About...The mathematician and physicist Johannes Robert (Janne) Rydberg was born in Halmstad in 1854. After final exams from Halmstads Högre Läroverk, studies were commenced at Lund University (LU) in 1873. Rydberg became assistant in physics at LU already in 1876, although his interest in mathematics dominated at this time. Rydberg's great talent in mathematics resulted 1879 in a PhD on the construction of conical sections. After a second thesis on functional analyses in 1880, Rydberg was appointed associate professor of mathematics.
His work...Rydberg's first article in physics was given the title: Studies on friction electricity, a study that qualified him as associate professor of physics at LU in 1882. His great interest in mathematics and regularities was most useful in his studies of the periodic table of the elements. Pioneering work carried out by Mendelejev showed a remarkable periodicity in the chemical and physical properties of the elements when arranging them after increasing atomic weight. The connection between spectra and chemical properties had previously been experimentally studied by Meyer, Kirchhoff and Bunsen. A theoretical explanation for these experimental findings was, however, not found. Rydberg pointed out that the periodic table of the elements clearly indicated that inter-atomic forces varied periodically with the atomic weight, and that many chemical and physical properties are consequences of periodic motion of the atoms. Furthermore, he argued that spectral analyses was the best tool for studying the mechanics of the atoms and, hence, the best tool for unraveling the physics behind the periodic table of the elements. It was not until 1920´s that it was clarified that similarities in chemical and physical properties of the elements rather reflect similarities in the valence shell of the atoms.
Due to the ever-increasing sophistication of experimental tools, accurate spectra were already accessible for many elements. The presence of line spectra had previously been noticed by Liveing och Dewar.
In the famous article "On the structure of line spectra of the chemical elements" from 1890, Rydberg could describe all known spectral series with the formula:
Here is the wave number (reciprocal wavelength), R the so called Rydberg constant and m and n are integers with n>m. Of these integers m has a definite value, while n is varying. The numbers a and b are known as quantum defects. It should be mentioned that Balmer a few years before had discovered a mathematical expression that described the spectral lines of hydrogen. This expression is a special case of the Rydberg formula given above with m=2 and a=b=0.
In spite of the fact that Rydberg never found a deeper explanation for his formula (Niels Bohr did), his contributions to modern physics can hardly be overestimated. For this reason Rydberg is often referred to as the father of modern atomic spectroscopy. Rydberg was appointed professor of physics at Lund University in 1901, a position that he kept until his death in 1919.