page_title: Robert Wichard Pohl
section_title: Professorship in Göttingen
hierarchical_section_title: Robert Wichard Pohl / Professorship in Göttingen
caption_attribution_description: Deutsch: Sichtbarnachung links von n-Leitung (durch Elektronen, grün) und rechts von p-Leitung (durch Defekt-Elektronen, braun) in einem KJ-Kristall. Kathode (links) und Anode (rechts) sind in den Kristall eingeschmolzene Pt-Spitzen. R. Pohl, „Elektrizitätslehre“, von der 10. Aufl. (1944) an.
context_page_description: Robert Wichard Pohl was a German physicist at the University of Göttingen. Nevill Francis Mott described him as the "father of solid state physics".
context_section_description: In February 1916, Pohl received the offer of an associate professorship in Göttingen (as successor to Eduard Riecke), but due to the war, he was unable to accept the position until early 1919.  In his baggage for the move to Göttingen were more than 40 boxes with apparatus for his lectures.
  Because of the offer of a professorship at the Technical University of Stuttgart in September 1919, Pohl was promoted to Full Professor in Göttingen in December 1920 and became director of the 1st Physical Institute there.  In June, 1922, he was offered a position in Würzburg, which he also refused.  Thus, he was a participant in the Golden Age of physics in Göttingen during the 1920s as one of the three full professors there, along with James Franck (director of the 2nd Physical Institute) and the theoretician Max Born.
  On Christmas 1922, Pohl married Tussa Madelung, the sister of Erwin Madelung, who was a research assistant in Göttingen when Tussa moved there from Strasbourg with her family in May, 1920.  Robert and Tussa had three children: Ottilie, Eleonore und Robert Otto, later physics professor at Cornell University.
  
   
  Photoelectric observations – however not from surfaces, as in Berlin, but rather in bulk insulators – were started by Pohl together with his assistant Bernhard Gudden in 1919. (The research work from this period was described in detail in .)  They discovered that diamond crystals become electrically conducting after irradiation with light.  Later, they observed the same effect in the alkali halide sodium chloride; however only after it had been colored as a result of X-ray irradiation.  Systematic observations of this coloration effect using artificially-prepared crystals  led to the discovery of color centers, which were investigated in detail in the following years.  By inserting three electrodes into a potassium bromide crystal, Pohl and Rudolf Hilsch were able to demonstrate the first model of a transistor based on color centers in 1938.
  Alongside this research work in his own institute, Pohl collaborated with his scientific colleagues in a variety of ways.  With the zoologist Alfred Kühn, he investigated the color perception of bees; for the chemist Adolf Windaus, he applied optical spectroscopy to the separation of Ergosterol from Cholesterol.  He helped the archeologist Kurt Müller to photograph antique vases without disturbing highlights.  He gave active support to his student Hans Joachim Pabst von Ohain when the latter began the first experiments on jet propulsion following completion of his doctoral thesis, in the Physics Institute but privately financed.
caption: n- and p-type conduction: visualization of n-type conduction (at left by electrons, green) and of p-type conduction (at the right by holes, brown) in a KI crystal. The cathode (at left) and the anode (right) are Pt needles which have been melted into the crystal.  From R.W. Pohl, Electromagnetism, from the 10th edition (1944) on.
exif: {"Image Orientation": "Horizontal (normal)", "Image XResolution": "2000", "Image YResolution": "2000", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop Elements 7.0 Windows", "Image DateTime": "2009:12:05 12:17:43", "Image ExifOffset": "172", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2709", "EXIF ExifImageLength": "1870"}