by Thomas Hager
Sommerfeld, like many physicists of the day, quickly appreciated the more classically recognizable ideas of wave mechanics and the relative simplicity and elegance of Schroedinger's mathematical approach compared to matrix mechanics—Schroedinger's system was more approachable, more "user friendly" than the austere matrices of Born and Heisenberg—although Sommerfeld doubted that wave mechanics actually described a physical reality. Every young natural scientist had studied the physics of waves in school, the idea of vibrating strings, for instance, and had a comfortable sense of what waves were all about. Even if electron waves didn't exist as such, Schroedinger's equations still translated into a visualizable image of an atomic nucleus surrounded by an electron "cloud" with a discernible shape. In hydrogen the cloud formed a ball of electricity in which the density decreased exponentially with distance from the nucleus. Wave mechanics also indicated that in more complex atoms additional electrons could be idealized as forming spherical shells in layers around the inner ball, as Bohr had predicted.
Many traditional physicists who had never liked quantum theory's revolutionary overtones greeted the wave picture eagerly as a substantiation of traditional physics. Pauling was not old enough to be a traditionalist, but he followed Sommerfeld's lead and employed wave mechanics as a more easily used, visualizable tool. As Pauling wrote to a colleague in 1926, "I find his [Schroedinger's] methods much simpler than matrix calculation; and the fundamental ideas more satisfactory, for there is at least a trace of physical picture behind the mathematics." Compared to matrix mechanics, the wave picture of the atom was, Pauling said, "anschaulich [clear] enough to appeal to me."
As with any promising new idea in physics, Sommerfeld made sure that wave mechanics was presented in Munich as quickly as possible. Pauling attended a seminar during his first semester that analyzed prepublication proof sheets of one of Schroedinger's early wave-mechanics papers. Everyone who was anyone in the field came to visit Sommerfeld; Schroedinger himself arrived in Munich in the summer of 1926 to lecture on his ideas. Pauling was present when, at the end of the Austrian's lecture, a boyish-looking young man with a shock of light brown hair jumped to his feet in the back of the room. It was Heisenberg. Angered by the quick acceptance of Schroedinger's ideas and worried about the possibility that his matrix system would be pushed aside, he attacked Schroedinger directly, asking him how his electron-wave smears could ever explain quantized processes such as the photoelectric effect and blackbody radiation. Before Schroedinger could answer, the head of Munich's experimental physics institute, the august Nobel Prize winner Wilhelm Wien, called back angrily, "Young man, Professor Schroedinger will certainly take care of all these questions in due time. You must understand that we are now finished with all that nonsense about quantum jumps." Schroedinger added calmly that he was confident that eventually any problems would be cleared up by his methods.
It was a clash of two worldviews. Heisenberg was increasingly convinced that the atom was, in a basic sense, unknowable, that reality at the atomic level had little to do with anything that could be pictured in the mind. Atomic reality was neither visualizable nor describable in classical terms; it could only be approached through his strange new matrix-based mathematics. Schroedinger was equally certain that the atom had to make some sort of classical physical sense. While the two were polite in their public debates, their private correspondence revealed the extent of their feelings. Schroedinger continued to term the idea of quantum jumps "something monstrous." Heisenberg called Schroedinger's insistence on a visualizable atom Mist (bullshit).
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Both the matrix and wave forms of the new quantum mechanics explained far more experimental results with fewer paradoxes than the old Bohr-Sommerfeld model of the atom—the basis of what would henceforth be called the "old quantum theory." Pauli was breaking the news to Pauling that his hard work on diatomic molecules was wasted because it propped up an outmoded system. "Not interesting" indeed.
Pauli also recognized that Pauling's crossed-field system offered a good test of the new quantum mechanics. Pauling had theorized that the old quantum theory predicted a measurable magnetic-field effect on the dielectric constant of hydrogen gas. That was probably wrong, Pauli told him; the new mechanics would most likely predict no effect. If Pauling could work out the new quantum-mechanical calculations for his system, he should be able to publish the same work he had thought would support the old quantum theory. Only this time he would help demolish it.
The final piece of the puzzle fell into place when Pauling heard from Pasadena that they couldn't find the magnetic effect he had predicted. For the next several weeks Pauling reworked his calculations using the new mechanics (he referred to both Heisenberg's and Schroedinger's forms). The results demonstrated, he said, "a remarkable failure of the old quantum theory and the success of the new." For Pauling, too, the old quantum theory was now dead.
"I am now working on the new quantum mechanics," he wrote Noyes two weeks after the Zurich congress, "for I think that atomic and molecular chemistry will require it." It soon became evident to Pauling, as to everyone else in physics, that the new system was a fundamental improvement. "Where the old quantum theory was in disagreement with the experiment, the new mechanics ran hand-in-hand with nature," Pauling was soon saying, "and where the old quantum theory was silent, the new mechanics spoke the truth."
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Ava Helen loved their time in Europe. She and Linus were having the honeymoon they had never had, and despite his arduous work schedule—he spent most evenings doing calculations in their room while Ava Helen read or practiced German—they still had time for fun. They went to the opera and visited the galleries in Munich; they often walked to the grand new Deutsches Museum, with its extensive scientific exhibits, took weekend mountain-climbing trips to the Alps, and sometimes went dancing at Odeon's Casino. "I love to dance with Linus for he is such a good dancer," Ava Helen wrote that summer. "We get along wonderfully well and do lots of little steps that other people can't do." And she was more than a social companion. The Paulings were invited several times to Sommerfeld's house, where Ava Helen made a favorable impression. When Sommerfeld learned that she played the piano, he had one of his own moved to the Paulings' apartment. As she had at Caltech, Ava Helen also accompanied Linus to lectures and seminars, even to the weekly cafe get-togethers where physicists talked shop. Often she was the only woman there. "One of the German boys said that including myself there are five Americans in the Institute for Theoretical Physics," she wrote proudly to Noyes that summer.
After a few months in Munich, the Paulings became fixtures in the small American student community. Together with the Guillemin brothers, a pair of U.S. postdoctoral fellows who lived in the same building as they, Linus and Ava Helen took on the role of unofficial welcoming committee for a number of visiting American students, introducing them to the city and the university, then heading to a favorite cafe to talk over the latest scientific findings (or more important matters, such as whether a fellowship stipend had come through).
Letters from Ava Helen’s mother helped them track Linus junior's health, happiness, and progress with walking. And although they missed him, both Ava Helen and Pauling were glad he wasn't along because of the extra work and inconvenience he would have caused. "My respect for my wife's good sense has been steadily rising," Pauling wrote Noyes after they had been in Munich some months, "for I argued strongly against leaving the baby."
The only dark period came at the beginning of July, when they received a letter from Pauling's sister Lucile with bad news about their mother. Belle's health had worsened dramatically, and she had been sent to a state hospital in Salem used primarily for treating the insane. "The news regarding Mamma has been a great shock to me," Pauling immediately wrote back. "I shall do everything I can, so just tell me what you want me to do. ... I have never known what to do, for I haven't ever learned the condition of affairs. ... I am sending all the money I can put together to Uncle Jim. If
more is needed I shall see about borrowing it. . . . See that Mamma has everything she needs."
By the time the letter reached Portland, Belle was dead.
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It was the end of an increasingly unhappy life. After Pauling had been at college for a year, Belle had married again. The groom was a tobacco-chewing soldier named Bryden whom she met on a blind date arranged by her sister Goldie. The courtship was short, and the match was doomed to failure. Pauling's sisters Pauline and Lucile both took an instant dislike to their new stepfather, who seemed to enjoy lying around the house more than working. Soon after their honeymoon Belle was hit by influenza and then developed pneumonia, both worsened by her chronic anemia. The newlyweds began quarreling. A few months after the marriage Bryden grabbed his hat and coat and said he was going to the barbershop. He never came back.
Pauline couldn't wait to leave, either. After graduating from high school, she followed in her brother's footsteps to OAC, with Linus's financial help, but she didn't like college life. She was pretty and young and eager to go someplace new. In 1925 she took a job as an assistant to the secretary in Portland's Elks Club and within a short time had attracted the admiration of the club's athletic director. Pauline encouraged him to look for opportunities in other towns, they married, and a few months later moved to Los Angeles. Belle collapsed when she learned that the couple had eloped.
Lucile, the youngest, most loving, least hardheaded of the three children, was left alone to look after her increasingly dependent mother. Belle's pernicious anemia was now entering a new phase, robbing her of movement and feeling in her legs, leading to bouts of irrationality and delusions. The pressure of making ends meet racked her nerves. Decisions had to be made about the boardinghouse, but Lucile, although she was in her early twenties, knew little about business and didn't like to make hard choices. "I left decisions, [Belle's] care, everything, up to others, being absolutely immature and irresponsible, and easily led," she later wrote Pauling.
The last time Pauling saw Belle, in March 1926 as he and Ava Helen came through Portland on their way to Europe, he recognized that his mother was incapable of caring for herself. Her hair had turned gray. She had trouble walking without help. But he would not interrupt his plans. He told her that he had deposited one thousand dollars in a Pasadena bank and that she was to tell him if she needed any of it; he also asked his uncle, Judge James Campbell, and a faithful longtime boarder, Mr. Ecklemann, to keep an eye on Belle.
Two weeks later, Belle sold her boardinghouse—at least on paper. The "buyer" was Lucile, the selling price ten dollars. Perhaps Belle wanted to avoid taxes or problems with an inheritance after her death; perhaps she wanted to reward the one child who had stayed with her. They then rented the house, and she and Lucile moved to a nearby apartment. It sapped the last of her energy. The delusions increased in frequency. She couldn't sleep. She was restless and fretful, one minute euphoric, the next suspicious and cynical. It was too much for Lucile, and Belle's older sister Goldie was called in to handle the situation.
There wasn't anything Goldie could do, either. The decision was made to commit Belle to the state hospital for the insane. After taking care of the legalities, Goldie rode with her sister sixty miles to the state hospital and, when they arrived, filled out the admittance questionnaire. Alcoholic drinks or drugs? "None." Natural disposition? "Moral character good. Disposition happy. Lost husband 16 years ago—raised family through great struggles." First symptoms of mental derangement? "Worried from illness and too much responsibility."
Lucile visited a few days later and was overpowered by the sight of her mother in a mental ward. In tears, she asked her Aunt Goldie to undo what had been done but was told it was too late.
Belle died a few weeks after she was admitted. She was forty-five years old.
Pauling read the news in a letter from his sister a few days later, while entertaining friends in his Munich apartment. He had heard a little about her deterioration in what he remembered as a "silly, abusive and unintelligible letter" from Goldie calling him to task for his failure to adequately support Belle, but her death still came as a shock. He broke down, crying in front of the group as Ava Helen tried to comfort him.
All of the guilt and worry Belle's children had stored up for years erupted after her death. Pauling’s sister Pauline sent him a scathing letter a few days later detailing the ways he had been too much of a skinflint to help Belle, noting that he was too cheap to even buy his wife decent clothes. Pauling responded carefully and coolly, noting how little he had heard about Belle's final deterioration, listing the money he had sent and outlining the arrangements he had made for Belle's care. Then, in a letter to Lucile, he let a bit of emotion show. "Perhaps you do not realize that you haven't let me know about things. I can, of course, never feel the same towards Pauline after the terrible things she said in her letter. Every one of her statements but one is a slanderous lie. The one true statement, that Ava Helen hasn't had the beautiful clothes Pauline has had, arises from the fact that Ava Helen was spending about as much per year for clothes as Pauline spent per month, in order that we might pay the interest and start paying off the money that sent Pauline to an unproductive year in Corvallis and the other money I gave Mamma. ... I have become rather accustomed to slander, and I know that people will always take Aunt Goldie's ravings with many grains of salt; but I hate to have you laboring under an illusion regarding me. ..."
It was impossible to return for the funeral, and there was little more that could be done from the other side of the world. "I can think of so many things that I intended doing some day," Pauling wrote Lucile just after Belle's death, "but now it is too late."
A Fine Figure
Pauling's remorse was leavened with relief. He and his mother had never understood each other well or loved each other enough; his relationship with Belle had been based largely on feelings of filial duty and guilt. That weight was now lifted. At the beginning of August, Pauling and Ava Helen left for a long-planned vacation in Switzerland and France, where he did some work and had a great deal of fun. When they returned to Munich in the fall, Pauling sported a new tailor-made suit and a Scottish woolen scarf. "He looks quite dashing, especially when he carries his Italian cane," Ava Helen wrote.
He cut a fine figure professionally as well. While some Europeans expected that visiting Americans would be bumpkins, relatively unprepared scientifically and uncultured in general, experiences during the 1920s with some of the more outstanding scientific specimens, including John Slater, Edward Condon, Harold Urey, Karl Compton (later president of the Massachusetts Institute of Technology), and Pauling, helped change the image. Pauling's command of German was adequate and getting better—within a few months of arriving he could lecture in it—and he was working very hard to understand the new physics. The German-born physicist Hans Bethe, finishing his doctoral work under Sommerfeld in 1927, remembered that compared to the average American, Pauling "certainly was very different. He was generally recognized as really knowledgeable." Tall, friendly, and enthusiastic, Pauling also fit the European stereotype of a Westerner, a sort of cowboy of science. "A young, lanky man who knew enormously much and was an excellent lecturer" was how Hermann Mark, a German researcher who met Pauling in Munich, remembered him at the time.
During Pauling's first semester in Munich he took a lecture class from Sommerfeld devoted to differential equations, a form of calculus essential to solving atomic problems. And as he listened, Pauling began absorbing Sommerfeld's swashbuckling mathematical approach to attacking the mysteries of the atom. The director practiced a practical, flexible style of mathematics in which finding equations that reflected and explained real-world experimental results—mathematics that worked—was more important than pure, formal rigor. He didn't worry too much about internal consistency; he used mathematical tricks. Rather than simply passing on old information or prescribing specific approaches to problems, he pointed out the holes in current theories and presented his
students with a toolbox of mathematical devices that could be used to create new theoretical structures. This was an ideal approach for a rapidly changing field like quantum physics. It appealed especially to Pauling, whose own use of mathematics would always be less rigorous than practical.
Even so, Pauling's mathematical skills were sharp enough to assure his reputation as an American whiz kid. He walked into Sommerfeld's office one day in the late summer of 1926 with a problem. It concerned one of Sommerfeld's assistants, Privatdocent Gregor Wentzel, who had earned his Ph.D. with Sommerfeld a few years before and whose theoretical work since then had established him as a rising star of physics. Wentzel wrote a paper that Pauling found while searching for anything available on the quantum mechanics of many-electron atoms. In going through the paper, titled "A Difficulty with the Theory of the Spinning Electron," Pauling found that the problem was not with spin but with Wentzel's mathematics. The privatdocent had made an error in calculation: "The difficulty vanished," Pauling said, "if you did the work correctly." Pauling reworked Wentzel's calculations and came out with values closer to those found experimentally. Sommerfeld took Pauling's work to Wentzel, and it was agreed that the American was right. Pauling wrote a short paper on his correction in somewhat clumsy German; Sommerfeld threw it out, had Pauling rewrite it in English, and then had an assistant translate that into German for publication in the Zeitschrift fur Physik. It marked a turning point in Pauling's use of quantum mechanics: He had learned to fashion the new physics into a tool that could help him explain the properties of atoms. It also marked a turning point in his relationship with Sommerfeld, who now understood that the young American was someone to take seriously.