In the summer of 1906, Pohl completed his doctorate (Dr. Phil.) and took an assistantship in Berlin, working as instructor in the physics teaching labs under Heinrich Rubens, the Institute's director. He published joint articles with James Franck on ionic mobility in gases and on the propagation velocity of X-rays. From 1909 onward, he carried out research on the normal and the selective photoelectric effect in metals, and from 1910 he worked with Peter Pringsheim, on, among other things, the technically important problem of the fabrication of metal mirrors. In 1910, his monograph on the remote transmission of images appeared, and in 1912 he completed the "Habilitation". In an addendum, his "Habilitation" thesis contains a discussion of von Laue's discovery of X-ray diffraction.