The loss of Oppenheimer left Pauling without help in his quest to make mathematical sense of the tetrahedral bonds of carbon. He needed to find a set of shortcuts, approximations of terms in the wave equation, that would simplify the mathematics enough to allow progress without distorting the results too much. Through 1929 Pauling tried again and again to batter through the mathematics, but nothing worked.

So he decided to return to Europe, visit old friends in Munich, tour crystallography laboratories and get some advice on the carbon problem. He and Ava Helen landed in England in May 1930 with five-year-old Linus junior in tow. After visiting several British laboratories they went on to Germany, where Pauling had a pleasant time visiting friends and catching up on the latest developments. He settled down for almost three months of work in Munich, working steadily on the application of the wave equation to the chemical bond, getting some help from Sommerfeld, but not succeeding in making a major advance.