Fundamental series

The fundamental series is a set of spectra lines in a set caused by transition between d and f orbitals in atoms.

Originally the series was discovered in the infrared by Fowler and independently by Arno Bergmann. This resulted in the name Bergmann series used for such a set of lines in a spectrum. However the name was changed as Bergmann also discovered other series of lines. And other discoverers also established other such series. They became known as the fundamental series. Bergmann observed lithium at 5347 cm, sodium at 5416 cm potassium at 6592 cm. Bergmann observed that the lines in the series in the caesium spectrum were double. His discovery was announced in Contributions to the Knowledge of the Infra-Red Emission Spectra of the Alkalies, Jena 1907. Carl Runge called this series the "new series". He predicted that the lines of potassium and rubidium would be in pairs. He expressed the frequencies of the series lines by a formula and predicted a connection of the series limit to the other known series. In 1909 W. M. Hicks produced approximate formulas for the various series and noticed that this series had a simpler formula than the others and thus called it the "fundamental series" and used the letter F.