Measurement of the SodiumD-Line Absolute Oscillator Strengths by the Roschdestvenskii Hook Method

The absolute oscillator strengths for the sodium $D$ lines have been measured using the Roschdestvenskii hook method, a technique which can provide an accurate means for measuring the product of the population and $f$ value, $\mathrm{Nf}$, for a gas. The experiment was performed under well-defined conditions, with a systematic variation of temperature, fringe angle, and fringe spacing. It was found that the $f$ values were independent of these variations in accordance with expectations. The measured $f$ values were $f_{D_2}=0.677\mathrm{}\pm 0.007$ and $f_{D_1}=0.341\mathrm{}\pm 0.009$. These results are in excellent agreement with the quantum-mechanical calculations which employ Bates-Damgaard or Hartree-Fock methods.