Pauling first met the magnetic, brilliant American scientist J. Robert Oppenheimer in 1928 when they were both on postgraduate fellowships in Munich. By 1929, Oppenheimer, one of the new generation of quantum physicists, was teaching at both Caltech and at Berkeley.

He made an immediate impression in Pasadena. Thin, almost frail in appearance, with strikingly large, wide-set eyes and a head of thick, dark hair, he was attractive as well as brilliant. Although raised in New York, he seemed exotically European, Bohemian, poetic, chain-smoking, prone to obscure references to literature and philosophy. His only shortcoming seemed to be that he was a dismal lecturer, mumbling, scattering cigarette ashes, talking over the heads of his listeners, and packing the blackboard with barely readable, cramped equations. Despite that, he soon attracted a devoted band of acolytes, some of the West Coast's finest students, who were able to cut through the obscurity to the essentials of the new physics and who began following him on his annual trek between Pasadena and Berkeley. Oppenheimer was pursued, too, by scandalous rumors, hints of free love — perhaps even homosexuality — and radically leftist politics.

Linus and Ava Helen Pauling found him witty, interesting, and a welcome antidote to the deadly dullness of most of the Caltech faculty. Oppenheimer and the Paulings were soon sharing dinners and jokes, talking about European physics, and gossiping about Caltech and Berkeley professors. Oppenheimer came to Pauling for advice on how to become a better lecturer, and Pauling sought him out to talk about quantum mechanics. The two of them began to consider mounting a joint attack on the chemical bond, with Oppenheimer working on the mathematics and Pauling providing the chemistry background.

They became rather close rather quickly. Oppenheimer not only adopted some of Pauling's lecturing style; he began wearing an old fedora around campus, much like one that Pauling wore. He started to give Pauling gifts, sometimes little ones, a favorite ring on one occasion, and on another, a magnificently extravagant one, Oppenheimer's large boyhood mineral collection, the crystal treasury that had first spurred Oppenheimer's interest in science. It consisted of a thousand fine specimens, including some extraordinary calcites in which Pauling took special interest. Then there were the poems Oppenheimer gave Pauling, verses that Pauling found both obscure and troubling, mixing classical allusions with lines about mineralogy, Dante, and pederasty. Pauling, raised by his Mother in a boardinghouse in Portland, Oregon, had never had a friendship like this.

Neither had Ava Helen. She enjoyed Oppenheimer enormously, took pleasure in talking with him and flirting a little with him, as she did with almost everybody on social occasions. Perhaps she flirted a little more than usual, for Oppenheimer was unusually intriguing. Perhaps he felt her interest went beyond a casual friendship. It all went a little too far, in any case, when Oppenheimer came to her one day in 1929 when Pauling was at work and blurted out a clumsy invitation to join him on a tryst to Mexico. Surprised and flattered, Ava Helen told him no, of course not, she was married and took it seriously. That night, she reported the whole thing to Pauling. "I think she was somewhat pleased with herself as a femme fatale," Pauling said. Seeing how pleased she was, Pauling immediately cut off his relationship with Oppenheimer, ending any chance of collaboration on the chemical bond and leading to a coolness between the two men that would last for the rest of their lives.

Years later, Ava Helen told her husband, "You know, I don't think Oppenheimer was in love with me. I think he was in love with you." After mulling in over, Pauling concluded that she might be right.