Oscillator strength measurements of the 3p → nd Rydberg transitions of sodium

We report new measurements of the oscillator strengths of the 3p P-2(3/2) -> nd D-2(5/2,3/2) and 3p P-2(1/2) -> nd D-2(3/2) Rydberg transitions of sodium using a thermionic diode ion detector in conjunction with the Nd:YAG pumped dye lasers. The ns S-2(1/2) and nd D-2(5/2,3/2) Rydberg series have been recorded via two-step excitation, from the 3p P-2(3/2) and 3p P-2(1/2) intermediate states. Employing the saturation technique, the photoionization cross sections from the 3p P-2(3/2) and 3p P-2(1/2) intermediate states at the. rst ionization threshold are determined as 7.9(1.3) Mb and 6.7(1.1) Mb respectively. The f-values of the Rydberg transitions are calibrated with the photoionization cross section measured at the first ionization threshold and compared with the earlier data.