discovery, publishing his findings in a paper titled “The Theoretical Prediction of the Physical Properties of many-Electron Atoms and Ions.”

In a matter of months, Pauling had evolved from a star-struck young American to a legitimate player in the European field of quantum mechanics. Fortunately for him, his rise to scientific prominence had only just begun.

Read about Arnold Sommerfeld in “The Duelist” or learn more about this entire story on the website “Linus Pauling and the Nature of the Chemical Bond: A Documentary History.”