Johannes Stark The Nobel Prize in Physics 1919

biography

The response of an intervalence band to an applied electric field, called an intervalence band Stark effect, is considered in detail.

Because the application of an electric field to a symmetric mixed-valence complex will break its symmetry in a way that depends on the strength of the field and the orientation of the complex in the field, it is necessary to identify the most general treatment of the asymmetric vibronic coupling problem for the calculation of intervalence band Stark effects.

For this reason three previous treatments of the asymmetric vibronic coupling problem are reviewed.

Each treatment is found to be less appropriate for the calculation of intervalence band Stark effects than a fourth that we introduce. It is also shown that a common choice of vibrational basis in these treatments can lead to inaccurate calculations for some mixed-valence complexes; an alternative is recommended.

Particular attention is paid to the effects of the field on the line shapes of intervalence bands and the sites of charge localization in mixed-valence complexes; both effects of the field lead us to identify intervalence band Stark effects as examples of a broader class of nonclassical Stark effects. A wide range of behavior for intervalence band Stark effects is predicted for isotropic samples. The Franck-Condon principle is utilized to develop a qualitative understanding of this behavior. Two methods of analysis are developed for determining the values of the vibronic coupling parameters that characterize a mixed-valence complex in the absence of the field from intervalence band Stark effects measured for isotropic samples; one of these methods can yield a complete description of the vibronic coupling parameters from an intervalence band Stark effect when the dipole strength of the intervalence band is either poorly characterized or poorly understood. The Stark effects of phase-phonon bands are also discussed. A graded description of charge localization in mixed-valence complexes is emphasized throughout this work, and a simple criterion for identifying the localized-to-delocalized transition is proposed.

Johannes Stark was born on April 15, 1874 in Schickenhof, Bavaria; his father was a landed proprietor. He was educated at the Gymnasium (grammar school) in Bayreuth and later in Regensburg and proceeded to Munich University in 1894 to read physics, mathematics, chemistry and crystallography. Stark graduated in 1897 on the basis of his doctoral dissertation on Newton's electrochronic rings in a certain type of dim media. He worked as assistant to von Lommel at the Physics Institute at Munich University from 1897 until 1900 and then became unsalaried university lecturer of physics at the University of G?ttingen. In 1906 he was appointed extraordinary professor at the Technische Hochschule in Hannover and in 1909 he followed the invitation of the Technische Hochschule in Aachen to become Professor there. A similar appointment at the University of Greifswald followed in 1917. Three years later he moved to the Physics Institute of the University of W?rzburg, where he stayed until 1922. Stark's scientific works cover three large fields: the electric currents in gases, spectroscopic analysis, and chemical valency. His spectroscopic work deals with the connection between the alteration in the structure and in the spectrum of chemical atoms. In 1919 Stark was awarded the Nobel Prize for Physics for his "discovery of the Doppler effect in canal rays and the splitting of spectral lines in electric fields". The prize enabled him to set up his own private laboratory.

In 1933 Stark was elected President of the Physikalisch-Technische Reichsanstalt (Physico-Technical Institute) as successor to von Paschen, where he remained until his retirement in 1939. At the same time he held the post of President of the Deutsche Forschungsgemeinschaft (German Research Association).

Stark was a prolific writer and published more than 300 scientific papers. His book Die Elektrizit?t in Gasen (Electricity in gases) was published in 1902. This was followed by works on elementary radiation and electrical spectroscopic analysis of chemical atoms. In connection with his work on chemical valency he wrote a book Die Elektrizit?t im chemischen Atom (Electricity in the chemical atom). Stark founded the Jahrbuch der Radioaktivit?t und Elektronik (The Year Book of Radioactivity and Electronics) and edited this publication from 1904 until 1913. Johannes Stark was a corresponding member of the Academies in G?ttingen, Rome, Leyden, Vienna and Calcutta, and was awarded the Baumgartner Prize of the Vienna Academy of Sciences in 1910 and the Vahlbruch Prize of the G?ttingen Academy of Sciences in 1914, and also the Matteucci Medal of the Rome Academy. During the last years of his life Stark, in his private laboratory on his country estate Eppenstatt near Traunstein in Upper Bavaria, investigated the effect of light deflection in an unhomogeneous electric field.

He was married to Luise Uepler. They had five children. His recreations were forestry and cultivation of fruit trees. Stark died on June 21, 1957.

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