Why did Linus Pauling study quantum mechanics in Germany?

Linus Pauling studied quantum mechanics in Germany after receiving a Guggenheim Fellowship to pursue this research in Europe. He spent the majority of his 18-month fellowship at the Institute for Theoretical Physics in Munich, working under the guidance of Arnold Sommerfeld.1

Pauling sought to utilize quantum mechanics as a theoretical tool to complement the experimental methods, such as X-ray diffraction, that he used to explore molecular structures. By applying these quantum mechanical principles, he was able to develop the valence bond theory and provide a deeper understanding of chemical bonding, which he later summarized in his influential book, The Nature of the Chemical Bond, and the Structure of Molecules and Crystals (1939).23