Spain and the world of quantum physics (1920-1957): German and US physicists viewed through the correspondence of Miguel Catalan, discoverer of the multiplets

Full text: Miguel Catalan (1894-1957) was an spectroscopist who made the most important contribution to quantum physics produced by a Spanish scientist: the discovery of multiplets, while he was working in 1920-1921 with Alfred Fowler in London. Multiplets were immediately used by Arnold Sommerfeld, and this gave rise to a relationship between both scientists that included the Spaniard spending one year at Munich, and afterwards a collaborator of Sommerfeld, Karl Bechert, doing the same in Madrid. I will use the correspondence interchanged between Catalan and Bechert to show the latter opinions of his master, opinions that show Sommerfeld in a new light. A similar approach will be used by using letters that Catalan sent during the decades of 1930 and 1950 while he spent prolonged periods of time in the United States, mainly in Washington D. C. and Princeton. The comments made there offer a different view of the American physics community. (author)