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Janne Rydberg


Fysik och Skolteknik

Janne Rydberg (1854-1919)

[Youth] [Getting established] [Atomic spectra] [Fight for tenure] [Final years] [Sources]

Youth in Halmstad

Johan Robert (Janne) Rydberg was born on 8 November 1854 in Halmstad. His father Sven, a local merchant and minor ship owner in this port town on the west coast of Sweden, died when Janne was only four years old. At age 10, he enrolled in Halmstad's högre läroverk. In his final examinations in 1873 he took Swedish, Latin, Greek and Hebrew, French, German and English, Religion and Philosophy, History and Geography, Natural History, and Mathematics and Physics, all with high marks.

Getting established in Lund

His good grades gained him admittance to Lund University in the autumn of 1873. Rydberg received his filosofie kandidat in 1875. In 1879 he received his filosofie licentiat on a thesis on the construction of conic sections. After a thesis on algebraic integrals and functions he was appointed docent in mathematics in 1881. But already in 1876, Rydberg had been appointed amanuens (teaching assistant) at the physics institute. After publishing an experimental study on friction electricity, he was appointed docent on physics in 1892.
In 1886, Rydberg married Lydia Eleonora Matilda Carlsson, the daughter of a medical official, and the couple had two daughters and a son.

Ordering atomic spectra

Driven by his desire to understand the periodic system of the elements, Rydberg set out to find order in the the enormous amount of data of atomic spectra. Their main use had been to provide fingersprints for chemical analysis of minerals and of stars. Guided by the prior work of Liveing and Dewar, Rydberg could discriminate among "sharp" and "diffuse" series. Rydberg was the first to relate the "principal" lines into a distinct series.
In order to minimize the number of calculations, he decided to introduce the wavenumber n, which is the reciprocal of the wavelength. The wavenumber expresses the number of waves per centimeter. Having made this change, he began to see patterns not previously discernable. He found that when he plotted for a given series, the difference in wavenumber versus the ordinal number of the term m, he obtained hyperbolic-shaped curves that were virually identical in shape for different series and different elements.
First he tried the formula

n = no − Co/(m+m'),

where no is the series limit when the ordinal number m approaches infinity, and Co is a constant and m' is a constant depending on the particular series. This formula did not work very well, and it did not give the same Co for all series.
He was just trying the formula

n = no − No/(m+m')2,

when he saw Balmer's formula for the hydrogen spectrum

λ = hm2/(m2 − 4),

which he rewrote as

n = no − 4no/m2.

This shows that hydrogen is a special case with m'=0 and No=4no. No is a universal constant common to all elements. Now this constant is known as the Rydberg constant, and m' is known as the quantum defect. Rydberg noted that m' is approximately the same different "diffuse" or different "sharp" series, but that diffuse and sharp series of the same order have essentially the same value of no.
Between the principal and the sharp series of lithium, sodium, and potassium, there is a special relationship:

±n/No = 1/(m1+m'(p))2 - 1/(m2+m'(s))2.

That is this equation will represent either a principal series or a diffuse series, depending on which of the m integers are assumed to be variable, when the value of 1 is assigned to the non-variable m-number. This is a first example of the Rydberg-Ritz combination principle.
Rydberg presented his conclusions in a seminar 1888. The work was published in the proceedings of the Royal Swedish Academy of Sciences in 1890, as "Recherches sur la constitution des spectres d'émission des éléments chimiques".

Fight for tenure

In 1897 K.A.V. Holmgren finally retired as professor at the age of 73. As is the custom in Sweden, the applications were reviewed by three outside experts: Christian Christiansen from the University of Copenhagen, Clas Bernard Hasselberg from KTH in Stockholm, and Knut Johan Ångström from Uppsala University. Christiansen's report came in first, it was short, recommending Rydberg as the first choice, declaring also P.G.D. Granqvist and C.A. Mebius competent, but excluding Victor Bäcklund from competition, because he was a mathematician.
Hasselberg and Ångström replied only after about a year. They both also said that Bäcklund could not be considered, and that Rydberg, Granqvist and Mebius were qualified. But they both ranked Rydberg last, because he had just ordered others' data, and hardly done experiments.
Christiansen warned Rydberg, who asked international collegues for letters of support. He received very supportive letters from Heinrich Kayser, Carl Runge, Ostwald, Eilhard Wiedemann, Walter Nernst, and others. These testimonials swayed the Greater Consistory of May 23rd 1900, and Rydberg's nomination was forwarded to the goverment. But then in September, Bäcklund was appointed!
Bäcklund was a personal friend of King Oscar II. There was reaction against this intervention in the press. Bäcklund used his influence to have Rydberg appointed to his previous position of extrardinary professor. The appointment came 15 March 1901. In 1908 a law was passed to abolish the extraordinary to ordinary professorships.

Final years

Janne Rydberg was nominated for the Nobel prize by Chalier, but it was never awarded to him. He did not even become a member of the Royals Swedish Academy of Sciences. In 1919, shortly before his death, he was elected a Foreign Member of the Royal Society of London. But he had been ill and unable to work since 1914. Janne Rydberg died on 28 December of a brain hemorrhage.

Sources:

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