Oscillator strengths of the principal series lines of Rb

The oscillator strengths of the principal series doublets of Rb 5 2 S 1/2 -n 2 P 3/2 and 5 2 S 1/2 -n 2 P 1/2 (6<or=n<or=20) have been measured in absorption using a high-resolution spectrometer. The absolute f values and the ratios of the doublet components rho =f 3/2 /f 1/2 are compared with available theoretical and other experimental results. At n=15 a pronounced perturbation in the monotonic increase of the oscillator strength ratio rho as a function of the principal quantum number n is found.